public class CountTask extends RecursiveTask<Integer> { 
    private static final int THRESHOLD = 2;// 阈值 
    private int start; 
    private int end; 
    public CountTask(int start, int end) { 
        this.start = start; 
        this.end = end; 
    } 
    protected Integer compute() { 
        int sum = 0; 
// 如果任务足够小就计算任务 
        boolean canCompute = (end - start) <= THRESHOLD; 
        if (canCompute) { 
            for (int i = start; i <= end; i++) { 
                sum += i; 
            } 
        } else { 
// 如果任务大于阈值，就分裂成两个子任务计算 
            int middle = (start + end) / 2; 
            CountTask leftTask = new CountTask(start, middle); 
            CountTask rightTask = new CountTask(middle + 1, end); 
// 执行子任务 
            leftTask.fork(); 
            rightTask.fork(); 
// 等待子任务执行完，并得到其结果 
            int leftResult=leftTask.join(); 
            int rightResult=rightTask.join(); 
// 合并子任务 
            sum = leftResult + rightResult; 
        } 
        return sum; 
    } 
    static public  void test(){ 
        ForkJoinPool forkJoinPool = new ForkJoinPool(); 
// 生成一个计算任务，负责计算1+2+3+4 
        CountTask task = new CountTask(1, 40000); 
// 执行一个任务 
        Future<Integer> result = forkJoinPool.submit(task); 
        try { 
            System.out.println(result.get()); 
        } catch (InterruptedException e) { 
        } catch (ExecutionException e) { 
        } 
    } 
}