并发编程之锁--由浅到深！

清疚 2022-07-20 12:13 140阅读 0赞

http://blog.csdn.net/escaflone/article/details/10418651\#comments

**一、多线程**

**1、操作系统有两个容易混淆的概念，进程和线程。**

进程：一个计算机程序的运行实例，包含了需要执行的指令；有自己的独立地址空间，包含程序内容和数据；不同进程的地址空间是互相隔离的；进程拥有各种资源和状态信息，包括打开的文件、子进程和信号处理。

线程：表示程序的执行流程，是CPU调度执行的基本单位；线程有自己的程序计数器、寄存器、堆栈和帧。同一进程中的线程共用相同的地址空间，同时共享进进程锁拥有的内存和其他资源。

**2、Java标准库提供了进程和线程相关的API**，进程主要包括表示进程的java.lang.Process类和创建进程的java.lang.ProcessBuilder类；

表示线程的是java.lang.Thread类，在虚拟机启动之后，通常只有Java类的main方法这个普通线程运行，运行时可以创建和启动新的线程；还有一类守护线程（damon thread），守护线程在后台运行，提供程序运行时所需的服务。当虚拟机中运行的所有线程都是守护线程时，虚拟机终止运行。

**3、线程间的可见性：一个线程对进程中共享的数据的修改，是否对另一个线程可见**

可见性问题：

**a、CPU采用**时间片轮转**等不同算法来对线程进行调度**

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1.  **public** **class** IdGenerator\{  
2.     **private** **int** value = 0;  
3.     **public** **int** getNext()\{  
4.        **return** value++;  
5.     \}  
6.  \}

对于IdGenerator的getNext()方法，在多线程下不能保证返回值是不重复的：各个线程之间相互竞争CPU时间来获取运行机会，CPU切换可能发生在执行间隙。

以上代码getNext()的指令序列：CPU切换可能发生在7条指令之间，多个getNext的指令交织在一起。

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  aload\_0  
2.  dup  
3.  getfield \#12  
4.  dup\_x1  
5.  iconst\_1  
6.  iadd  
7.  putfield \#12

b、CPU缓存：

目前CPU一般采用层次结构的多级缓存的架构，有的CPU提供了L1、L2和L3三级缓存。当CPU需要读取主存中某个位置的数据时，会一次检查各级缓存中是否存在对应的数据。如果有，直接从缓存中读取，这比从主存中读取速度快很多。当CPU需要写入时，数据先被写入缓存中，之后再某个时间点写回主存。所以某些时间点上，缓存中的数据与主存中的数据可能是不一致。

**c、指令顺序重排**

出行性能考虑，编译器在编译时可能会对字节代码的指令顺序进行重新排列，以优化指令的执行顺序，在单线程中不会有问题，但在多线程可能产生与可见性相关的问题。

**二、Java内存模型（Java Memory Model）**

**屏蔽了CPU缓存等细节，只关注主存中的共享变量；关注对象的实例域、静态域和数组元素；关注线程间的动作。**

**1、volatile关键词**：用来对共享变量的访问进行同步，上一次写入操作的结果对下一次读取操作是肯定可见的。（在写入volatile变量值之后，CPU缓存中的内容会被写回内存；在读取volatile变量时，CPU缓存中的对应内容会被置为失效，重新从主存中进行读取），volatile不使用锁，性能优于synchronized关键词。---一致性

用来确保对一个变量的修改被正确地传播到其他线程中。

例子：A线程是Worker，一直跑循环，B线程调用setDone(true)，A线程即停止任务

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** Worker\{  
2.     **private** **volatile** **boolean** done;  
3.     **public** **void** setDone(**boolean** done)\{  
4.        **this**.done = done;  
5.     \}  
6.     **public** **void** work()\{  
7.        **while**(!done)\{  
8.           //执行任务；  
9.        \}  
10.    \}  
11. \}

例子：错误使用。因为没有锁的支持，volatile的修改不能依赖于当前值，当前值可能在其他线程中被修改。（Worker是直接赋新值与当前值无关）

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** Counter \{  
2.      **public** **volatile** **static** **int** count = 0;  
3.      **public** **static** **void** inc() \{  
4.          //这里延迟1毫秒，使得结果明显  
5.          **try** \{  
6.              Thread.sleep(1);  
7.          \} **catch** (InterruptedException e) \{  
8.          \}  
9.          count++;  
10.     \}  
11.     **public** **static** **void** main(String\[\] args) \{  
12.         //同时启动1000个线程，去进行i++计算，看看实际结果  
13.         **for** (**int** i = 0; i < 1000; i++) \{  
14.             **new** Thread(**new** Runnable() \{  
15.                 @Override  
16.                 **public** **void** run() \{  
17.                     Counter.inc();  
18.                 \}  
19.             \}).start();  
20.         \}  
21.         //这里每次运行的值都有可能不同,可能不为1000  
22.         System.out.println("运行结果:Counter.count=" + Counter.count);  
23.     \}  
24. \}

**2、final关键词**  
 final关键词声明的域的值只能被初始化一次，一般在构造方法中初始化。。（在多线程开发中，final域通常用来实现不可变对象）

当对象中的共享变量的值不可能发生变化时，在多线程中也就不需要同步机制来进行处理，故在多线程开发中应尽可能使用不可变对象。

另外，在代码执行时，final域的值可以被保存在寄存器中，而不用从主存中频繁重新读取。

**3、java基本类型的**原子操作

1）基本类型，引用类型的复制引用是原子操作；（即一条指令完成）

2）long与double的赋值，引用是可以分割的，非原子操作；

3）要在线程间共享long或double的字段时，必须在synchronized中操作，或是声明成volatile

**三、Java提供的线程同步方式**

**1、synchronized关键字**

方法或代码块的互斥性来完成实际上的一个原子操作。（方法或代码块在被一个线程调用时，其他线程处于等待状态）

所有的Java对象都有一个与synchronzied关联的监视器对象（monitor），允许线程在该监视器对象上进行加锁和解锁操作。

a、静态方法：Java类对应的Class类的对象所关联的监视器对象。

b、实例方法：当前对象实例所关联的监视器对象。

c、代码块：代码块声明中的对象所关联的监视器对象。

注：当锁被释放，对共享变量的修改会写入主存；当活得锁，CPU缓存中的内容被置为无效。编译器在处理synchronized方法或代码块，不会把其中包含的代码移动到synchronized方法或代码块之外，从而避免了由于代码重排而造成的问题。

例：以下方法getNext()和getNextV2() 都获得了当前实例所关联的监视器对象

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1.  **public** **class** SynchronizedIdGenerator\{  
2.     **private** **int** value = 0;  
3.     **public** **synchronized** **int** getNext()\{  
4.        **return** value++;  
5.     \}  
6.     **public** **int** getNextV2()\{  
7.        **synchronized**(**this**)\{  
8.           **return** value++;  
9.        \}  
10.    \}  
11. \}

**2、Object类的wait、notify和notifyAll方法 **

生产者和消费者模式，判断缓冲区是否满来消费，缓冲区是否空来生产的逻辑。如果用while 和 volatile也可以做，不过本质上会让线程处于忙等待，占用CPU时间，对性能造成影响。

wait： 将当前线程放入，该对象的等待池中，线程A调用了B对象的wait()方法，线程A进入B对象的等待池，并且释放B的锁。（这里，线程A必须持有B的锁，所以调用的代码必须在synchronized修饰下，否则直接抛出java.lang.IllegalMonitorStateException异常）。

notify：将该对象中等待池中的线程，随机选取一个放入对象的锁池，当当前线程结束后释放掉锁， 锁池中的线程即可竞争对象的锁来获得执行机会。

notifyAll：将对象中等待池中的线程，全部放入锁池。

（notify锁唤醒的线程选择由虚拟机实现来决定，不能保证一个对象锁关联的等待集合中的线程按照所期望的顺序被唤醒，很可能一个线程被唤醒之后，发现他所要求的条件并没有满足，而重新进入等待池。因为当等待池中包含多个线程时，一般使用notifyAll方法，不过该方法会导致线程在没有必要的情况下被唤醒，之后又马上进入等待池，对性能有影响，不过能保证程序的正确性）

