sleep和wait的应用

在面试中经常性的遇到wait和sleep的区别？

1.sleep不会释放锁，而wait会释放锁

    private static final String LOCK = "lock";public static void main(String[] args) {new Thread(() -> {System.out.println(Thread.currentThread().getName() + "====start");test();System.out.println(Thread.currentThread().getName() + "====end");}).start();new Thread(() -> {System.out.println(Thread.currentThread().getName() + "====start");test();System.out.println(Thread.currentThread().getName() + "=====end");}).start();}public static void test() {synchronized (LOCK) {System.out.println(Thread.currentThread().getName() + "====getLock" + System.currentTimeMillis());try {LOCK.wait(5000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName() + "====unLock" + +System.currentTimeMillis());}}Thread-0====start
Thread-0====getLock1603173719697
Thread-1====start
Thread-1====getLock1603173719697
Thread-1====unLock1603173724698
Thread-1=====end
Thread-0====unLock1603173724698
Thread-0====end

    private static final String LOCK = "lock";public static void main(String[] args) {new Thread(() -> {System.out.println(Thread.currentThread().getName() + "====start");test();System.out.println(Thread.currentThread().getName() + "====end");}).start();new Thread(() -> {System.out.println(Thread.currentThread().getName() + "====start");test();System.out.println(Thread.currentThread().getName() + "=====end");}).start();}public static void test() {synchronized (LOCK) {System.out.println(Thread.currentThread().getName() + "====getLock" + System.currentTimeMillis());try {Thread.sleep(4321L);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName() + "====unLock" + +System.currentTimeMillis());}}
Thread-0====start
Thread-1====start
Thread-1====getLock1603173961122
Thread-1====unLock1603173965444
Thread-1=====end
Thread-0====getLock1603173965444
Thread-0====unLock1603173969765
Thread-0====end

2.由上面的代码我们发现sleep方法是通过Thead的静态方法而wait是Object对象的方法

3.我们将同步块去掉会发现sleep方法会正常使用，而wait方法会出错（wait必须依赖同步块）

    public static void test() {System.out.println(Thread.currentThread().getName() + "====getLock" + System.currentTimeMillis());try {LOCK.wait(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName() + "====unLock" + +System.currentTimeMillis());}Thread-0====start
Thread-1====start
Thread-1====getLock1603174303023
Thread-0====getLock1603174303023
Exception in thread "Thread-1" Exception in thread "Thread-0" java.lang.IllegalMonitorStateExceptionat java.lang.Object.wait(Native Method)at com.zexiang.java.sync.reentrantsync.T.test(T.java:31)at com.zexiang.java.sync.reentrantsync.T.lambda$main$0(T.java:17)at java.lang.Thread.run(Thread.java:745)
java.lang.IllegalMonitorStateExceptionat java.lang.Object.wait(Native Method)at com.zexiang.java.sync.reentrantsync.T.test(T.java:31)at com.zexiang.java.sync.reentrantsync.T.lambda$main$1(T.java:22)at java.lang.Thread.run(Thread.java:745)

4.sleep必须设置时间而wait则可以都可以。如果不给时间参数必须要唤醒LOCK.notify();

                Thread.sleep(1000);LOCK.wait(1000);LOCK.wait();

sleep和wait的应用

在面试中经常性的遇到wait和sleep的区别？

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