Java并发-23.Fork/Join框架

package com.junzerg.threads;

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

/**
 * @author pengjunzhe
 */
public class CountTask extends RecursiveTask<Integer> {

    /**
     * 阈值
     */
    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;
        // 如果任务足够小，就直接计算任务
        boolean canComputer = (end - start) < THRESHOLD;
        if (canComputer) {
            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来计算
            int middle = (end + start) / 2;
            CountTask leftTask = new CountTask(start, middle);
            CountTask rightTask = new CountTask(middle + 1, end);
            leftTask.fork();
            rightTask.fork();
            // 等待子任务执行完，得到结果
            int leftResult = leftTask.join();
            int rightResult = rightTask.join();
            sum = leftResult + rightResult;
        }
        return sum;
    }

    public static void main(String[] args) throws InterruptedException {
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        CountTask task = new CountTask(1,4);
        Future<Integer> result = forkJoinPool.submit(task);
        try{
            System.out.println(result.get());
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }
}