ForkJoin示例

package com.atguigu.juc;

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

import org.junit.Test;

public class TestForkJoinPool {

public static void main(String[] args) {
	long start = System.currentTimeMillis();
	
	ForkJoinPool pool = new ForkJoinPool();
	
	ForkJoinTask task = new ForkJoinSum(0L, 30000000000L);
	
	long sum = pool.invoke(task);
	
	System.out.println(sum);
	
	long end = System.currentTimeMillis();
	
	System.out.println("耗费时间为：" + (end - start)); //291 4656
}

@Test
public void test1(){
	long start = System.currentTimeMillis();
	
	long sum = 0L;
	
	for (long i = 0; i <= 30000000000L; i++) {
		sum += i;
	}
	
	System.out.println(sum);
	
	long end = System.currentTimeMillis();
	
	System.out.println("耗费时间为：" + (end - start));//69 3966
}

}

class ForkJoinSum extends RecursiveTask{

/**
 * 
 */
private static final long serialVersionUID = -1257568709792496086L;

private long start;
private long end;

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

public ForkJoinSum(long start, long end){
	this.start = start;
	this.end = end;
}

@Override
protected Long compute() {
	long length = end - start;
	
	if(length <= THRESHOLD){
		long sum = 0L;
		
		for (long i = start; i <= end; i++) {
			sum += i;
		}
		
		return sum;
	}else{
		long middle = (start + end) / 2;
		ForkJoinSum left = new ForkJoinSum(start, middle);
		left.fork();
		
		ForkJoinSum right = new ForkJoinSum(middle + 1, end);
		right.fork();
		
		return left.join() + right.join();
	}
}

}