Sleep和Wait的区别

基本区别：

1、 sleep()来自Thread， wait() 来自Object
2、sleep可以在任何地方使用
wait只能在synchronized方法或者synchronized块中使用 （因为wait会释放锁，所有只有获取了锁，才会释放锁）

最主要的本质区别
Thrad.sleep只会让出CPU，不会导致锁行为的改变
Object.wait不仅让出CPU，还会释放已经占有的同步锁资源

public class WaitSleepDemo {

    public static void main(String[] args) {
        final  Object lock = new Object();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("thread A is waiting to get lock");
                synchronized (lock){

                    try {
                        System.out.println("thread A get lock");
                        Thread.sleep(20);
                        System.out.println("thread A do wait method");
                        lock.wait(1000);
                        System.out.println("thread A is done");


                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }
            }
        }).start();


        //为了让Thread A 先于Thread B执行
        try {
            Thread.sleep(10);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("thread B is waiting to get lock");
                synchronized (lock){

                    try {
                        System.out.println("thread B get lock");
                        System.out.println("thread B is sleeping 10 ms");
                        Thread.sleep(10);
                        System.out.println("thread B is done");


                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }
            }
        }).start();
    }
}

　　执行结果：

thread A is waiting to get lock
thread A get lock
thread B is waiting to get lock
thread A do wait method
thread B get lock
thread B is sleeping 10 ms
thread B is done
thread A is done

　　上面的代码验证了： Object.wait不仅让出CPU，还会释放已经占有的同步锁资源 

 

调整后的代码

public class WaitSleepDemo {

    public static void main(String[] args) {
        final  Object lock = new Object();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("thread A is waiting to get lock");
                synchronized (lock){

                    try {
                        System.out.println("thread A get lock");
                        Thread.sleep(20);
                        System.out.println("thread A do wait method");
                        //lock.wait(1000);
                        Thread.sleep(1000);
                        System.out.println("thread A is done");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();


        //为了让Thread A 先于Thread B执行
        try {
            Thread.sleep(10);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("thread B is waiting to get lock");
                synchronized (lock){
                    try {
                        System.out.println("thread B get lock");
                        System.out.println("thread B is sleeping 10 ms");
                       // Thread.sleep(10);
                        lock.wait(10);
                        System.out.println("thread B is done");


                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }
            }
        }).start();
    }
}

　　打印结果：

thread A is waiting to get lock
thread A get lock
thread B is waiting to get lock
thread A do wait method
thread A is done
thread B get lock
thread B is sleeping 10 ms
thread B is done

　　上面的代码验证了：Thrad.sleep只会让出CPU，不会导致锁行为的改变