线程等待和唤醒的方法(三)

学习LockSupport类中通过part()和unpart()方法来实现阻塞和唤醒线程

1、使用part()和unpart()线程等待和唤醒情况，且无锁块要求

public static void main(String[] args) {
        Thread parkThread = new Thread(() -> {
            System.out.println(Thread.currentThread().getName() + "t" + "parkThread come in");
            LockSupport.park();
            System.out.println(Thread.currentThread().getName() + "t" + "parkThread out");
        }, "parkThread");
        parkThread.start();

        try{TimeUnit.SECONDS.sleep(3);} catch (InterruptedException e) {e.printStackTrace();} // 延迟3秒

        Thread unparkThread = new Thread(() -> {
            LockSupport.unpark(parkThread);
            System.out.println(Thread.currentThread().getName() + "t" + "unparkThread unpark");
        }, "unparkThread");
        unparkThread.start();

    }

 运行结果：parkThread    parkThread come in
                   unparkThread    unparkThread unpark
                   parkThread    parkThread out

 2、尝试先执行unpart()方法, 后执行part()方法来唤醒线程

public static void main(String[] args) {
        Thread parkThread = new Thread(() -> {
            System.out.println(Thread.currentThread().getName() + "t" + "parkThread come in");
            try{TimeUnit.SECONDS.sleep(3);} catch (InterruptedException e) {e.printStackTrace();} // 延迟3秒
            LockSupport.park();
            System.out.println(Thread.currentThread().getName() + "t" + "parkThread out");
        }, "parkThread");
        parkThread.start();

        Thread unparkThread = new Thread(() -> {
            LockSupport.unpark(parkThread);
            System.out.println(Thread.currentThread().getName() + "t" + "unparkThread unpark");
        }, "unparkThread");
        unparkThread.start();

    }

 运行结果：parkThread    parkThread come in
                   unparkThread    unparkThread unpark
                   parkThread    parkThread out

 总结：可以看出，LockSupport线程等待和唤醒没有wait()和notify方法那样的同步代码块，也没有像await()和singnal()方法那样的锁块，也能够正常运行，且不受顺序的影响。LockSupport在AQS中运用较多，有兴趣的同学可以看看源码。