从头认识多线程-2.12 synchronized标记的方法和synchronized（this）标记的代码块锁定的是当前对象

这一章节我们来讨论一下synchronized标记的方法和synchronized（this）标记的代码块锁定的是当前对象。

1.其实从语句上面我们就已经可以看出synchronized(this)锁定的是当前对象，因为能够使用this的只有指代当前对象（当然，在构造器里面有些this除外）

2.代码清单：

package com.ray.deepintothread.ch02.topic_12;/** *  * @author RayLee * */public class ObjectLock2 {public static void main(String[] args) throws InterruptedException {MyService2 myService2 = new MyService2();ThreadThree threadThree = new ThreadThree(myService2);Thread thread = new Thread(threadThree);thread.start();ThreadFour threadFour = new ThreadFour(myService2);Thread thread2 = new Thread(threadFour);thread2.start();}}class ThreadThree implements Runnable {private MyService2 myService2;public ThreadThree(MyService2 myService2) {this.myService2 = myService2;}@Overridepublic void run() {try {myService2.updateA();} catch (InterruptedException e) {e.printStackTrace();}}}class ThreadFour implements Runnable {private MyService2 myService2;public ThreadFour(MyService2 myService2) {this.myService2 = myService2;}@Overridepublic void run() {try {myService2.updateB();} catch (InterruptedException e) {e.printStackTrace();}}}class MyService2 {private int count = 0;public synchronized void updateA() throws InterruptedException {System.out.println(this);for (int i = 0; i < 5; i++) {System.out.println("Thread name:" + Thread.currentThread().getName() + " count:" + count++);Thread.sleep(50);}}public synchronized void updateB() throws InterruptedException {System.out.println(this);for (int i = 0; i < 5; i++) {System.out.println("Thread name:" + Thread.currentThread().getName() + " count:" + count++);Thread.sleep(100);}}}

输出：

com.ray.deepintothread.ch02.topic_12.MyService2@9f34d54
Thread name:Thread-0 count:0
Thread name:Thread-0 count:1
Thread name:Thread-0 count:2
Thread name:Thread-0 count:3
Thread name:Thread-0 count:4
com.ray.deepintothread.ch02.topic_12.MyService2@9f34d54
Thread name:Thread-1 count:5
Thread name:Thread-1 count:6
Thread name:Thread-1 count:7
Thread name:Thread-1 count:8
Thread name:Thread-1 count:9

package com.ray.deepintothread.ch02.topic_12;/** *  * @author RayLee * */public class ObjectLock {public static void main(String[] args) throws InterruptedException {MyService myService = new MyService();ThreadOne threadOne = new ThreadOne(myService);Thread thread = new Thread(threadOne);thread.start();ThreadTwo threadTwo = new ThreadTwo(myService);Thread thread2 = new Thread(threadTwo);thread2.start();}}class ThreadOne implements Runnable {private MyService myService;public ThreadOne(MyService myService) {this.myService = myService;}@Overridepublic void run() {try {myService.updateA();} catch (InterruptedException e) {e.printStackTrace();}}}class ThreadTwo implements Runnable {private MyService myService;public ThreadTwo(MyService myService) {this.myService = myService;}@Overridepublic void run() {try {myService.updateB();} catch (InterruptedException e) {e.printStackTrace();}}}class MyService {public void updateA() throws InterruptedException {synchronized (this) {long startTime = System.currentTimeMillis();System.out.println("updateA startTime:" + startTime);Thread.sleep(1000);long endTime = System.currentTimeMillis();System.out.println("updateA endTime:" + endTime);}}public void updateB() throws InterruptedException {synchronized (this) {long startTime = System.currentTimeMillis();System.out.println("updateB startTime:" + startTime);Thread.sleep(1000);long endTime = System.currentTimeMillis();System.out.println("updateB endTime:" + endTime);}}}

2.结论

看第一个代码清单，synchronized标记的方法，我们其实比较难发现标记的是当前对象，只有在方法里面打印出来才知道，对比两个对象的内存地址，是一致的

看第二个代码清单，因为直接是引用this，因此肯定是当前对象

总结：这一章节展示了synchronized标记的方法和synchronized（this）标记的代码块锁定的是当前对象。

这一章节就到这里，谢谢

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我的github：https://github.com/raylee2015/DeepIntoThread

目录：http://blog.csdn.net/raylee2007/article/details/51204573