从头认识多线程-2.10 通过同步代码块证明synchronized标记的是对象锁

这一章节我们来讨论一下通过同步代码块证明synchronized标记的是对象锁。

1.代码清单：

package com.ray.deepintothread.ch02.topic_11;

/**
 * 
 * @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;
	}

	@Override
	public void run() {
		try {
			myService.updateA();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}

class ThreadTwo implements Runnable {

	private MyService myService;

	public ThreadTwo(MyService myService) {
		this.myService = myService;
	}

	@Override
	public 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);
		}
	}

}

输出：

updateA startTime:1462281771917
updateA endTime:1462281772917
updateB startTime:1462281772917
updateB endTime:1462281773917

从上面的输出我们可以看出，两个线程同时执行，但是执行updateB的开始时间确实updateA的结束时间

换一个更加明显的例子：

输出：

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
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

从上面的输出我们可以看见，两个线程的执行是有先后顺序，只有等另一个执行完了，才执行下一个

2.结论：synchronized标记的是对象锁

总结：这一章节我们通过同步代码块证明synchronized标记的是对象锁。

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