I am trying to write a recursive sorting algorithm for an array of integers. The following codes prints to the console: 3, 5, 2, 1, 1, 2, 6, 7, 8, 10, 20

The output should be sorted but somehow "it doesn't work".

public static void main(String[] args)
{
    int[] unsortedList = {20, 3, 1, 2, 1, 2, 6, 8, 10, 5, 7};
    duplexSelectionSort(unsortedList, 0, unsortedList.length-1);

    for (int i = 0; i < unsortedList.length; i++)
    {
        System.out.println(unsortedList[i]);
    }
}


public static void duplexSelectionSort(
    int[] unsortedNumbers,
    int startIndex,
    int stopIndex)
{
    int minimumIndex = 0;
    int maximumIndex = 0;

    if (startIndex < stopIndex)
    {
        int index = 0;
        while (index <= stopIndex)
        {
            if (unsortedNumbers[index] < unsortedNumbers[minimumIndex])
            {
                minimumIndex = index;
            }
            if (unsortedNumbers[index] > unsortedNumbers[maximumIndex])
            {
                maximumIndex = index;
            }
            index++;
        }
        swapEdges(unsortedNumbers, startIndex, stopIndex, minimumIndex, maximumIndex);
        duplexSelectionSort(unsortedNumbers, startIndex + 1, stopIndex - 1);
    }
}


public static void swapEdges(
    int[] listOfIntegers,
    int startIndex,
    int stopIndex,
    int minimumIndex,
    int maximumIndex)
{
    if ((minimumIndex == stopIndex) && (maximumIndex == startIndex))
    {
        swap(listOfIntegers, startIndex, stopIndex);
    }
    else
    {
        if (maximumIndex == startIndex)
        {
            swap(listOfIntegers, maximumIndex, stopIndex);
            swap(listOfIntegers, minimumIndex, startIndex);
        }
        else
        {
            swap(listOfIntegers, minimumIndex, startIndex);
            swap(listOfIntegers, maximumIndex, stopIndex);
        }
    }
}

public static void swap(int[] listOfIntegers,
    int index1,
    int index2)
{
    int savedElementAtIndex1 = listOfIntegers[index1];
    listOfIntegers[index1] = listOfIntegers[index2];
    listOfIntegers[index2] = savedElementAtIndex1;
}