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();
}
}
}
}
}