工作流程：

a、Consumer线程A 来 看产品，发现产品为空，调用产品对象的wait()，线程A进入产品对象的等待池并释放产品的锁。

b、Producer线程B获得产品的锁，执行产品的notifyAll()，Consumer线程A从产品的等待池进入锁池，Producer线程B生产产品，然后退出释放锁。

c、Consumer线程A获得产品锁，进入执行，发现有产品，消费产品，然后退出。

例子：

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1.  **public** **synchronized** String pop()\{  
2.    **this**.notifyAll();// 唤醒对象等待池中的所有线程，可能唤醒的就是 生产者（当生产者发现产品满，就会进入对象的等待池，这里代码省略，基本略同）  
3.     **while**(index == -1)\{ //如果发现没产品，就释放锁，进入对象等待池  
4.        **this**.wait();  
5.     \}//当生产者生产完后，消费者从this.wait()方法再开始执行，第一次还会执行循环，万一产品还是为空，则再等待，所以这里必须用while循环，不能用if  
6.     String good = buffer\[index\];  
7.     buffer\[index\] = **null**;  
8.     index--;  
9.     **return** good;// 消费完产品，退出。  
10. \}

注：wait()方法有超时和不超时之分，超时的在经过一段时间，线程还在对象的等待池中，那么线程也会推出等待状态。

**3、线程状态转换：**

已经废弃的方法：stop、suspend、resume、destroy，这些方法在实现上时不安全的。

线程的状态：NEW、RUNNABLE、BLOCKED、WAITING、TIMED\_WAITING（有超时的等待）、TERMINATED。

a、方法sleep()进入的阻塞状态，不会释放对象的锁（即大家一起睡，谁也别想执行代码），所以不要让sleep方法处在synchronized方法或代码块中，否则造成其他等待获取锁的线程长时间处于等待。

b、方法join()则是主线程等待子线程完成，再往下执行。例如main方法新建两个线程A和B

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1.  **public** **static** **void** main(String\[\] args) **throws** InterruptedException \{    
2.  Thread t1 = **new** Thread(**new** ThreadTesterA());    
3.  Thread t2 = **new** Thread(**new** ThreadTesterB());    
4.  t1.start();    
5.  t1.join(); // 等t1执行完再往下执行  
6.  t2.start();    
7.  t2.join(); // 在虚拟机执行中，这句可能被忽略  
8.  \}

c、方法interrupt()，向被调用的对象线程发起中断请求。如线程A通过调用线程B的d的interrupt方法来发出中断请求，线程B来处理这个请求，当然也可以忽略，这不是必须的。Object类的wait()、Thread类的join()和sleep方法都会抛出受检异常java.lang.InterruptedException，通过interrupt方法中断该线程会导致线程离开等待状态。对于wait()调用来说，线程需要重新获取监视器对象上的锁之后才能抛出InterruptedException异常，并致以异常的处理逻辑。

可以通过Thread类的isInterrupted方法来判断是否有中断请求发生，通常可以利用这个方法来判断是否退出线程（类似上面的volatitle修饰符的例子）；

Thread类还有个方法Interrupted()，该方法不但可以判断当前线程是否被中断，还会清楚线程内部的中断标记，如果返回true，即曾被请求中断，同时调用完后，清除中断标记。

如果一个线程在某个对象的等待池，那么notify和interrupt 都可以使该线程从等待池中被移除。如果同时发生，那么看实际发生顺序。如果是notify先，那照常唤醒，没影响。如果是interrupt先，并且虚拟机选择让该线程中断，那么即使nofity，也会忽略该线程，而唤醒等待池中的另一个线程。

e、yield()，尝试让出所占有的CPU资源，让其他线程获取运行机会，对操作系统上的调度器来说是一个信号，不一定立即切换线程。（在实际开发中，测试阶段频繁调用yeid方法使线程切换更频繁，从而让一些多线程相关的错误更容易暴露出来）。

![20130828010551062][]

**四、非阻塞方式**

线程之间同步机制的核心是监视对象上的锁，竞争锁来获得执行代码的机会。当一个对象获取对象的锁，然后其他尝试获取锁的对象会处于等待状态，这种锁机制的实现方式很大程度限制了多线程程序的吞吐量和性能（线程阻塞），且会带来死锁（线程A有a对象锁，等着获取b对象锁，线程B有b对象锁，等待获取a对象锁）和优先级倒置（优先级低的线程获得锁，优先级高的只能等待对方释放锁）等问题。

如果能不阻塞线程，又能保证多线程程序的正确性，就能有更好的性能。

在程序中，对共享变量的使用一般遵循一定的模式，即读取、修改和写入三步组成。之前碰到的问题是，这三步执行中可能线程执行切换，造成非原子操作。锁机制是把这三步变成一个原子操作。

目前CPU本身实现 将这三步 合起来 形成一个原子操作，无需线程锁机制干预，常见的指令是“比较和替换”（compare and swap,CAS），这个指令会先比较某个内存地址的当前值是不是指定的旧指，如果是，就用新值替换，否则什么也不做，指令返回的结果是内存地址的当前值。通过CAS指令可以实现不依赖锁机制的非阻塞算法。一般做法是把CAS指令的调用放在一个无限循环中，不断尝试，知道CAS指令成功完成修改。

java.util.concurrent.atomic包中提供了CAS指令。（不是所有CPU都支持CAS，在某些平台，java.util.concurrent.atomic的实现仍然是锁机制）

**atomic包中提供的Java类分成三类：**

**1、支持以原子操作来进行更新的数据类型的Java类**（AtomicBoolean、AtomicInteger、AtomicReference），在内存模型相关的语义上，这四个类的对象类似于volatile变量。

类中的常用方法：

a、compareAndSet：接受两个参数，一个是期望的旧值，一个是替换的新值。

b、weakCompareAndSet：效果同compareAndSet（JSR中表示weak原子方式读取和有条件地写入变量但不创建任何 happen-before 排序，但在源代码中和compareAndSet完全一样，所以并没有按JSR实现）

c、get和set：分别用来直接获取和设置变量的值。

d、lazySet：与set类似，但允许编译器把lazySet方法的调用与后面的指令进行重排，因此对值得设置操作有可能被推迟。

例：

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1.  **public** **class** AtomicIdGenerator\{  
2.     **private** **final** AtomicInter counter = **new** AtomicInteger(0);  
3.     **public** **int** getNext()\{  
4.        **return** counter.getAndIncrement();  
5.     \}  
6.  \}  
7.  // getAndIncrement方法的内部实现方式，这也是CAS方法的一般模式，CAS方法不一定成功，所以包装在一个无限循环中，直到成功  
8.  **public** **final** **int** getAndIncrement()\{  
9.     **for**(;;)\{  
10.       **int** current = get();  
11.       **int** next = current +1;  
12.       **if**(compareAndSet(current,next))  
13.          **return** current;  
14.    \}  
15. \}

2、**提供对数组类型的变量进行处理的Java类**，AtomicIntegerArray、AtomicLongArray和AtomicReferenceArray类。（同上，只是放在类数组里，调用时也只是多了一个操作元素索引的参数）

**3、通过反射的方式对任何对象中包含的volatitle变量使用CAS方法**，AtomicIntegerFieldUpdater、AtomicLongFieldUpdater、AtomicReferenceFieldUpdater。他们提供了一种方式把CAS的功能扩展到了任何Java类中声明为volatitle的域上。（灵活，但语义较弱，因为对象的volatitle可能被非atomic的其他方式被修改）

