public void mergeSort (int first, int last)
    {
        if (first < last)
        {
            int middle = (first + last) / 2;
            mergeSort(first,middle);
            mergeSort(middle+1,last);
            merge(first,middle,last);
        }
    }
public void merge (int first, int middle, int last)
    {
        int [] temp = new int[last-first+1];
        int first1 = first;
        int last1 = middle;
        int first2 = middle + 1;
        int last2 = last;
        int index = 0;
        while ((first1 <= last1) && (first2 <= last2))
        {
            if (list[first1] < list[first2])
            {
                temp[index] = list[first1];
                first1++;
            }
            else
            {
                temp[index] = list[first2];
                first2++;
            }
            index++;
        }
while (first1 <= last1)
        {
            temp[index] = list[first1];
            first1++;
            index++;
        }

        while (first2 <= last2)
        {
            temp[index] = list[first2];
            first2++;
            index++;
        }

        int listIndex = first;
        for (index = 0; index < temp.length; index++)
        {
            list[listIndex] = temp[index];
            listIndex++;
        }
}