jdk8--stream并行流

stream的并行流要理解一个框架如下:

单线程,多线程和并行流对比

package com.atguigu.java8;

import java.util.concurrent.ForkJoinPool;

import java.util.concurrent.ForkJoinTask;

import java.util.stream.LongStream;

import org.junit.Test;

public class TestForkJoin {

    //线程池

    @Test

    public void test1(){

        long start = System.currentTimeMillis();

        ForkJoinPool pool = new ForkJoinPool();

        ForkJoinTask<Long> task = new ForkJoinCalculate(0L, 10000000000L);

        long sum = pool.invoke(task);

        System.out.println(sum);

        long end = System.currentTimeMillis();

        System.out.println("耗费的时间为: " + (end - start)); //112-1953-1988-2654-2647-20663-113808

    }

    //单线程

    @Test

    public void test2(){

        long start = System.currentTimeMillis();

        long sum = 0L;

        for (long i = 0L; i <= 10000000000L; i++) {

            sum += i;

        }

        System.out.println(sum);

        long end = System.currentTimeMillis();

        System.out.println("耗费的时间为: " + (end - start)); //34-3174-3132-4227-4223-31583

    }

    //并行流

    @Test

    public void test3(){

        long start = System.currentTimeMillis();

        Long sum = LongStream.rangeClosed(0L, 10000000000L)

                             .parallel()

                             .sum();

        System.out.println(sum);

        long end = System.currentTimeMillis();

        System.out.println("耗费的时间为: " + (end - start)); //2061-2053-2086-18926

    }

}