作用：将大任务分解为小任务，然后把每个小任务的结果汇总，得到的是大任务的结果

什么是工作窃取算法

如何使用Fork/Join

创建任务：通过ForkJoinTask的两个子类定义任务。
1. RecursiveAction：用于没有返回结果的任务
2. RecursiveTask：用于有结果的任务

执行者：ForkJoinPool

实例

需求：1+2+…+10000 ```java public class CountTask extends RecursiveTask {

private static final int THRESHOLD = 2;

private int start; private int end;

public CountTask(int start, int end) {

 this.start = start;
 this.end = end;

}

@Override protected Integer compute() {

 int sum = 0;
 boolean canCompute = (end - start) <= THRESHOLD;
 if (canCompute) {
     for (int i = start; i <= end; i++) {
         sum += i;
     }
 } else {
     int middle = (start + end) / 2;
     CountTask left = new CountTask(start, middle);
     CountTask right = new CountTask(middle + 1, end);
     left.fork();
     right.fork();
     int leftR = left.join();
     int rightR = right.join();
     sum = leftR + rightR;
 }
 return sum;

} }

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public static void main(String[] args) throws ExecutionException, InterruptedException { ForkJoinPool forkJoinPool = new ForkJoinPool(); CountTask countTask = new CountTask(1, 100); ForkJoinTask submit = forkJoinPool.submit(countTask); System.out.println(submit.get()); } ```