Implementation of BubbleSort in Java.

BubbleSort.java

/**
 * @file
 *  Bubble sort class.
 */

public class BubbleSort {

	/**
	 * Printing vector method.
	 *
	 * Prints on screen the elements of the vector, from first to last element.
	 *
	 * @param int[] a
	 *  Vector of integers.
	 * @return void
	 */
	public static void print_vector(int[] a) {

		if (a == null) {
			System.out.println("Null vector.");
			return;
		}

		System.out.println();

		System.out.print("< ");

		for (int i = 0; i < a.length; i++) {

	        System.out.print(a[i] + ", ");
    	}

    	System.out.print(" >");

    	System.out.println();
	}


	/**
	 * Bubble sort.
	 *
	 * Iterative version.
	 *
	 * Sort order: ascending.
	 *
	 * @param int[] a
	 *  Vector of integers.
	 * @return int[]
	 *  Arranged vector in ascending order.
	 */
	public static int[] bubble_sort_iterative_ascending(int[] a) {

		if (a == null) return null;

		for(int i = 0; i < a.length; i++) {

			boolean swapped = false;

			for (int j = 1; j < a.length - i; j++) {
				
				if (a[j - 1] > a[j]) {
					
					int aux = a[j - 1];
					a[j - 1] = a[j];
					a[j] = aux;

					swapped = true;
				}
			}

			if (!swapped) break;
		}

		return a;
	}


	/**
	 * Bubble sort.
	 *
	 * Iterative version.
	 *
	 * Sort order: descending.
	 *
	 * @param int[] a
	 *  Vector of integers.
	 * @return int[]
	 *  Arranged vector in descending order.
	 */
	public static int[] bubble_sort_iterative_descending(int[] a) {

		if (a == null) return null;

		for(int i = 0; i < a.length; i++) {

			boolean swapped = false;

			for (int j = 1; j < a.length - i; j++) {
				
				if (a[j - 1] < a[j]) {
					
					int aux = a[j - 1];
					a[j - 1] = a[j];
					a[j] = aux;

					swapped = true;
				}
			}

			if (!swapped) break;
		}

		return a;
	}


	/**
	 * Bubble sort.
	 *
	 * Recursive version.
	 *
	 * Sort order: ascending.
	 *
	 * @param int[] a
	 *  Vector of integers.
	 * @return int[]
	 *  Arranged vector in ascending order.
	 */
	public static int[] bubble_sort_recursive_ascending(int[] a, int i, int j, boolean swapped) {

		if (a == null) return null;

		if (i >= a.length) {
			return a;
		}

		if (j < a.length - i) {
			
			if (a[j - 1] > a[j]) {
				
				int aux = a[j - 1];
				a[j - 1] = a[j];
				a[j] = aux;

				swapped = true;
			}

			return bubble_sort_recursive_ascending(a, i, j + 1, swapped);
		}

		if(!swapped) return a;

		return bubble_sort_recursive_ascending(a, i + 1, 1, false);
	}


	/**
	 * Overloading of bubble_sort_recursive_ascending() method.
	 *
	 * Simplifies the call of the method.
	 */
	public static int[] bubble_sort_recursive_ascending(int[] a) {

		return bubble_sort_recursive_ascending(a, 0, 1, false);
	}


	/**
	 * Bubble sort.
	 *
	 * Recursive version.
	 *
	 * Sort order: descending.
	 *
	 * @param int[] a
	 *  Vector of integers.
	 * @return int[]
	 *  Arranged vector in descending order.
	 */
	public static int[] bubble_sort_recursive_descending(int[] a, int i, int j, boolean swapped) {

		if (a == null) return null;

		if (i >= a.length) {
			return a;
		}

		if (j < a.length - i) {
			
			if (a[j - 1] < a[j]) {
				
				int aux = a[j - 1];
				a[j - 1] = a[j];
				a[j] = aux;

				swapped = true;
			}

			return bubble_sort_recursive_descending(a, i, j + 1, swapped);
		}

		if(!swapped) return a;

		return bubble_sort_recursive_descending(a, i + 1, 1, false);
	}


	/**
	 * Overloading of bubble_sort_recursive_descending() method.
	 *
	 * Simplifies the call of the method.
	 */
	public static int[] bubble_sort_recursive_descending(int[] a) {

		return bubble_sort_recursive_descending(a, 0, 1, false);
	}
	

	/**
	 * Examples of use.
	 */
    public static void main(String args[]) {

    	int[] a = { 24, 4, 67, 4, 3, 5, 6, 6, 7, 34, 12, 12, 24, 35, 2, 24, 45, 56, 78 };

    	BubbleSort.bubble_sort_iterative_ascending(a);

    	System.out.println("Initial vector:");
    	print_vector(a);
    }
}