@Override
    public List<Integer> sort(List<Integer> list) {

        // checking input parameter for null
        if (list == null) {
            throw new IllegalArgumentException("ArrayList not specified!");
        }

        int i, j;

        // moving forward through array.
        for (i = 1; i < list.size(); i++) {
            j = i;

            // moving element back, while element bigger than others.
            while (j > 0 && list.get(j - 1) > list.get(j)) {
                appUtil.swap(list, j, j - 1);
                j--;
            }
        }
        return list;
    }