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运用多线程的信号灯法进行边加边计算！代码如下

public class JieChen {
    public static void main(String args[]){
        Sum sum = new Sum();
        new Play(sum).start();
        new Add(sum).start();

    }
}
class Play extends Thread{
    Sum sum;
    public Play(Sum sum){
        this.sum=sum;
    }

    @Override
    public void run() {
        for (int i = 1; i <= 20; i++) {
            this.sum.s*=i;
            this.sum.count++;
            this.sum.play(sum.voe);
        }
    }
}
class Add extends Thread{
    Sum sum;
    public Add(Sum sum){
        this.sum=sum;
    }

    @Override
    public void run() {
        for (int i = 1; i <= 20; i++) {
            sum.add();
            this.sum.sa+=this.sum.s;
        }
    }
}
class Sum{
    int s=1;
    int count=0;
    long sa=1;
    String voe;
    boolean flag = true;

    public synchronized void play(String voe){
        if(!flag){
            try{
                this.wait();
            }catch (InterruptedException e){
                e.printStackTrace();
            }
        }
        System.out.println("计算阶乘"+count+"!");
        this.notifyAll();
        this.voe=voe;
        this.flag=!this.flag;
    }
    public synchronized void add(){
        if(flag){
            try{
                this.wait();
            }catch (InterruptedException e){
                e.printStackTrace();
            }
        }
        System.out.println("加上阶乘结果为"+sa);
        this.notifyAll();
        this.flag=!this.flag;
    }
}

运行结果图