线程抢答（2021-12-03）

  要求3个线程进行抢答，并返回抢答结果。

package ThreadDemo;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

class Responder implements Callable<String>{
    private boolean flag = true;    //规定true表示还能抢答，false表示抢答完成
    
    public String call(){
        synchronized (this) {
            if(flag==true) {
                this.flag = false;
                return Thread.currentThread().getName()+"  抢答成功！！！";
            }
            else {
                return Thread.currentThread().getName()+"  抢答失败。";
            }
        }
    }
}

public class Main {
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        Responder res = new Responder();
        FutureTask<String> taskA = new FutureTask<String>(res);
        FutureTask<String> taskB = new FutureTask<String>(res);
        FutureTask<String> taskC = new FutureTask<String>(res);
        new Thread(taskA,"抢答选手A").start();      
        new Thread(taskB,"抢答选手B").start();
        new Thread(taskC,"抢答选手C").start();      
        System.out.println(taskA.get());
        System.out.println(taskB.get());
        System.out.println(taskC.get());
    }
}