静态同步synchronized方法与synchronized(class)代码块（菜鸟玩线程）

太过爱你忘了你带给我的痛 2024-02-19 13:09 13阅读 0赞

## 静态同步synchronized方法与synchronized(class)代码块 ##

### 理论 ###

*  `synchronized还可以应用在static静态方法上，如果这样写，那是对当前的*.java文件对应的Class类进行持锁。`
 *  `synchronized关键字加到static静态方法上是给Class类上锁，而synchronized关键字加到非static静态方法上是给对象上锁。`
 *  `一个是对象锁，另外一个是Class锁，而Class锁可以对类的所有对象实例起作用。`
 *  `同步synchronized(class)代码块的作用其实和synchronized static方法的作用是一样的。`

### 落地 ###

##### 自定义共享变量类 #####

package com.chapter02.thread2_2_9_1;
    
    public class Service {
        
    /*    synchronized public static void printA() {
            try {
                System.out.println("THREAD NAME = " + Thread.currentThread().getName() + ", AT " + System.currentTimeMillis() + " ENTER printA");
                Thread.sleep(3000);
                System.out.println("THREAD NAME = " + Thread.currentThread().getName() + ", AT " + System.currentTimeMillis() + " OUT printA");
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
    
        synchronized public static void printB() {
            System.out.println("THREAD NAME = " + Thread.currentThread().getName() + ", AT " + System.currentTimeMillis() + " ENTER printB");
            System.out.println("THREAD NAME = " + Thread.currentThread().getName() + ", AT " + System.currentTimeMillis() + " OUT printB");
        }*/
    
        public static void printA() {
        
            synchronized (Service.class) {
        
                try {
        
                    System.out.println("THREAD NAME = " + Thread.currentThread().getName() + ", AT " + System.currentTimeMillis() + " ENTER printA");
                    Thread.sleep(3000);
                    System.out.println("THREAD NAME = " + Thread.currentThread().getName() + ", AT " + System.currentTimeMillis() + " OUT printA");
                } catch (Exception ex) {
        
                    ex.printStackTrace();
                }
            }
        }
    
        public static void printB() {
        
            synchronized (Service.class) {
        
                System.out.println("THREAD NAME = " + Thread.currentThread().getName() + ", AT " + System.currentTimeMillis() + " ENTER printB");
                System.out.println("THREAD NAME = " + Thread.currentThread().getName() + ", AT " + System.currentTimeMillis() + " OUT printB");
            }
        }
    }

##### 自定义线程1 #####

package com.chapter02.thread2_2_9_1;
    
    public class ThreadA extends Thread {
        
        private Service service;
    
        public ThreadA(Service service) {
        
            this.service = service;
        }
    
        @Override
        public void run() {
        
            super.run();
            service.printA();
        }
    }

##### 自定义线程2 #####

package com.chapter02.thread2_2_9_1;
    
    public class ThreadB extends Thread {
        
        private Service service;
    
        public ThreadB(Service service) {
        
            this.service = service;
        }
    
        @Override
        public void run() {
        
            super.run();
            service.printB();
        }
    }

##### 启动类 #####

package com.chapter02.thread2_2_9_1;
    
    public class Run {
        
        public static void main(String[] args) {
        
            Service service1 = new Service();
            Service service2 = new Service();
    
            ThreadA threadA = new ThreadA(service1);
            threadA.setName("A");
            threadA.start();
    
            ThreadB threadB = new ThreadB(service2);
            threadB.setName("B");
            threadB.start();
        }
    }

##### 执行结果 #####

THREAD NAME = A, AT 1541658444300 ENTER printA
    THREAD NAME = A, AT 1541658447301 OUT printA
    THREAD NAME = B, AT 1541658447302 ENTER printB
    THREAD NAME = B, AT 1541658447302 OUT printB