Fork-join框架

forkjoin特点：工作密取，平衡可用线程的工作负载。分支并行

每个工作线程都有一个双端队列 （一个工作线程将子任务压入其双端队列队头，一个工作线程空闲时，它会从另一个双端队列的队尾“密取”一个任务）

主要用于大数据下的计算

package com.wfy.ForkJoin;
import java.util.concurrent.RecursiveTask;
//求和计算
public class ForkJoinDemo extends RecursiveTask<Long> {
    private Long start;
    private Long end;


    public ForkJoinDemo(long start, long end) {
        this.start = start;
        this.end = end;
    }
    //分支计算方法
    @Override
    protected Long compute() {
        Long temp = 10000L;
        if ((end - start) < temp) {
            Long num = 0L;
            for (Long i = start; i < end; i++) {
                num += i;
            }
            return num;
        } else {
            //forkjoin
            long middle = (end - start) / 2;
            ForkJoinDemo task1 = new ForkJoinDemo(start, middle);
            task1.fork();//拆分任务，将任务压入线程
            ForkJoinDemo task2 = new ForkJoinDemo(middle + 1, end);
            task2.fork();//拆分任务，将任务压入线程
            return  task1.join()+ task2.join();
        }
    }
}

测试方法

package com.wfy.ForkJoin;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.stream.LongStream;

//线程求和计算的耗时比较
public class Test {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        //普通方法
       // test01();
        //forkjoin方法
        //test02();
        test03();
    }
    //普通方法
    public static  void test01(){
        Long sum=0L;
        long start = System.currentTimeMillis();
        for (int i = 0; i <=10_0000_0000 ; i++) {
                     sum+=i;
        }
        long end=  System.currentTimeMillis();
        System.out.println("sum= "+sum+"\t"+"时间="+(end-start));
    }
    //forkJoin方法
    public static  void test02() throws ExecutionException, InterruptedException {
        long start = System.currentTimeMillis();
        ForkJoinPool forkJoinPool = new ForkJoinPool();
       ForkJoinTask<Long> task = new ForkJoinDemo(0L,10_0000_0000L);
        ForkJoinTask<Long> submit = forkJoinPool.submit(task);//提交任务
        Long sum = submit.get();
        long end=  System.currentTimeMillis();
        System.out.println("sum= "+sum+"\t"+"时间="+(end-start));
    }

     //Stream并行流
    public static void test03(){
        long start = System.currentTimeMillis();
        long sum = LongStream.rangeClosed(0, 10_0000_0000).parallel().reduce(0, Long::sum);
        long end=  System.currentTimeMillis();
        System.out.println("sum= "+sum+"\t"+"时间="+(end-start));
    }
}