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1.  **public** **class** TreeNode\{  
2.     **private** **volatile** TreeNode parent;  
3.  // 静态工厂方法  
4.     **private** **static** **final** AtomicReferenceFieldUpdater<TreeNode, TreeNode> parentUpdater = AtomicReferenceFieldUpdater.newUpdater(TreeNode.**class**,TreeNode.**class**,"parent");  
5.  **public** **boolean** compareAndSetParent(TreeNode expect, TreeNode update)\{  
6.        **return** parentUpdater.compareAndSet(**this**, expect, update);  
7.  \}  
8.  \}

注：java.util.concurrent.atomic包中的Java类属于比较底层的实现，一般作为java.util.concurrent包中很多非阻塞的数据结构的实现基础。

比较多的用AtomicBoolean、AtomicInteger、AtomicLong和AtomicReference。在实现线程安全的计数器时，AtomicInteger和AtomicLong类时最佳的选择。

**五、高级同步机制（比synchronized更灵活的加锁机制）**

synchronized和volatile，以及wait、notify等方法抽象层次低，在程序开发中使用比较繁琐，易出错。

而多线程之间的交互来说，存在某些固定的模式，如生产者-消费者和读者-写者模式，把这些模式抽象成高层API，使用起来会非常方便。

java.util.concurrent包为多线程提供了高层的API，满足日常开发中的常见需求。

常用接口

**1、Lock接口，表示一个锁方法：**

a、lock()，获取所，如果无法获取所锁，会处于等待状态

b、unlock()，释放锁。（一般放在finally代码块中）

c、lockInterruptibly()，与lock()类似，但允许当前线程在等待获取锁的过程中被中断。（所以要处理InterruptedException）

d、tryLock()，以非阻塞方式获取锁，如果无法获取锁，则返回false。（tryLock()的另一个重载可以指定超时，如果指定超时，当无法获取锁，会等待而阻塞，同时线程可以被中断）

**2、ReadWriteLock接口，表示两个锁，读取的共享锁和写入的排他锁。（适合常见的读者--写者场景）**

ReadWriteLock接口的readLock和writeLock方法来获取对应的锁的Lock接口的实现。

在多数线程读取，少数线程写入的情况下，可以提高多线程的性能，提高使用该数据结构的吞吐量。

如果是相反的情况，较多的线程写入，则接口会降低性能。

**3、ReentrantLock类和ReentrantReadWriteLock，分别为上面两个接口的实现类。**

他们具有重入性：即允许一个线程多次获取同一个锁（他们会记住上次获取锁并且未释放的线程对象，和加锁的次数，getHoldCount()）

同一个线程每次获取锁，加锁数+1，每次释放锁，加锁数-1，到0，则该锁被释放，可以被其他线程获取。

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** LockIdGenrator\{  
2.  //new ReentrantLock(true)是重载，使用更加公平的加锁机制，在锁被释放后，会优先给等待时间最长的线程，避免一些线程长期无法获得锁  
3.     **private** **int** ReentrantLock lock = ReentrantLock();  
4.     privafte **int** value = 0;  
5.     **public** **int** getNext()\{  
6.        lock.lock();      //进来就加锁，没有锁会等待  
7.        **try**\{  
8.           **return** value++;//实际操作  
9.        \}**finally**\{  
10.          lock.unlock();//释放锁  
11.       \}  
12.    \}  
13. \}

注：重入性减少了锁在各个线程之间的等待，例如便利一个HashMap，每次next()之前加锁，之后释放，可以保证一个线程一口气完成便利，而不会每次next()之后释放锁，然后和其他线程竞争，降低了加锁的代价， 提供了程序整体的吞吐量。（即，让一个线程一口气完成任务，再把锁传递给其他线程）。  
4、Condition接口，Lock接口代替了synchronized，Condition接口替代了object的wait、nofity。

a、await()，使当前线程进入等待状态，知道被唤醒或中断。重载形式可以指定超时时间。

b、awaitNanos()，以纳秒为单位等待。

c、awaitUntil()，指定超时发生的时间点，而不是经过的时间，参数为java.util.Date。

d、awaitUninterruptibly()，前面几种会响应其他线程发出的中断请求，他会无视，直到被唤醒。

注：与Object类的wait()相同，await()会释放其所持有的锁。

e、signal()和signalAll， 相当于 notify和notifyAll

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  Lock lock = **new** ReentrantLock();  
2.  Condition condition = lock.newCondition();  
3.  lock.lock();  
4.  **try**\{  
5.     **while**(/\*逻辑条件不满足\*/)\{  
6.        condition.await();     
7.     \}  
8.  \}**finally**\{  
9.     lock.unlock();  
10. \}

**六、底层同步器**

多线程程序中，线程之间存在多种不同的同步方式。除了Java标准库提供的同步方式之外，程序中特有的同步方式需要由开发人员自己来实现。

常见的一种需求是 对有限个共享资源的访问，比如多台个人电脑，2台打印机，当多个线程在等待同一个资源时，从公平角度出发，会用FIFO队列。

如果程序中的同步方式可以抽象成对有限个资源的访问，那么可以使用java.util.concurrent.locks包中的AbstractQueuedSynchronizer类和AbstractQueuedLongSynchronizer类作为实现的基础，前者用int类型的变量来维护内部状态，而后者用long类型。（可以将这个变量理解为共享资源个数）

通过getState、setState、和compareAndSetState3个方法更新内部变量的值。

AbstractQueuedSynchronizer类是abstract的，需要覆盖其中包含的部分方法，通常做法是把其作为一个Java类的内部类，外部类提供具体的同步方式，内部类则作为实现的基础。有两种模式，排他模式和共享模式，分别对应方法 tryAcquire()、tryRelease 和 tryAcquireShared、tryReleaseShared，在这些方法中，使用getState、setState、compareAndSetState3个方法来修改内部变量的值，以此来反应资源的状态。

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** SimpleResourceManager\{  
2.     **private** **final** InnerSynchronizer synchronizer;  
3.     **private** **static** **class** InnerSynchronizer **extends** AbstractQueuedSynchronizer\{  
4.        InnerSynchronizer(**int** numOfResources)\{  
5.           setState(numOfResources);  
6.        \}  
7.        **protected** **int** tryAcquireShared(**int** acquires)\{  
8.           **for**(;;)\{  
9.              **int** available = getState();  
10.             **int** remain = available - acquires;  
11.             **if**(remain <0 || comapreAndSetState(available, remain)\{  
12.                **return** remain;  
13.             \}  
14.          \}  
15.       \}  
16.       **protected** **boolean** **try** ReleaseShared(**int** releases)\{  
17.          **for**(;;)\{  
18.             **int** available = getState();   
19.             **int** next = available + releases;   
20.             **if**(compareAndSetState(available,next)\{  
21.                **return** **true**;  
22.             \}  
23.          \}  
24.       \}  
25.    \}  
26.    **public** SimpleResourceManager(**int** numOfResources)\{  
27.       synchronizer = **new** InnerSynchronizer(numOfResources);  
28.    \}  
29.    **public** **void** acquire() **throws** InterruptedException\{  
30.       synchronizer.acquireSharedInterruptibly(1);  
31.    \}        
32.    pubic **void** release()\{      
33.       synchronizer.releaseShared(1);  
34.     \}  
35. \}

