wait方法和notify方法的区别

1.wait()和sleep()的区别
wait()是Object类的方法，sleep()是Thread类的方法；
调用Object对象的wait方法，线程会放弃对象锁，进入等待此对象的等待锁定池；只有针对对象调用notify()方法后当前线程才进入对象锁定池准备获取对象锁进入运行状态，如果没有notify，对应的线程会挂起；
sleep()方法会让程序暂停执行指定的时间，让出CPU给其他线程，但是他的监控状态依然保持者，到达指定时间当前线程会自动恢复运行状态。在调用sleep()方法的过程中，线程不会释放对象锁。

2.实例Demo

public class ThreadWait extends Thread {
    @Override
    public void run() {
        synchronized (ThreadTest.class) {
            System.out.println("ThreadWait start...");
            System.out.println("ThreadWait waiting...");

            try {
                ThreadTest.class.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            System.out.println("ThreadWait continue...");

            System.out.println("ThreadWait end...");
        }
    }
}

public class ThreadSleep implements Runnable {
    @Override
    public void run() {
        synchronized (ThreadTest.class) {
            System.out.println("ThreadSleep start...");
            System.out.println("ThreadSleep sleeping");

            ThreadTest.class.notify();

            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            System.out.println("ThreadSleep continue...");

            System.out.println("ThreadSleep end...");
        }
    }
}

public class ThreadTest {
    public static void main(String[] args) {
        new ThreadWait().start();

        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(new ThreadSleep()).start();
    }
}

有该行代码ThreadTest.class.notify()的时候，输出结果：
ThreadWait start...
ThreadWait waiting...
ThreadSleep start...
ThreadSleep sleeping
ThreadSleep continue...
ThreadSleep end...
ThreadWait continue...
ThreadWait end...

没有该行代码ThreadTest.class.notify()的时候，输出结果：
ThreadWait start...
ThreadWait waiting...
ThreadSleep start...
ThreadSleep sleeping
ThreadSleep continue...
ThreadSleep end...