MyRecursiveTask.java

package com.study.forkjoinpool;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.RecursiveTask;

/**
 * 설명 :
 *
 * @author Hardy(조민국) / dev.mingood@dreamus.io
 * @since 2021. 01. 08
 */
class MyRecursiveTask extends RecursiveTask<Long> {

    private long workLoad;

    public MyRecursiveTask(long workLoad) {
        this.workLoad = workLoad;
    }

    @Override
    protected Long compute() {
        String threadName = Thread.currentThread().getName();

        if (this.workLoad > 16) {
            System.out.println("[" + threadName + "] Splitting workLoad : " + this.workLoad);

            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            List<MyRecursiveTask> subtasks = new ArrayList<>(this.createSubtasks());

            for (MyRecursiveTask subtask : subtasks) {
                subtask.fork();
            }

            long result = 0;
            for (MyRecursiveTask subtask : subtasks) {
                result += subtask.join();
            }
            return result;

        } else {
            System.out.println("Doing workLoad myself: " + this.workLoad);
            return workLoad * 3;
        }
    }

    private List<MyRecursiveTask> createSubtasks() {
        List<MyRecursiveTask> subtasks = new ArrayList<>();

        MyRecursiveTask subtask1 = new MyRecursiveTask(this.workLoad / 2);
        MyRecursiveTask subtask2 = new MyRecursiveTask(this.workLoad / 2);

        subtasks.add(subtask1);
        subtasks.add(subtask2);
        return subtasks;
    }

}