gistfile1.txt

public static <E extends Comparable<E>> void quickSort(ArrayList<E> arr, int low, int high) {
        if (arr == null || arr.size() == 0)
            return;

        if (low >= high)
            return;

        // pick the pivot
        int middle = low + (high - low) / 2;
        E pivotLength = arr.get(middle);

        // make left < pivot and right > pivot
        int i = low, j = high;
        while (i <= j) {
            while (arr.get(i).compareTo(pivotLength) < 0) {
                i++;
            }

            while (arr.get(j).compareTo(pivotLength) > 0) {
                j--;
            }

            if (i <= j) {
                E temp = arr.get(i);
                arr.set(i, arr.get(j));
                arr.set(j, temp);
                i++;
                j--;
            }
        }

        // recursively sort two sub parts
        if (low < j)
            quickSort(arr, low, j);

        if (high > i)
            quickSort(arr, i, high);
    }