public class MyService { private String lock = "123"; public void testMethod() { synchronized (lock) { System.out.println(ThreadB.currentThread().getName() + "begin " + System.currentTimeMillis()); lock="456"; try { ThreadB.sleep(2000); System.out.println(ThreadB.currentThread().getName() + "end " + System.currentTimeMillis()); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }
锁lock从“123” 改为“456”
ThreadA和ThreadB
public class ThreadA extends Thread { private MyService myService; public ThreadA(MyService myService) { this.myService = myService; } public void run() { myService.testMethod(); } } public class ThreadB extends Thread { private MyService myService; public ThreadB(MyService myService) { this.myService = myService; } public void run() { myService.testMethod(); } }
Run
public class Run { public static void main(String[] args) throws InterruptedException { MyService myService = new MyService(); ThreadA threadA= new ThreadA(myService); threadA.start(); Thread.sleep(50); ThreadA threadB= new ThreadA(myService); threadB.start(); } }
如果将Thread.sleep(50) 注释掉，A和B获取的锁都是“123”，虽然将锁改为“456”，结果还是同步的。
Java多线程（二） synchronized 锁对象的改变
原文：http://www.cnblogs.com/newlangwen/p/7596416.html
