Recursive quicksort algorithm

quickSort.java

public static void quickSort(int[] array, int left, int right) {
    if (left < right) {
        int pivotIndex = partition(array, left, right); // the pivot is already on its place
        quickSort(array, left, pivotIndex - 1);  // sort the left subarray
        quickSort(array, pivotIndex + 1, right); // sort the right subarray 
    }
}

private static int partition(int[] array, int left, int right) {
    int pivot = array[right];  // choose the rightmost element as the pivot
    int partitionIndex = left; // the first element greater than the pivot

    /* move large values into the right side of the array */
    for (int i = left; i < right; i++) {
        if (array[i] <= pivot) { // may be used '<' as well
            swap(array, i, partitionIndex);
            partitionIndex++;
        }
    }

    swap(array, partitionIndex, right); // put the pivot on a suitable position

    return partitionIndex;
}

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