我们先来看一下实例代码：

class ThreadA extends Thread{ public ThreadA(String name) { super(name); } public void run() { synchronized (this) { System.out.println(Thread.currentThread().getName()+" call notify()"); notify(); } }}public class WaitTest { public static void main(String[] args) { ThreadA t1 = new ThreadA("t1"); synchronized(t1) { try { // 启动“线程t1” System.out.println(Thread.currentThread().getName()+" start t1"); t1.start(); // 主线程等待t1通过notify()唤醒。 System.out.println(Thread.currentThread().getName()+" wait()"); t1.wait(); System.out.println(Thread.currentThread().getName()+" continue"); } catch (InterruptedException e) { e.printStackTrace(); } } }}

输出结果：main start t1 -> main wait() -> t1 call notify() -> main continue

其实调用t1.start()，t1为就绪状态，只是main方法中，t1被main线程锁住了，t1.wait()的时候，让当前线程等待，其实是让main线程等待了，然后释放了t1锁，t1线程执行，打印t1 call notify()，然后唤醒main线程，最后结束；

这里说一下wait()与sleep()的区别，他们的共同点都是让线程休眠，但是wait()会释放对象同步锁，而sleep()不会；下面的代码t1结束之后才会运行t2；能够证实这一点；

public class SleepLockTest{ private static Object obj = new Object(); public static void main(String[] args){ ThreadA t1 = new ThreadA("t1"); ThreadA t2 = new ThreadA("t2"); t1.start(); t2.start(); } static class ThreadA extends Thread{ public ThreadA(String name){ super(name); } public void run(){ synchronized (obj) { try { for(int i=0; i <10; i++){ System.out.printf("%s: %d\n", this.getName(), i); // i能被4整除时，休眠100毫秒 if (i%4 == 0) Thread.sleep(100); } } catch (InterruptedException e) { e.printStackTrace(); } } } } }