等待/通知状态的变化

public class WaitNotify {

    static Object lock = new Object();

    static boolean flag = true;

    public static void main(String[] args) throws InterruptedException {
        Thread waitThread = new Thread(new Wait(), "WaitThread");
        waitThread.start();
        TimeUnit.SECONDS.sleep(1);
        Thread notifyThread = new Thread(new Notify(), "notifyThread");
        notifyThread.start();
    }

    static class Wait implements Runnable {
        @Override
        public void run() {
            synchronized (lock) {
                while (flag) {
                    System.out.println(Thread.currentThread() + "flag is true. wait@" + LocalDateTime.now());
                    try {
                        lock.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                System.out.println(Thread.currentThread() + "flag is false. running@" + LocalDateTime.now());
            }
        }
    }


    static class Notify implements Runnable {
        @Override
        public void run() {
            //加锁
            synchronized (lock){
                System.out.println(Thread.currentThread() + "hold lock. notify@" + LocalDateTime.now());
                //获取到lock锁之后，notifyAll，修改flag
                lock.notifyAll();
                flag = false;
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (lock){
                System.out.println(Thread.currentThread() + "hold lock. notify@" + LocalDateTime.now());
                try {
                    Thread.sleep(50000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

        }
    }
}

static class Notify implements Runnable {
    @Override
    public void run() {
        //加锁
        synchronized (lock){
            System.out.println(Thread.currentThread() + "hold lock. notify@" + LocalDateTime.now());
            //获取到lock锁之后，notifyAll，修改flag
            lock.notifyAll();
            flag = false;
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        synchronized (lock){
            System.out.println(Thread.currentThread() + "hold lock. notify@" + LocalDateTime.now());
            try {
                Thread.sleep(50000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }
}

}

WaitThread首先获得了对象的锁，然后调用对象的wait()方法，释放锁，进入了等待队列中，线程状态为waiting；NotifyThread获得了对象的锁，并调用对象的notify()方法，将WaitThread从等待队列移到同步队列中，此时WaitThread的状态变为阻塞Blocked，等待NotifyThread执行完之后释放锁之后WaitThread获取到锁之后0从wait()方法返回并继续执行。