完全数——多线程 (Java)

1. 代码

import java.util.Random;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class 线程完全数 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        ExecutorService exec = Executors.newCachedThreadPool(); // 线程池
        System.out.println("输入数据N(小于100000)：");
        int N = in.nextInt();
        int sum = 0;
        Divisor p[] = new Divisor[100000];
        for (int i = N-1; i > 0; i--) {
            p[i] = new Divisor(i,  N);
            exec.execute(p[i]); // start
        }
        exec.shutdown(); // 不在生成新的线程

        while(true) {
            if (exec.isTerminated()) { // 判断所有线程是否结束
                for (int i = 0; i < Global.index; i++) {
                    sum += Global.buffer[i];
                }
                System.out.println("------ 结果 -------");
                System.out.println("因子相加的结果：" + sum);
                if (sum == N) {
                    System.out.println(N + " 是完全数！");
                } else
                    System.out.println(N + " 不是完成数！");
                break;
            }
        }
    }
}
class Global{
    static int index = 0;
    static syn empty = new syn(3); // 信号量为3
    static int[] buffer = new int[10000]; // 公共缓冲区
}
class syn{
    int count = 1;
    syn(){}
    syn(int count){this.count = count;}
    public synchronized void Wait(){  // P操作
        count--;
        if(count < 0) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    public synchronized void Singnal(){ // V操作
        count++;
        if(count <= 0)
            this.notify();
    }
}
class Divisor extends Thread{
    public int divisor = 0, N;
    Divisor(int divisor, int N){
        this.divisor = divisor;
        this.N = N;
    }
    public void run(){
        Global.empty.Wait();
        // 临界区
        if(N % divisor == 0){
            System.out.println(divisor + " 是 " + N + " 的因子");
            Global.buffer[Global.index++] = divisor;
        }
//        try{
//            Thread.sleep(1); // 让效果明显一点，会慢
//        }catch (InterruptedException d){
//            d.printStackTrace();
//        }
        // 结束临界区
        Global.empty.Singnal();
    }
}

 

2. 结果：