并发执行任务

 

 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 }