**七、高级同步对象（提高开发效率）**

atomic和locks包提供的Java类可以满足基本的互斥和同步访问的需求，但这些Java类的抽象层次较低，使用比较复杂。

更简单的做法是使用java.util.concurrent包中的高级同步对象。

**1、信号量。**

信号量一般用来数量有限的资源，每类资源有一个对象的信号量，信号量的值表示资源的可用数量。

在使用资源时，需要从该信号量上获取许可，成功获取许可，资源的可用数-1；完成对资源的使用，释放许可，资源可用数+1； 当资源数为0时，需要获取资源的线程以阻塞的方式来等待资源，或过段时间之后再来检查资源是否可用。（上面的SimpleResourceManager类实际上时信号量的一个简单实现）

java.util.concurrent.Semaphore类，在创建Semaphore类的对象时指定资源的可用数

a、acquire()，以阻塞方式获取许可

b、tryAcquire()，以非阻塞方式获取许可

c、release()，释放许可。

d、accquireUninterruptibly()，accquire()方法获取许可以的过程可以被中断，如果不希望被中断，使用此方法。

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** PrinterManager\{  
2.     **private** **final** Semphore semaphore;  
3.     **private** **final** List<Printer> printers = **new** ArrayList<>():  
4.     **public** PrinterManager(Collection<? **extends** Printer> printers)\{  
5.        **this**.printers.addAll(printers);  
6.        //这里重载方法，第二个参数为true，以公平竞争模式，防止线程饥饿  
7.        **this**.semaphore = **new** Semaphore(**this**.printers.size(),**true**);  
8.     \}  
9.     **public** Printer acquirePrinter() **throws** InterruptedException\{  
10.       semaphore.acquire();  
11.       **return** getAvailablePrinter();  
12.    \}  
13.    **public** **void** releasePrinter(Printer printer)\{  
14.       putBackPrinter(pinter);  
15.       semaphore.release();  
16.    \}  
17.    **private** **synchronized** Printer getAvailablePrinter()\{  
18.       printer result = printers.get(0);  
19.       printers.remove(0);  
20.       **return** result;  
21.    \}  
22.    **private** **synchronized** **void** putBackPrinter(Printer printer)\{  
23.       printers.add(printer);  
24.    \}  
25. \}

**2、倒数闸门**

多线程协作时，一个线程等待另外的线程完成任务才能继续进行。

java.util.concurrent.CountDownLatch类，创建该类时，指定等待完成的任务数；当一个任务完成，调用countDonw()，任务数-1。等待任务完成的线程通过await()，进入阻塞状态，直到任务数量为0。CountDownLatch类为一次性，一旦任务数为0，再调用await()不再阻塞当前线程，直接返回。

例：

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** PageSizeSorter\{  
2.     // 并发性能远远优于HashTable的 Map实现，hashTable做任何操作都需要获得锁，同一时间只有有个线程能使用，而ConcurrentHashMap是分段加锁，不同线程访问不同的数据段，完全不受影响，忘记HashTable吧。  
3.     **private** **static** **final** ConcurrentHashMap<String , Interger> sizeMap = **new** ConcurrentHashMap<>();  
4.     **private** **static** **class** GetSizeWorker **implements** Runnable\{  
5.        **private** **final** String urlString;  
6.        **public** GetSizeWorker(String urlString , CountDownLatch signal)\{  
7.           **this**.urlString = urlStirng;  
8.           **this**.signal = signal;  
9.        \}  
10.       **public** **void** run()\{  
11.          **try**\{  
12.             InputStream is = **new** URL(urlString).openStream();  
13.             **int** size = IOUtils.toByteArray(is).length;  
14.             sizeMap.put(urlString, size);  
15.          \}**catch**(IOException e)\{  
16.             sizeMap.put(urlString, -1);  
17.          \}**finally**\{  
18.             signal.countDown()://完成一个任务 ， 任务数-1  
19.          \}  
20.       \}  
21.    \}  
22.    **private** **void** sort()\{  
23.       List<Entry<String, Integer> list = **new** ArrayList<sizeMap.entrySet());  
24.       Collections.slort(list, **new** Comparator<Entry<String,Integer>>()\{  
25.          **public** **int** compare (Entry<String, Integer> o1, Entry<Sting , Integer> o2)\{  
26.             **return** Integer.compare(o2.getValue(),o1.getValue());  
27.       \};  
28.       System.out.println(Arrays.deepToString(list.toArray()));  
29.    \}  
30.    **public** **void** sortPageSize(Collection<String> urls) **throws** InterruptedException\{  
31.       CountDownLatch sortSignal = **new** CountDownLatch(urls.size());  
32.       **for**(String url: urls)\{  
33.          **new** Thread(**new** GetSizeWorker(url, sortSignal)).start();  
34.       \}  
35.       sortSignal.await()://主线程在这里等待，任务数归0，则继续执行  
36.       sort();  
37.    \}  
38. \}

**3、循环屏障**

循环屏障在作用上类似倒数闸门，不过他不像倒数闸门是一次性的，可以循环使用。另外，线程之间是互相平等的，彼此都需要等待对方完成，当一个线程完成自己的任务之后，等待其他线程完成。当所有线程都完成任务之后，所有线程才可以继续运行。

当线程之间需要再次进行互相等待时，可以复用同一个循环屏障。

类java.uti.concurrent.CyclicBarrier用来表示循环屏障，创建时指定使用该对象的线程数目，还可以指定一个Runnable接口的对象作为每次循环后执行的动作。（当最后一个线程完成任务之后，所有线程继续执行之前，被执行。如果线程之间需要更新一些共享的内部状态，可以利用这个Runnalbe接口的对象来处理）。

每个线程任务完成之后，通过调用await方法进行等待，当所有线程都调用await方法之后，处于等待状态的线程都可以继续执行。在所有线程中，只要有一个在等待中被中断，超时或是其他错误，整个循环屏障会失败，所有等待中的其他线程抛出java.uti.concurrent.BrokenBarrierException。

例：每个线程负责找一个数字区间的质数，当所有线程完成后，如果质数数目不够，继续扩大范围查找

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** PrimeNumber\{  
2.     **private** **static** **final** **int** TOTAL\_COUTN = 5000;  
3.     **private** **static** **final** **int** RANGE\_LENGTH= 200;  
4.     **private** **static** **final** **int** WORKER\_NUMBER = 5;  
5.     **private** **static** volatitle **boolean** done = **false**;  
6.     **private** **static** **int** rangeCount = 0;  
7.     **private** **static** **final** List<Long> results = **new** ArrayList<Long>():  
8.     **private** **static** **final** CyclicBarrier barrier = **new** CyclicBarrier(WORKER\_NUMBER, **new** Runnable()\{  
9.        **public** **void** run()\{  
10.          **if**(results.size() >= TOTAL\_COUNT)\{  
11.             done = **true**;  
12.          \}  
13.      \}  
14.    \});  
15.    **private** **static** **class** PrimeFinder **implements** Runnable\{  
16.       **public** **void** run()\{  
17.          **while**(!done)\{ // 整个过程在一个 while循环下，await()等待，下次循环开始，会再次判断 执行条件  
18.             **int** range = getNextRange();  
19.             **long** start = rang \* RANGE\_LENGTH;  
20.             **long** end = (range + 1) \* RANGE\_LENGTH;  
21.             **for**(**long** i = start; i<end;i++)\{  
22.                **if**(isPrime(i))\{  
23.                   updateResult(i);  
24.                \}  
25.             \}  
26.             **try**\{  
27.                barrier.await();  
28.             \}**catch** (InterruptedException | BokenBarrierException e)\{  
29.                done =  **true**;  
30.             \}  
31.          \}  
32.       \}  
33.    \}  
34.    **private** **synchronized** **static** **void** updateResult(**long** value)\{  
35.       results.add(value);  
36.    \}  
37.    **private** **synchronized** **static** **int** getNextRange()\{  
38.       **return** rangeCount++;  
39.    \}  
40.    **private** **static** **boolean** isPrime(**long** number)\{  
41.       //找质数的代码  
42.    \}  
43.    **public** **void** calculate()\{  
44.       **for**(**int** i=0;i<WORKER\_NUMBER;i++)\{  
45.          **new** Thread(**new** PrimeFinder()).start();  
46.       \}  
47.       **while**(!done)\{  
48.   
49.       \}  
50.       //计算完成  
51.    \}  
52. \}

