1 import java.util.concurrent.ExecutionException;
 2 import java.util.concurrent.ForkJoinPool;
 3 import java.util.concurrent.ForkJoinTask;
 4 import java.util.concurrent.RecursiveTask;
 5 
 6 /**
 7  *    并发执行任务
 8  */
 9 public class CountTask extends RecursiveTask<Integer> {
10 
11     private static final long serialVersionUID = 1L;
12     private static final int THRESHOLD = 2; //阈值
13     private int start;
14     private int end;
15     
16     public CountTask(int start,int end) {
17         this.start = start;
18         this.end = end;
19     }
20     
21     @Override
22     protected Integer compute() {
23         int sum = 0;
24         //如果任务足够小就计算任务
25         boolean canCompute = (end - start) <= THRESHOLD;
26         if(canCompute) {
27             for (int i = start; i <= end; i++) {
28                 sum += i;
29             }
30         }else {
31             //如果任务大于阈值 就分裂成两个子任务计算
32             int middle = (start + end) / 2;
33             CountTask leftTask = new CountTask(start, middle);
34             CountTask rightTask = new CountTask(middle + 1, end);
35             leftTask.fork();
36             rightTask.fork();
37             //等待子任务执行完成  并得到其结果
38             int leftResult = leftTask.join();
39             int rightResult = rightTask.join();
40             //合并子任务
41             sum = leftResult + rightResult;
42         }
43         return sum;
44     }
45     
46     public static void main(String[] args) {
47         ForkJoinPool forkJoinPool = new ForkJoinPool();
48         //生成一个计算任务，负责计算1+2+3+4
49         CountTask task = new CountTask(1,4);
50         //执行一个任务
51         ForkJoinTask<Integer> result = forkJoinPool.submit(task);
52         try {
53             System.out.println(result.get());
54         } catch (InterruptedException e) {
55             e.printStackTrace();
56         } catch (ExecutionException e) {
57             e.printStackTrace();
58         }
59     }
60 }