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
     
       {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     @Override22     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+449         CountTask task = new CountTask(1,4);50         //执行一个任务51         ForkJoinTask
      
        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 }