java multithreading - lights Act

With flag

public class light {
public static void main(String[]args)
{
    Tv tv=new Tv();
    new Player(tv).start();
    new Watcher(tv).start();
}

}
//生产者 演员
class Player extends Thread{
Tv tv;
public Player(Tv tv)
{
    this.tv=tv;
}
public void run()
{
    for(int i=0;i<20;i++)
    {
        if(i%2==0)
        {
            this.tv.play("偶不变");
        }else
        {
            this.tv.play("奇变");
        }
    }
}
}
//消费者 观众
class Watcher extends Thread{
Tv tv;
public Watcher(Tv tv)
{
    this.tv=tv;
}
public void run()
{
    for(int i=0;i<20;i++)
    {
        this.tv.watch("无聊");
    }
}
}
//同一个资源 电视
    class Tv {

String voice;
//信号灯
//为真则演员表演，观众等待
//为假则观众观看，演员等待

boolean flag=true;

//表演
public synchronized void play(String voice)
{
    if(!flag)
    {
        try {
            this.wait();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    System.out.println("表演了:"+voice);
    this.voice=voice;

    //表演后
    this.notifyAll();
    this.flag=!this.flag;
}

public void watch(String string) {
    // TODO Auto-generated method stub

}

//观看
public synchronized void watch()
{
    if(flag)
    {
        try {
            this.wait();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    System.out.println("听到了:"+voice);

    //观看后:
    this.notifyAll();
    this.flag=!this.flag;
}
}