QuickSort & ForkJoin

ForkJoinExample.java

/*
 *  Copyright 2016 ADVA Optical Networking SE. All rights reserved.
 *
 *  Owner: erohana
 *
 *  $Id: $
 */
package multithread;

import java.util.Arrays;
import java.util.Random;
import java.util.concurrent.ForkJoinPool;

public class ForkJoinExample {

  private static final int SIZE = 10000;

  public static void main(String[] args) {
    int[] data1 = new int[SIZE];
    Random rand = new Random();
    for (int i = 0; i < data1.length; i++) {
      int randomNum = rand.nextInt((SIZE) + 1);

      data1[i] = randomNum;

    }
    QuickSortAction quickSort = new QuickSortAction(data1);

    ForkJoinPool pool = new ForkJoinPool();
    pool.invoke(quickSort);

    pool.shutdown();

    System.out.println("data = " + Arrays.toString(data1));
  }
}

QuickSortAction.java

package multithread;

import java.util.concurrent.RecursiveAction;

/**
 * Quick Sort based on Hoare partition scheme using {@link java.util.concurrent.ForkJoinPool}
 */
public class QuickSortAction extends RecursiveAction{
  private int[] data;
  private int left;
  private int right;

  public QuickSortAction(int[] data) {
    this.data = data;
    left = 0;
    right = data.length - 1;
  }

  public QuickSortAction(int[] data, int left, int right) {
    this.data = data;
    this.left = left;
    this.right = right;
  }


  @Override
  protected void compute() {
    if(left < right){
      int pivot = partition(data, left, right);
      invokeAll(new QuickSortAction(data,left, pivot),
                new QuickSortAction(data, pivot + 1, right));
    }
  }

  private int partition(int[] array, int low, int high) {
    int pivot = array[low];
    int i = low - 1;
    int j  = high + 1;
    while (true){
      do {
        i++;
      }
      while (array[i] < pivot);

      do {
        j--;
      }
      while (array[j] > pivot);
      if (i >= j)
        return j;

      swap(array, i, j);
    }
  }

  private void swap(int[] array, int i, int j) {
    int temp = array[i];
    array[i] = array[j];
    array[j] = temp;
  }
}