Java并发编程之Fork/Join框架的理解

package com.xz.thread.ForkJoin;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.concurrent.RecursiveTask;

/**
 * @description:
 * @author: xz
 * @create: 2021-06-06 17:15
 */
public class Demo extends RecursiveTask<Integer> {
    private int start;//子任务开始计算的开始值
    private int end;//子任务开始计算的结束值

    private static final Integer MAX_VALUE = 50;

    //构造方法
    public Demo(int start, int end) {
        this.start = start;
        this.end = end;
    }

    //计算
    @Override
    protected Integer compute() {
        int sum =0;
        //如果所需要计算的数值拆分为足够小，则进行累加计算
        if(end-start <= MAX_VALUE){
            System.out.println("startValue = " + start + ";endValue = " + end);
            for(int i=start;i<=end;i++){
                sum +=i;
            }
        }else{//否则再进行任务拆分,拆分成2个子任务
            Demo d1 = new Demo(start, (start + end) / 2);
            Demo d2 = new Demo((start + end) / 2, end);
            //执行2个子任务
            d1.fork();
            d2.fork();
            //合并子任务
            Integer value1= d1.join();
            Integer value2= d2.join();
            sum =value1+value2;
        }

        return sum;
    }

    //测试
    public static void main(String[] args) throws Exception{
        //ForkJoinPool主要用于实现“分而治之”的算法，特别是分治之后递归调用的函数
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        //提交一个ForkJoinTask执行
        ForkJoinTask<Integer> forkJoinTask = forkJoinPool.submit(new Demo(1,200));
        System.out.println("计算结果="+forkJoinTask.get());
    }
}