Fork,Join实例

版权声明：本文为博主原创文章，转载请说明出处 https://blog.csdn.net/u010002184/article/details/83343059

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.Future;
import java.util.concurrent.RecursiveTask;
import java.util.concurrent.atomic.AtomicIntegerArray;

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;
    }

    public int getStart() {
        return start;
    }

    public int getEnd() {
        return end;
    }

    @Override
    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);
            System.out.println("leftTask:" + leftTask.getStart() + "," + leftTask.getEnd());
            System.out.println("rightTask:" + rightTask.getStart() + "," + rightTask.getEnd());
            // 执行子任务
            leftTask.fork();//每个子任务在调用fork方法时，又会进入compute方法
            rightTask.fork();
            // 等待子任务执行完，并得到其结果
            int leftResult = leftTask.join();
            int rightResult = rightTask.join();
            System.out.println(leftResult + "," + rightResult);
            // 合并子任务
            sum = leftResult + rightResult;
        }
        return sum;
    }


    public static void main(String[] args) {
        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, 10);
        // 执行一个任务
        Future<Integer> result = forkJoinPool.submit(task);
        try {
            System.out.println(result.get());
        } catch (InterruptedException e) {
        } catch (ExecutionException e) {
        }

        //------------------------

        int[] value = new int[]{1, 2};
        AtomicIntegerArray ai = new AtomicIntegerArray(value);
        System.out.println(ai.getAndSet(0, 3));//返回原来的值
        System.out.println(ai.get(0));
        System.out.println(value[0]);

    }
}

输出：

leftTask:1,5
rightTask:6,10
leftTask:1,3
rightTask:4,5
6,9
leftTask:6,8
rightTask:9,10
21,19
15,40
55