JavaAlgorithms/Sorts/BubbleSortRecursion.java

package Sorts;

import java.util.Random;

/** BubbleSort algorithm implements using recursion */
public class BubbleSortRecursion implements SortAlgorithm {
  public static void main(String[] args) {
    Integer[] array = new Integer[10];

    Random random = new Random();
    /* generate 10 random numbers from -50 to 49 */
    for (int i = 0; i < array.length; ++i) {
      array[i] = random.nextInt(100) - 50;
    }

    BubbleSortRecursion bubbleSortRecursion = new BubbleSortRecursion();
    bubbleSortRecursion.sort(array);

    /* check array is sorted or not */
    for (int i = 0; i < array.length - 1; ++i) {
      assert (array[i].compareTo(array[i + 1]) <= 0);
    }
  }

  /**
   * @param unsorted - an array should be sorted
   * @return sorted array
   */
  @Override
  public <T extends Comparable<T>> T[] sort(T[] unsorted) {
    bubbleSort(unsorted, unsorted.length);
    return unsorted;
  }

  /**
   * BubbleSort algorithm implements using recursion
   *
   * @param unsorted array contains elements
   * @param len length of given array
   */
  private static <T extends Comparable<T>> void bubbleSort(T[] unsorted, int len) {
    boolean swapped = false; /* flag to check if array is sorted or not */
    for (int i = 0; i < len - 1; ++i) {
      if (SortUtils.greater(unsorted[i], unsorted[i + 1])) {
        SortUtils.swap(unsorted, i, i + 1);
        swapped = true;
      }
    }
    if (swapped) {
      bubbleSort(unsorted, len - 1);
    }
  }
}