1、Java8中forkjoin框架使用更加简单了

1.7中的ForkJoin框架编码复杂且容易出错，而8中的编码则十分简单

JDK1.7时开发者需要自定义计算类，如

package com.atguigu.java8;

import java.util.concurrent.RecursiveTask;

public class ForkJoinCalculate extends RecursiveTask{

/**

*

*/

private static final long serialVersionUID = 13475679780L;

private long start;

private long end;

private static final long THRESHOLD = 10000L; //临界值

public ForkJoinCalculate(long start, long end) {

this.start = start;

this.end = end;

}

@Override

protected Long compute() {

long length = end - start;

if(length <= THRESHOLD){

long sum = 0;

for (long i = start; i <= end; i++) {

sum += i;

}

return sum;

}else{

long middle = (start + end) / 2;

ForkJoinCalculate left = new ForkJoinCalculate(start, middle);

left.fork(); //拆分，并将该子任务压入线程队列

ForkJoinCalculate right = new ForkJoinCalculate(middle+1, end);

right.fork();

return left.join() + right.join();

}

}

}

J8示例

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 {

@Test

public void test1(){

long start = System.currentTimeMillis();

ForkJoinPool pool = new ForkJoinPool();

ForkJoinTask 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

}

@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

}

@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

}

}