Fork/Join 框架与传统线程池的区别采用“工作窃取”模式（work-stealing）：当执行新的任务时它可以将其拆分分成更小的任务执行，并将小任务加到线程队列中，然后再从一个随机线程的队列中偷一个并把它放在自己的队列中。

　　相对于一般的线程池实现,fork/join框架的优势体现在对其中包含的任务的处理方式上.在一般的线程池中,如果一个线程正在执行的任务由于某些原因无法继续运行,那么该线程会处于等待状态.而在fork/join框架实现中,如果某个子问题由于等待另外一个子问题的完成而无法继续运行.那么处理该子问题的线程会主动寻找其他尚未运行的子问题来执行.这种方式减少了线程的等待时间,提高了性能.

代码体验效果：

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();        }            }}
       

测试类：

import java.util.concurrent.ForkJoinPool;import java.util.concurrent.ForkJoinTask;import java.util.stream.LongStream;import org.junit.Test;public class TestForkJoin {    static long num = 10000000000000L;    @Test    public void test1(){        long start = System.currentTimeMillis();                ForkJoinPool pool = new ForkJoinPool();        ForkJoinTask
       
         task = new ForkJoinCalculate(0L, num);                long sum = pool.invoke(task);        System.out.println(sum);                long end = System.currentTimeMillis();                System.out.println("test1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 <= num; i++) {            sum += i;        }                System.out.println(sum);                long end = System.currentTimeMillis();                System.out.println("test2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, num)                             .parallel()                             .sum();                System.out.println(sum);                long end = System.currentTimeMillis();                System.out.println("test3耗费的时间为: " + (end - start)); //2061-2053-2086-18926    }}