**4、对象交换器**  
 适合于两个线程需要进行数据交换的场景。（一个线程完成后，把结果交给另一个线程继续处理）

java.util.concurrent.Exchanger类，提供了这种对象交换能力，两个线程共享一个Exchanger类的对象，一个线程完成对数据的处理之后，调用Exchanger类的exchange()方法把处理之后的数据作为参数发送给另外一个线程。而exchange方法的返回结果是另外一个线程锁提供的相同类型的对象。如果另外一个线程未完成对数据的处理，那么exchange()会使当前线程进入等待状态，直到另外一个线程也调用了exchange方法来进行数据交换。

例：

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** SendAndReceiver\{  
2.     **private** **final** Exchanger<StringBuilder> exchanger = **new** Exchanger<StringBuilder>();  
3.     **private** **class** Sender **implements** Runnable\{  
4.        **public** **void** run()\{  
5.           **try**\{  
6.              StringBuilder content = **new** StringBuilder("Hello");  
7.              content = exchanger.exchange(content);  
8.           \}**catch**(InterruptedException e)\{  
9.              Thread.currentThread().interrupt();  
10.          \}  
11.       \}  
12.    \}  
13.    **private** **class** Receiver **implements** Runnable\{  
14.       **public** **void** run()\{  
15.          **try**\{  
16.             StringBuilder content = **new** StringBuilder("World");  
17.             content = exchanger.exchange(content);  
18.          \}**catch**(InterruptedException e)\{  
19.             Thread.currentThread().interrupt();  
20.          \}  
21.       \}  
22.    \}  
23.    **public** **void** exchange()\{  
24.       **new** Thread(**new** Sender()).start();  
25.       **new** Thread(**new** Receiver()).start();  
26.    \}  
27. \}

八、数据结构（多线程程序使用的高性能数据结构）

java.util.concurrent包中提供了一些适合多线程程序使用的高性能数据结构，包括队列和集合类对象等。

**1、队列**

**a、BlockingQueue接口**：线程安全的阻塞式队列；当队列已满时，想队列添加会阻塞；当队列空时，取数据会阻塞。（非常适合消费者-生产者模式）

阻塞方式：put()、take()。

非阻塞方式：offer()、poll()。

实现类：基于数组的固定元素个数的**ArrayBolockingQueue**和基于链表结构的不固定元素个数的**LinkedBlockQueue**类。

**b、BlockingDeque接口**： 与BlockingQueue相似，但可以对头尾进行添加和删除操作的双向队列；方法分为两类，分别在队首和对尾进行操作。

实现类：标准库值提供了一个基于链表的实现，**LinkedBlockgingDeque**。

2、集合类

在多线程程序中，如果共享变量时集合类的对象，则不适合直接使用java.util包中的集合类。这些类要么不是线程安全，要么在多线程下性能比较差。

应该使用java.util.concurrent包中的集合类。

**a、ConcurrentMap接口**： 继承自java.util.Map接口

putIfAbsent()：只有在散列表不包含给定键时，才会把给定的值放入。

remove()：删除条目。

replace(key,value)：把value 替换到给定的key上。

replace(key, oldvalue, newvalue)：CAS的实现。

实现类：**ConcurrentHashMap**：

创建时，如果可以预估可能包含的条目个数，可以优化性能。（因为动态调整所能包含的数目操作比较耗时，这个HashMap也一样，只是多线程下更耗时）。

创建时，预估进行更新操作的线程数，这样实现中会根据这个数把内部空间划分为对应数量的部分。（默认是16，如果只有一个线程进行写操作，其他都是读取，那么把值设为1 可以提高性能）。

注：当从集合中创建出迭代器遍历Map元素时，不一定能看到正在添加的数据，只能和集合保证弱一致性。（当然使用迭代器不会因为查看正在改变的Map，而抛出java.util.ConcurrentModifycationException）

**b、CopyOnWriteArrayList接口**：继承自java.util.List接口。

顾名思义，在CopyOnWriteArrayList的实现类，所有对列表的更新操作都会新创建一个底层数组的副本，并使用副本来存储数据；对列表更新操作加锁，读取操作不加锁。

适合多读取少修改的场景，如果更新操作多，那么不适合用，同样迭代器只能表示创建时列表的状态，更新后使用了新的底层数组，迭代器还是引用旧的底层数组。

**九、多线程任务的执行**

**过去线程的执行，是先创建Thread类的想，再调用start方法启动，这种做法要求开发人员对线程进行维护，在线程较多时，一般创建一个线程池同一管理，同时降低重复创建线程的开销**

在J2SE5.0中，java.util.concurrent包提供了丰富的用来管理线程和执行任务的实现。

**1、基本接口（描述任务）**

a、Callable接口：

Runnable接口受限于run方法的类型签名，而Callable只有一个方法call()，可以有返回值，可以抛出受检异常。

b、Future接口：

过去，需要异步线程的任务执行结果，要求主线程和任务执行线程之间进行同步和数据传递。

Future简化了任务的异步执行，作为异步操作的一个抽象。调用get()方法可以获取异步的执行结果，如果任务没有执行完，会等待，直到任务完成或被取消，cancel()可以取消。

c、Delayed接口：

延迟执行任务，getDelay()返回当前剩余的延迟时间，如果不大于0，说明延迟时间已经过去，应该调度并执行该任务。

**2、组合接口（描述任务）**

a、RunnableFuture接口：继承自Runnable接口和Future接口。

当来自Runnalbe接口中的run方法成功执行之后，相当于Future接口表示的异步任务已经完成，可以通过get()获取运行结果。

b、ScheduledFuture接口：继承Future接口和Delayed接口，表示一个可以调用的异步操作。

c、RunnableScheduledFuture接口：继承自Runnable、Delayed和Future，接口中包含isPeriodic，表明该异步操作是否可以被重复执行。

**3、Executor接口、ExcutorServer接口、ScheduleExecutorService接口和CompletionService接口（描述任务执行）**

a、executor接口，execute()用来执行一个Runnable接口的实现对象，不同的Executor实现采取不同执行策略，但提供的任务执行功能比较弱。

b、excutorServer接口，继承自executor；

提供了对任务的管理：submit()，可以吧Callable和Runnable作为任务提交，得到一个Future作为返回，可以获取任务结果或取消任务。

提供批量执行：invokeAll()和invokeAny()，同时提交多个Callable；invokeAll()，会等待所有任务都执行完成，返回一个包含每个任务对应Future的列表；invokeAny()，任何一个任务成功完成，即返回该任务结果。

提供任务关闭：shutdown()、shutdownNow()来关闭服务，前者不允许新的任务提交，后者试图终止正在运行和等待的任务，并返回已经提交单没有被运行的任务列表。（两个方法都不会等待服务真正关闭，只是发出关闭请求。）。shutdownDow，通常做法是向线程发出中断请求，所以确保提交的任务实现了正确的中断处理逻辑。

c、ScheduleExecutorService接口，继承自excutorServer接口：支持任务的延迟执行和定期执行，可以执行Callable或Runnable。

schedule()，调度一个任务在延迟若干时间之后执行；

scheduleAtFixedRate()：在初始延迟后，每隔一段时间循环执行；在下一次执行开始时，上一次执行可能还未结束。（同一时间，可能有多个）

scheduleWithFixedDelay：同上，只是在上一次任务执行完后，经过给定的间隔时间再开始下一次执行。（同一时间，只有一个）

以上三个方法都返回ScheduledFuture接口的实现对象。

d、CompletionService接口，共享任务执行结果。

通常在使用ExecutorService接口，通过submit提交任务，并得到一个Future接口来获取任务结果，如果任务提交者和执行结果的使用者是程序的不同部分，那就要把Future在不同部分进行传递；而CompletionService就是解决这个问题，程序不同部分可以共享CompletionService，任务提交后，执行结果可以通过take（阻塞），poll（非阻塞）来获取。

