Implementation of QuickSort in Java.

QuickSorter.java

package jono.sorting;

import java.util.Arrays;
import java.util.stream.Stream;


public class QuickSorter {
  public static void main(String[] args) {
    QuickSorter sorter = new QuickSorter();

    int[] array = Stream.of(args[0].split(",")).mapToInt(Integer::parseInt).toArray();

    sorter.sort(array);
    System.out.println(Arrays.toString(array));
  }

  public void sort(int[] numbers) {
    quickSort(numbers, 0, numbers.length - 1);
  }

  private void quickSort(int[] numbers, int left, int right) {
    int divPoint, pivot;

    if (left >= right) {
      return;
    }

    System.out.printf("left: %d right: %d%n", left, right);
    pivot = numbers[(left + right) / 2];

    divPoint = partition(numbers, left, right, pivot);
    System.out.println("divPoint: " + divPoint);

    quickSort(numbers, left, divPoint - 1);
    quickSort(numbers, divPoint, right);
  }

  private int partition(int[] numbers, int left, int right, int pivot) {
    while (left <= right) {
      while (numbers[left] < pivot) {
        left += 1;
      }

      while (numbers[right] > pivot) {
        right -= 1;
      }

      if (left <= right) {
          swap(numbers, left, right);

          left += 1;
          right -= 1;
      }
    }

    return left;
  }

  private void swap(int[] numbers, int left, int right) {
    int leftNum = numbers[left];
    int rightNum = numbers[right];

    numbers[left] = rightNum;
    numbers[right] = leftNum;
  }
}