jdk源码解析五之Thread 红太狼 2023-02-20 13:36 4阅读 0赞 ### 这里写自定义目录标题 ### * Thread * * 构造 * start * interrupt * join * State * run * 总结 * ThreadFactory * * DefaultThreadFactory # Thread # ## 构造 ## private void init(ThreadGroup g, Runnable target, String name, long stackSize, AccessControlContext acc, boolean inheritThreadLocals) { if (name == null) { throw new NullPointerException("name cannot be null"); } //线程名,默认"Thread-" + nextThreadNum() this.name = name; //获取当前线程 Thread parent = currentThread(); SecurityManager security = System.getSecurityManager(); //线程组为空 if (g == null) { /* Determine if it's an applet or not */ /* If there is a security manager, ask the security manager what to do. */ if (security != null) { g = security.getThreadGroup(); } /* If the security doesn't have a strong opinion of the matter use the parent thread group. */ if (g == null) { //默认继承父线程线程组 g = parent.getThreadGroup(); } } /* checkAccess regardless of whether or not threadgroup is explicitly passed in. */ g.checkAccess(); /* * Do we have the required permissions? */ if (security != null) { if (isCCLOverridden(getClass())) { security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION); } } g.addUnstarted(); this.group = g; //设置是否为守护线程,继承调用线程的主线程,main默认是false this.daemon = parent.isDaemon(); //默认5 this.priority = parent.getPriority(); if (security == null || isCCLOverridden(parent.getClass())) this.contextClassLoader = parent.getContextClassLoader(); else this.contextClassLoader = parent.contextClassLoader; this.inheritedAccessControlContext = acc != null ? acc : AccessController.getContext(); this.target = target; setPriority(priority); if (inheritThreadLocals && parent.inheritableThreadLocals != null) //创建线程共享变量副本 this.inheritableThreadLocals = ThreadLocal.createInheritedMap(parent.inheritableThreadLocals); /* Stash the specified stack size in case the VM cares */ //设置栈大小，如果未指定大小，将在jvm 初始化参数中声明：Xss参数进行指定*/ this.stackSize = stackSize; /* Set thread ID */ //设置线程id tid = nextThreadID(); } ## start ## public synchronized void start() { /** * This method is not invoked for the main method thread or "system" * group threads created/set up by the VM. Any new functionality added * to this method in the future may have to also be added to the VM. * * A zero status value corresponds to state "NEW". */ //当前线程状态 if (threadStatus != 0) throw new IllegalThreadStateException(); /* Notify the group that this thread is about to be started * so that it can be added to the group's list of threads * and the group's unstarted count can be decremented. */ //当前线程加入线程组 group.add(this); boolean started = false; try { //启动 start0(); //标记正常结束 started = true; } finally { try { if (!started) { //线程启动失败，从线程组里面移除该线程 group.threadStartFailed(this); } } catch (Throwable ignore) { /* do nothing. If start0 threw a Throwable then it will be passed up the call stack */ } } } ## interrupt ## public void interrupt() { //如果不是当前线程 if (this != Thread.currentThread()) //判断当前线程是否允许修改其他线程 checkAccess(); //中断 synchronized (blockerLock) { Interruptible b = blocker; if (b != null) { //设置中断标识位 interrupt0(); // Just to set the interrupt flag b.interrupt(this); return; } } interrupt0(); } ## join ## public final synchronized void join(long millis) throws InterruptedException { long base = System.currentTimeMillis(); long now = 0; if (millis < 0) { throw new IllegalArgumentException("timeout value is negative"); } //等待该线程终止的时间最长为 millis 毫秒。 if (millis == 0) { //测试线程是否处于活动状态。如果线程已经启动且尚未终止，则为活动状态。 while (isAlive()) { wait(0); } } else { //指定了超时时间 while (isAlive()) { long delay = millis - now; //超时,结束 if (delay <= 0) { break; } //等待阻塞 wait(delay); now = System.currentTimeMillis() - base; } } } ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70] ## State ## /* NEW：初始状态，线程被构建，还未调用start()方法； RUNNABLE：运行状态，在java多线程模型中，就绪和运行都是运行状态； BLOCKED：阻塞状态； WAITING：等待状态，比如中断，需要其他的线程来唤醒； TIME_WAITING：超时等待，可以在指定的时间内自行返回； TERMINATED：终止状态，线程执行完毕。*/ public enum State { } ## run ## public void run() { if (target != null) { target.run(); } } ## 总结 ## thread很多方法算是底层调用的了, 设置优先级调用,取决于操作系统 # ThreadFactory # ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 1] 基本上都是当做内部类使用,随便看一个实现即可 java.util.concurrent.Executors.DefaultThreadFactory ## DefaultThreadFactory ## static class DefaultThreadFactory implements ThreadFactory { private static final AtomicInteger poolNumber = new AtomicInteger(1); private final ThreadGroup group; private final AtomicInteger threadNumber = new AtomicInteger(1); private final String namePrefix; DefaultThreadFactory() { SecurityManager s = System.getSecurityManager(); //默认继承父类线程组 group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup(); //pool-自增1开始-thread- namePrefix = "pool-" + poolNumber.getAndIncrement() + "-thread-"; } public Thread newThread(Runnable r) { //pool-1-thread-1 Thread t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement(), 0); //是否是守护线程 if (t.isDaemon()) //如果是守护线程,则设置成普通线程 t.setDaemon(false); // //设置优先级,默认5 if (t.getPriority() != Thread.NORM_PRIORITY) t.setPriority(Thread.NORM_PRIORITY); return t; } } [watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200810131159996.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw==,size_16,color_FFFFFF,t_70 [watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200602192109685.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw==,size_16,color_FFFFFF,t_70
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