标准库提供的实现是 ExecutorCompletionService，在创建时，需要提供一个Executor接口的实现作为参数，用来实际执行任务。

例：多线程方式下载文件

**\[java\]**  [view plain][]   [copy][view plain]

[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** FileDownloader\{  
2.     // 线程池  
3.     **private** **final** ExecutorService executor = Executors.newFixedThreadPool(10);  
4.     **public** **boolean** download(**final** URL url, **final** Path path)\{  
5.     Future<Path> future = executor.submit(**new** Callable<Path>()\{ //submit提交任务  
6.        **public** Path call()\{  
7.           //这里就省略IOException的处理了  
8.           InputStream is = url.openStream();  
9.           Files.copy(is, path, StandardCopyOption.REPLACE\_EXISTING);  
10.          **return** path;  
11.       \});  
12.       **try**\{  
13.          **return** future.get() !=**null** ? **true** : **false**;  
14.       \}<span style="font-family: Arial, Helvetica, sans-serif;">**catch**(InterruptedException | ExecutionException e)\{</span>  
15.              **return** **false**;  
16.       \}  
17.    \}  
18.    **public** **void** close()\{ //当不再使用FileDownloader类的对象时，应该使用close方法关闭其中包含的ExecutorService接口的实现对象，否则虚拟机不会退出，占用内存不释放  
19.       executor.shutdown();// 发出关闭请求，此时不会再接受新任务  
20.       **try**\{  
21.          **if**(!executor.awaitTermination(3, TimeUnit.MINUTES))\{ // awaitTermination 来等待一段时间，使正在执行的任务或等待的任务有机会完成  
22.             executor.shutdownNow();// 如果等待时间过后还有任务没完成，则强制结束  
23.             executor.awaitTermination(1, TimeUnit.MINUTES);// 再等待一段时间，使被强制结束的任务完成必要的清理工作  
24.          \}  
25.       \}**catch**(InterruptedException e)\{  
26.          executor.shutdownNow();  
27.          Thread.currentThread().interrupt();  
28.       \}  
29.    \}  
30. \}

**十、[Java SE][] 7 新特性**

对java.util.concurrent包进行更新，增加了新的轻量级任务执行框架fork/join和多阶段线程同步工具。

**1、轻量级任务执行框架fork/join**

这个框架的目的主要是更好地利用底层平台上的**多核和多处理器来进行并行处理。**

通过**分治算法或map/reduce算法来解决问题。**

fork/join 类比于 map/reduce。

fork操作是把一个大的问题划分为若干个较小的问题，划分过程一般为递归，直到可以直接进行计算的粒度适合的子问题；子问题在结算后，可以得到整个问题的部分解

join操作收集子结果，合并，得到完整解，也可能是 递归进行的。

相对一般的线程池实现，F/J框架的优势在任务的处理方式上。在一般线程池中，一个线程由于某些原因无法运行，会等待；而在F/J，某个子问题由于等待另外一个子问题的完成而无法继续运行，那么处理该子问题的线程会主动寻找其他尚未运行的子问题来执行。这种方式减少了等待时间，提高了性能。

为了F/J能高效，在每个子问题视线中应避免使用synchronized或其他方式进行同步，也不应使用阻塞式IO或过多访问共享变量。在理想情况下，每个子问题都应值进行CPU计算，只使用每个问题的内部对象，唯一的同步应只发生在子问题和创建它的父问题之间。（这完全就是Hadoop的MapReduce嘛）

**a、ForkJoinTask类**：表示一个由F/J框架执行的任务，该类实现了Future接口，可以按照Future接口的方式来使用。（表示任务）

fork()，异步方式启动任务的执行。

join()，等待任务完成并返回执行结果。

在创建自己的任务时，最好不要直接继承自ForkJoinTask，而是继承其子类，RecuriveTask或RecursiveAction，前者可以返回结果，后者不行。

**b、ForkJoinPool类**：表示任务执行，实现了ExecutorService接口，除了可以执行ForkJoinTask，也可以执行Callable和Runnable。（任务执行）

执行任务的两大类：

第一类：execute、invoke或submit方法：直接提交任务。

第二类：fork()：运行ForkJoinTask在执行过程中的子任务。

一般作法是表示整个问题的ForkJoinTask用第一类提交，执行过程中产生的子任务不需要处理，ForkJoinPool会负责子任务执行。

例：查找数组中的最大值

**\[java\]**  [view plain][]   [copy][view plain]

[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **private** **static** **class** MaxValueTask **extends** RecursiveTask<Long>\{  
2.     **private** **final** **long**\[\] array;  
3.     **private** **final** **int** start;  
4.     **private** **final** **int** end;  
5.     MaxValueTask(**long**\[\] array, **int** start, **int** end)\{  
6.        **this**.array = array;  
7.        **this**.start = start;  
8.        **this**.end = end;  
9.     \}  
10.    //compute是RecursiveTask的主方法  
11.    **protected** **long** compute()\{  
12.       **long** max = Long.MIN\_VALUE;  
13.       **if**(end - start < RANG\_LENGTH)\{ //寻找最大值  
14.          **for**(**int** i = start; i<end;i++\{  
15.             **if**(array\[i\] > max)\{  
16.                max = array\[i\];  
17.             \}  
18.          \}  
19.       \}**else**\{ // 二分任务  
20.          **int** mid = (start + end) /2;  
21.          MaxValueTask lowTask = **new** MaxValueTask(array, start , mid);  
22.          MaxValueTask highTask = **new** MaxValueTask(array, mid, end);  
23.          lowTask.fork();// 异步启动任务  
24.          highTask.fork();  
25.          max = Math.max(max, lowTask.join());//等待执行结果  
26.          max = Math.max(max, highTask.join();  
27.       \}  
28.       **return** max;  
29.    \}  
30.    **public** Long calculate(**long**\[\] array)\{  
31.       MaxValueTask task = **new** MaxValueTask(array, 0 , array.length);  
32.       Long result = forkJoinPool.invoke(task);  
33.       **return** result;  
34.    \}  
35. \}

注：这个例子是示例，但从性能上说直接对整个数组顺序比较效率高，毕竟多线程所带来的额外开销过大。

在实际中，F/J框架发挥作用的场合很多，比如在一个目录包含的所有文本中搜索某个关键字，可以每个文件创建一个子任务。

如果相关的功能可以用递归和分治来解决，就适合F/J。

**2、多阶段线程同步工具**

Phaser类是Java SE 7中新增的一个使用同步工具，功能和灵活性比倒数闸门和循环屏障要强很多。

在F/J框架中的子任务之间要进行同步时，应优先考虑Phaser。

Phaser把多个线程写作执行的任务划分成多个阶段（phase），编程时要明确各个阶段的任务，每个阶段都可以有任意个参与者，线程可以随时注册并参与到某个阶段，当一个阶段中所有线程都成功完成之后，Phaser的onAdvance()被调用，可以通过覆盖添加自定义处理逻辑（类似循环屏障的使用的Runnable接口），然后Phaser类会自动进入下个阶段。如此循环，知道Phaser不再包含任何参与者。

Phaser创建后，初始阶段编号为0，构造函数中指定初始参与个数。

arrive()，某个参与者完成任务后调用

arriveAndDeregister()，任务完成，取消自己的注册。

arriveAndAwaitAdvance()，自己完成等待其他参与者完成。，进入阻塞，直到Phaser成功进入下个阶段。

awaitAdvance()、awaitAdvanceInterruptibly()，等待phaser进入下个阶段，参数为当前阶段的编号，后者可以设置超时和处理中断请求。

另外，Phaser的一个重要特征是多个Phaser可以组成树形结构，Phaser提供了构造方法来指定当前对象的父对象；当一个子对象参与者>0，会自动注册到父对象中；当=0，自动解除注册。

