sleep和wait的应用

最新推荐文章于 2023-03-14 09:10:04 发布

原创最新推荐文章于 2023-03-14 09:10:04 发布 · 540 阅读

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本文详细解析了Java中wait与sleep方法的区别，包括锁的行为、使用方式、等待时间等关键特性，并通过示例代码直观展示了两者的不同之处。

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.IllegalMonitorStateException
	at 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$0(T.java:17)
	at java.lang.Thread.run(Thread.java:745)
java.lang.IllegalMonitorStateException
	at java.lang.Object.wait(Native Method)
	at com.zexiang.java.sync.reentrantsync.T.test(T.java:31)
	at com.zexiang.java.sync.reentrantsync.T.lambda$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();