package com.example.foo;

import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;

/**
 * https://humanoidreadable.wordpress.com/2014/12/31/forkjoin-nonrecursive-task/
 * 
 * @author Claude Martin
 *
 */
public class SomeClass {

  private static class Task1 extends ForkJoinTask<Integer> {
    private static final long serialVersionUID = 4577085552193799470L;

    private final Integer input;
    private Integer result = null;

    public Task1(Integer input) {
      this.input = input;
    }

    @Override
    public Integer getRawResult() {
      return this.result;
    }

    @Override
    protected void setRawResult(Integer value) {
      this.result = value;
    }

    @Override
    protected boolean exec() {
      ForkJoinTask<Integer> a = new Task2(this.input).fork();
      ForkJoinTask<Integer> b = new Task2(this.input + 1).fork();
      setRawResult(a.join() + b.join());
      return true;
    }
  }

  private static class Task2 extends ForkJoinTask<Integer> {
    private static final long serialVersionUID = -7037328571331917872L;
    private final Integer input;
    private Integer result = null;

    public Task2(Integer input) {
      this.input = input;
    }

    @Override
    public Integer getRawResult() {
      return this.result;
    }

    @Override
    protected void setRawResult(Integer value) {
      this.result = value;
    }

    @Override
    protected boolean exec() {
      System.out.format("Task2(%d) started%n", this.input);

      // This is the actual work:
      setRawResult(this.input * this.input);

      // Just to show that they really run in parallel:
      try {
        Thread.sleep(5000);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }

      System.out.format("Task2(%d) finished%n", this.input);
      return true;
    }
  }

  public static void main(String[] args) {

    Integer result = ForkJoinPool.commonPool().invoke(new Task1(5));
    System.out.println(result);

    // 5*5 = 25
    // 6*6 = 36
    // 25+36= 61

  }
}