例：从指定网址，下载img标签的照片

阶段1、处理网址对应的html文本，和抽取img的链接；2、创建图片下载子线程，主线程等待；3、子线程下载图片，主线程等待；4、任务完成退出

**\[java\]**  [view plain][]   [copy][view plain]

[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** WebPageImageDownloader\{  
2.     **private** **final** Phaser phaser = **new** Phaser(1);//初始参与数1，代表主线程。  
3.     **public** **void** download(URL url, **final** Path path) **throws** IOException\{  
4.        String content = getContent(url);//获得HTML文本，省略。  
5.        List<URL> imageUrls = extractImageUrls(content);//获得图片链接，省略。  
6.        **for**(**final** URL imageUrl : imageUrls)\{  
7.           phaser.register();//子线程注册  
8.           **new** Thread()\{  
9.              **public** **void** run()\{  
10.                phaser.arriveAndAwaitAdvance();//第二阶段的等待，等待进入第三阶段  
11.                **try**\{  
12.                   InputStream is = imageUrl.openStream();  
13.                   File.copy(is, getSavePath(path, imageUrl), StandardCopyOption.REPLACE\_EXISTING);  
14.                \}**catch**(IOException e)\{  
15.                   e.printStackTrace():  
16.                \}**finally**\{  
17.                   phaser.arriveAndDeregister();//子线程完成任务，退出。  
18.                \}  
19.             \}  
20.         \}.start();  
21.       \}  
22.       phaser.arriveAndAwaitAdvance();//第二阶段等待，子线程在注册  
23.       phaser.arriveAndAwaitAdvance();//第三阶段等待，子线程在下载  
24.       phaser.arriveAndDeregister();//所有线程退出。  
25.    \}  
26. \}

**十一、ThreadLocal类**

java.lang.ThreadLocal，线程局部变量，把一个共享变量变为一个线程的私有对象。---复制--不同线程访问一个ThreadLocal类的对象时，锁访问和修改的事每个线程变量各自独立的对象。通过ThreadLocal可以快速把一个非线程安全的对象转换成线程安全的对象。（同时也就不能达到数据传递的作用了）。

a、get()和set()分别用来获取和设置当前线程中包含的对象的值。

b、remove()，删除。

c、initialValue()，初始化值。如果没有通过set方法设置值，第一个调用get，会通过initValue来获取对象的初始值。

ThreadLoacl的一般用法，创建一个ThreadLocal的匿名子类并覆盖initalValue()，把ThreadLoacl的使用封装在另一个类中

**\[java\]**  [view plain][]   [copy][view plain]

[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **class** ThreadLocalIdGenerator\{  
2.     **private** **static** **final** ThreadLocal<IdGenerator> idGenerator = **new** ThreadLocal<IdGenerator>()\{  
3.           **protected** IdGenerator initalValue()\{  
4.              **return** **new** IdGenerator();//IdGenerator 是个初始int value =0,然后getNext()\{  return value++\}  
5.           \}  
6.        \};  
7.     **public** **static** **int** getNext()\{  
8.        **return** idGenerator.get().getNext();  
9.     \}  
10. \}

ThreadLoal的另外一个作用是创建线程唯一的对象，在有些情况，一个对象在代码中各个部分都需要用到，传统做法是把这个对象作为参数在代码间传递，如果使用这个对I昂的代码都在同一个线程，可以封装在ThreadLocal中。

如：在多线程中，生成随机数

java.util.Random会带来竞争问题，**java.util.concurrent.ThreadLocalRandom类提供多线程下的随机数声场，底层是ThreadLoacl。**  
\-------------------------------------------------

Java并发编程：synchronized

虽然多线程编程极大地提高了效率，但是也会带来一定的隐患。比如说两个线程同时往一个数据库表中插入不重复的数据，就可能会导致数据库中插入了相同的数据。今天我们就来一起讨论下线程安全问题，以及Java中提供了什么机制来解决线程安全问题。

以下是本文的目录大纲：

一.什么时候会出现线程安全问题？

二.如何解决线程安全问题？

三.synchronized同步方法或者同步块

若有不正之处，请多多谅解并欢迎批评指正。

请尊重作者劳动成果，转载请标明原文链接：

http://www.cnblogs.com/dolphin0520/p/3923737.html

## 一.什么时候会出现线程安全问题？ ##

在单线程中不会出现线程安全问题，而在多线程编程中，有可能会出现同时访问同一个资源的情况，这种资源可以是各种类型的的资源：一个变量、一个对象、一个文件、一个数据库表等，而当多个线程同时访问同一个资源的时候，就会存在一个问题：

由于每个线程执行的过程是不可控的，所以很可能导致最终的结果与实际上的愿望相违背或者直接导致程序出错。

举个简单的例子：

现在有两个线程分别从网络上读取数据，然后插入一张数据库表中，要求不能插入重复的数据。

那么必然在插入数据的过程中存在两个操作：

1）检查数据库中是否存在该条数据；

2）如果存在，则不插入；如果不存在，则插入到数据库中。

假如两个线程分别用thread-1和thread-2表示，某一时刻，thread-1和thread-2都读取到了数据X，那么可能会发生这种情况：

thread-1去检查数据库中是否存在数据X，然后thread-2也接着去检查数据库中是否存在数据X。

结果两个线程检查的结果都是数据库中不存在数据X，那么两个线程都分别将数据X插入数据库表当中。

这个就是线程安全问题，即多个线程同时访问一个资源时，会导致程序运行结果并不是想看到的结果。

这里面，这个资源被称为：临界资源（也有称为共享资源）。

也就是说，当多个线程同时访问临界资源（一个对象，对象中的属性，一个文件，一个数据库等）时，就可能会产生线程安全问题。

不过，当多个线程执行一个方法，方法内部的局部变量并不是临界资源，因为方法是在栈上执行的，而Java栈是线程私有的，因此不会产生线程安全问题。

## 二.如何解决线程安全问题？ ##

那么一般来说，是如何解决线程安全问题的呢？

基本上所有的并发模式在解决线程安全问题时，都采用“序列化访问临界资源”的方案，即在同一时刻，只能有一个线程访问临界资源，也称作同步互斥访问。

通常来说，是在访问临界资源的代码前面加上一个锁，当访问完临界资源后释放锁，让其他线程继续访问。

在Java中，提供了两种方式来实现同步互斥访问：synchronized和Lock。

本文主要讲述synchronized的使用方法，Lock的使用方法在下一篇博文中讲述。

## 三.synchronized同步方法或者同步块 ##

在了解synchronized关键字的使用方法之前，我们先来看一个概念：互斥锁，顾名思义：能到达到互斥访问目的的锁。

举个简单的例子：如果对临界资源加上互斥锁，当一个线程在访问该临界资源时，其他线程便只能等待。

在Java中，每一个对象都拥有一个锁标记（monitor），也称为监视器，多线程同时访问某个对象时，线程只有获取了该对象的锁才能访问。

在Java中，可以使用synchronized关键字来标记一个方法或者代码块，当某个线程调用该对象的synchronized方法或者访问synchronized代码块时，这个线程便获得了该对象的锁，其他线程暂时无法访问这个方法，只有等待这个方法执行完毕或者代码块执行完毕，这个线程才会释放该对象的锁，其他线程才能执行这个方法或者代码块。

下面通过几个简单的例子来说明synchronized关键字的使用：

1.synchronized方法

下面这段代码中两个线程分别调用insertData对象插入数据：

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     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">static</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">main(String[] args)&nbsp; { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">final</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">InsertData insertData =&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">new</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">InsertData();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp; 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">new</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">Thread() { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">run() { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">insertData.insert(Thread.currentThread());</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">};</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}.start();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp; 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp; 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">new</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">Thread() { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">run() { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">insertData.insert(Thread.currentThread());</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">};</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}.start();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}&nbsp;&nbsp;</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
       &nbsp; 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">class</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">InsertData { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">private</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">ArrayList&lt;Integer&gt; arrayList =&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">new</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">ArrayList&lt;Integer&gt;();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp; 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">insert(Thread thread){ </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">for</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">(</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">int</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">i=</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,153,0)!important; background:none!important">0</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">;i&lt;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,153,0)!important; background:none!important">5</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">;i++){ </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">System.out.println(thread.getName()+</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:blue!important; background:none!important">"在插入数据"</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">+i);</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">arrayList.add(i);</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

