ForkJoin学习

package com.king.forkjoin;

import java.util.concurrent.RecursiveAction;
import java.util.concurrent.RecursiveTask;

/**
 *  求和计算任务
 *  3000 6000(ForkJoin) 9000(Stream并行流)
 *  //1.如何使用forkJoinPool  通过它来执行
 *  //2.计算任务forkJoinPool.execute(ForkJoinTask task)
 *  //3.计算类要继承ForkJoinTask
 */

public class ForkJoinDemo extends RecursiveTask<Long> {
    private Long start;
    private Long end;
    private Long temp = 10000L;

    public ForkJoinDemo(Long start, Long end) {
        this.start = start;
        this.end = end;
    }

    //计算方法
    @Override
    protected Long compute() {
        if ((end-start)<temp){
            Long sum = 0L;
            for (Long i = start; i < end; i++) {
                sum+=i;
            }
            return sum;
        }else { //forkJoin
            long middle = (start + end) / 2;    //中间值
            ForkJoinDemo task1 = new ForkJoinDemo(start, middle);
            task1.fork();//拆分任务,把任务压入线程队列
            ForkJoinDemo task2 = new ForkJoinDemo(middle+1, end);
            task2.fork();//拆分任务,把任务压入线程队列
            return task1.join() + task2.join();
        }
    }
}

package com.king.forkjoin;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.stream.LongStream;


/*
* 同一任务，效率更高
* */
public class Test {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        test3();
    }

    //普通方法
    public static void test1(){
        Long sum = 0L;
        long start = System.currentTimeMillis();
        for (Long i = 1L; i < 10_0000_0000; i++) {
            sum+=i;
        }
        long end = System.currentTimeMillis();
        System.out.println("sum="+sum+"时间:"+(end-start));
    }

    //ForkJoin方法
    public static void test2() throws ExecutionException, InterruptedException {
        long start = System.currentTimeMillis();
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        ForkJoinTask<Long> task = new ForkJoinDemo(0L, 10_0000_0000L);
        forkJoinPool.execute(task); //执行
        ForkJoinTask<Long> submit = forkJoinPool.submit(task);//提交
        Long sum = submit.get();

        long end = System.currentTimeMillis();
        System.out.println("sum="+sum+"时间:"+(end-start));
    }
    public static void test3(){
        long start = System.currentTimeMillis();
        //Stream并行流
        long sum = LongStream.rangeClosed(0L, 10_0000_0000L).parallel().reduce(0, Long::sum);
        long end = System.currentTimeMillis();
        System.out.println("sum="+sum+"时间:"+(end-start));
    }
}