Java并发-10.等待/通知

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.TimeUnit;

/**
 * @author pengjunzhe
 */
public class WaitNotify {
    static boolean flag = true;
    static Object lock = new Object();

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

    public static class Wait implements Runnable {
        @Override
        public void run() {
            // 加锁，获取lock对象的Monitor
            synchronized (lock) {
                // 条件不满足时，继续wait，同时释放lock的锁
                while (flag) {
                    try {
                        System.out.println(Thread.currentThread() + " flag is true. wait @ "
                                + new SimpleDateFormat("HH:mm:ss").format(new Date()));
                        lock.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                // 条件满足时，完成工作
                System.out.println(Thread.currentThread() + " flag is false. running @ " + new SimpleDateFormat("HH:mm:ss").format(new Date()));
            }
        }
    }

    public static class Notify implements Runnable {

        @Override
        public void run() {
            // 加锁，获取lock的Monitor
            synchronized (lock) {
                // 获取lock的锁，然后通知，通知时不释放lock的锁
                // 直到当前线程释放了lock之后，WaitThread才从wait方法返回
                System.out.println(Thread.currentThread() + " hold lock. notify @ " + new SimpleDateFormat("HH:mm:ss").format(new Date()));
                lock.notifyAll();
                flag = false;
                SleepUtils.second(5);
            }
            // 再次加锁
            synchronized (lock) {
                System.out.println(Thread.currentThread() + " hold lock again. sleep @ " + new SimpleDateFormat("HH:mm:ss").format(new Date()));
                SleepUtils.second(5);
            }
        }
    }
}

Thread[WaitThread,5,main] flag is true. wait @ 15:05:55
Thread[NotifyThread,5,main] hold lock. notify @ 15:05:56
Thread[NotifyThread,5,main] hold lock again. sleep @ 15:06:01
Thread[WaitThread,5,main] flag is false. running @ 15:06:06