此时程序的输出结果为：

![191740073939985.jpg][]

说明两个线程在同时执行insert方法。

而如果在insert方法前面加上关键字synchronized的话，运行结果为：

![191742096284061.jpg][]

从上输出结果说明，Thread-1插入数据是等Thread-0插入完数据之后才进行的。说明Thread-0和Thread-1是顺序执行insert方法的。

这就是synchronized方法。

不过有几点需要注意：

1）当一个线程正在访问一个对象的synchronized方法，那么其他线程不能访问该对象的其他synchronized方法。这个原因很简单，因为一个对象只有一把锁，当一个线程获取了该对象的锁之后，其他线程无法获取该对象的锁，所以无法访问该对象的其他synchronized方法。

2）当一个线程正在访问一个对象的synchronized方法，那么其他线程能访问该对象的非synchronized方法。这个原因很简单，访问非synchronized方法不需要获得该对象的锁，假如一个方法没用synchronized关键字修饰，说明它不会使用到临界资源，那么其他线程是可以访问这个方法的，

3）如果一个线程A需要访问对象object1的synchronized方法fun1，另外一个线程B需要访问对象object2的synchronized方法fun1，即使object1和object2是同一类型），也不会产生线程安全问题，因为他们访问的是不同的对象，所以不存在互斥问题。

2.synchronized代码块

synchronized代码块类似于以下这种形式：

当在某个线程中执行这段代码块，该线程会获取对象synObject的锁，从而使得其他线程无法同时访问该代码块。

synObject可以是this，代表获取当前对象的锁，也可以是类中的一个属性，代表获取该属性的锁。

比如上面的insert方法可以改成以下两种形式：

从上面可以看出，synchronized代码块使用起来比synchronized方法要灵活得多。因为也许一个方法中只有一部分代码只需要同步，如果此时对整个方法用synchronized进行同步，会影响程序执行效率。而使用synchronized代码块就可以避免这个问题，synchronized代码块可以实现只对需要同步的地方进行同步。

另外，每个类也会有一个锁，它可以用来控制对static数据成员的并发访问。

并且如果一个线程执行一个对象的非static synchronized方法，另外一个线程需要执行这个对象所属类的static synchronized方法，此时不会发生互斥现象，因为访问static synchronized方法占用的是类锁，而访问非static synchronized方法占用的是对象锁，所以不存在互斥现象。

看下面这段代码就明白了：

<table style="border-collapse:collapse; border-spacing:0px; border:1px solid silver; width:1256px; word-break:break-word; margin:0px!important; padding:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; font-size:12px!important; min-height:auto!important; background:none!important"> 
 <tbody style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
  <tr style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
   <td style="padding:3px; border:1px solid silver; border-collapse:collapse; margin:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:35px!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(175,175,175)!important; background:none!important"> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      1 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      2 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      3 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      4 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      5 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      6 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      7 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      8 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      9 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      10 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      11 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      12 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      13 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      14 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      15 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      16 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      17 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      18 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      19 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      20 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      21 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      22 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      23 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      24 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      25 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      26 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      27 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      28 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      29 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      30 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      31 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      32 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      33 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
      34 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em!important; border-width:0px 2px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
      35 
    </div> </td> 
   <td style="padding:3px; border:1px solid silver; border-collapse:collapse; margin:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important"> 
    <div style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:relative!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; background:none!important"> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">class</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">Test { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important">
       &nbsp; 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">static</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">main(String[] args)&nbsp; { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">final</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">InsertData insertData =&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">new</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">InsertData();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">new</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">Thread(){ </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:gray!important; background:none!important">@Override</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">run() { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">insertData.insert();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}.start();&nbsp;</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">new</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">Thread(){ </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:gray!important; background:none!important">@Override</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">run() { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">insertData.insert1();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}.start();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}&nbsp;&nbsp;</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important">
       &nbsp; 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">class</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">InsertData {&nbsp;</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">synchronized</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">insert(){ </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">System.out.println(</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:blue!important; background:none!important">"执行insert"</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">);</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">try</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">{ </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">Thread.sleep(</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,153,0)!important; background:none!important">5000</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">);</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">catch</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">(InterruptedException e) { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">e.printStackTrace();</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">System.out.println(</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:blue!important; background:none!important">"执行insert完毕"</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">);</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp; 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">public</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">synchronized</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">static</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important; background:none!important">void</code>&nbsp; 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">insert1() { </code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">System.out.println(</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:blue!important; background:none!important">"执行insert1"</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">);</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">System.out.println(</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:blue!important; background:none!important">"执行insert1完毕"</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">);</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; white-space:nowrap!important; background:none rgb(244,244,244)!important"> 
      <code style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; background:none!important">}</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

执行结果;

![192113596129599.jpg][]

**第一个线程里面执行的是insert方法，不会导致第二个线程执行insert1方法发生阻塞现象。**

下面我们看一下synchronized关键字到底做了什么事情，我们来反编译它的字节码看一下，下面这段代码反编译后的字节码为：

![192052201909119.jpg][]

从反编译获得的字节码可以看出，synchronized代码块实际上多了monitorenter和monitorexit两条指令。monitorenter指令执行时会让对象的**锁计数加1，**而monitorexit指令执行时会让对象的**锁计数减1，**其实这个与操作系统里面的PV操作很像，操作系统里面的PV操作就是用来控制多个线程对临界资源的访问。对于synchronized方法，执行中的线程识别该方法的 method\_info 结构是否有 ACC\_SYNCHRONIZED 标记设置，然后它自动获取对象的锁，调用方法，最后释放锁。如果有异常发生，线程自动释放锁。

有一点要注意：对于synchronized方法或者synchronized代码块，当出现异常时，JVM会自动释放当前线程占用的锁，因此不会由于异常导致出现死锁现象。

参考资料：

《Java编程思想》

[http://ifeve.com/synchronized-blocks/][http_ifeve.com_synchronized-blocks]

[http://ifeve.com/java-synchronized/][http_ifeve.com_java-synchronized]

[http://blog.csdn.net/ns\_code/article/details/17199201][http_blog.csdn.net_ns_code_article_details_17199201]

作者： [海子][Link 1]

出处： [http://www.cnblogs.com/dolphin0520/][Link 1]

本博客中未标明转载的文章归作者 [海子][Link 1]和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。

**总结：多线程开发中应该优先使用高层API，如果无法满足，使用java.util.concurrent.atomic和java.util.concurrent.locks包提供的中层API，而synchronized和volatile，以及wait,notify和notifyAll等低层API 应该最后考虑。**

[view plain]: http://blog.csdn.net/escaflone/article/details/10418651#
[CODE]: https://code.csdn.net/assets/CODE_ico.png
[CODE_CODE]: https://code.csdn.net/snippets/647151
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[20130828010551062]: /images/20220719/adb27bc6305846d8acaf16b4ba6a7314.png
[Java SE]: http://lib.csdn.net/base/12
[191740073939985.jpg]: /images/20220719/65c9ffaefb6a459785a329df073737ce.png
[191742096284061.jpg]: /images/20220719/dedd0cd0e59c465f84f01c8aad66fb0b.png
[192113596129599.jpg]: /images/20220719/8ea7adeec52d4da5a958adf8a03ac5c8.png
[192052201909119.jpg]: /images/20220719/67a5fcb504a24151a6476b57568b3f80.png
[http_ifeve.com_synchronized-blocks]: http://ifeve.com/synchronized-blocks/
[http_ifeve.com_java-synchronized]: http://ifeve.com/java-synchronized/
[http_blog.csdn.net_ns_code_article_details_17199201]: http://blog.csdn.net/ns_code/article/details/17199201
[Link 1]: http://www.cnblogs.com/dolphin0520/