ForkJoin

public class ForkJoinDemo extends RecursiveTask<Long> {

    private Long start;
    private Long end;
    private Long temp = 10000L;
    public ForkJoinDemo(Long start, Long end) {
        this.start = start;
        this.end = end;
    }


    /**
     * The main computation performed by this task.
     *
     * @return the result of the computation
     */
    @Override
    protected Long compute() {
        if ((end - start) < temp) {
            Long sum = 0L;
            for (Long i = start; i <= end; i++) {
                sum += i;
            }
            return sum;
        } else {
            long mid = (start + end) / 2;
            ForkJoinDemo task1 = new ForkJoinDemo(start, mid);
            task1.fork();
            ForkJoinDemo task2 = new ForkJoinDemo(mid + 1, end);
            task2.fork();
            return task1.join() + task2.join();
        }
    }
}

public static void test1() 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);
    Long sum = submit.get();
    long end = System.currentTimeMillis();
    System.out.println("sum = " + sum);
    System.out.println("耗时：" + (end - start));
}

sum = 500000000500000000
耗时：4950

public static void test2() {
    long start = System.currentTimeMillis();
    long sum = LongStream.rangeClosed(0L, 10_0000_0000L).parallel().reduce(0, Long::sum);
    long end = System.currentTimeMillis();
    System.out.println("sum = " + sum);
    System.out.println("耗时：" + (end - start));
}

sum = 500000000500000000
耗时：271