关于Java多线程遇到的问题.

1.最近在学习Java多线程,看到视频中要实现一个类似闹钟和小明的情景, 要求闹钟响,小明关闹钟, 三秒后闹钟再响,小明再关, 重复10次程序结束. 不知道为什么我的程序小明只能输出一次.

public class Test {
    public static void main(String[] args) {
        Clock ck = new Clock();
        new XiaoMing(ck);
    }
}


public class Clock implements Runnable{
    public Boolean isAlarm;
    public Boolean shutdown;

    public Clock() {
        isAlarm = false;
        shutdown = false;
        new Thread(this).start();
    }

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            isAlarm = true;
            System.out.println("Get up * 3 !");
            synchronized (this) {
                notifyAll();
                try {
                    wait(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
        shutdown = true;
    }
}


public class XiaoMing implements Runnable{
    private Clock clk;

    public XiaoMing(Clock clk) {
        this.clk = clk;
        new Thread(this).start();
    }

    @Override
    public void run() {
        while(true) {
            if (clk.isAlarm) {
                System.out.println("Woshixiaoming!");
                clk.isAlarm = false;
                synchronized (this) {
                    try {
                        wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
            else{
                if(clk.shutdown)    break;
            }
        }
    }
}

输出结果如下

Get up * 3 !
Woshixiaoming!
Get up * 3 !
Get up * 3 !
...(10 次 Getup, 之后程序停在那里)