@Override
    protected SortedSet<Integer> create(Integer[] elements) {
      return checkedCreate(nullCheckedTreeSet(elements)).descendingSet();
    }

    /** Sorts the elements in reverse natural order. */
    @Override
    public List<Integer> order(List<Integer> insertionOrder) {
      Collections.sort(insertionOrder, Ordering.<Integer>natural().reverse());
      return insertionOrder;

    @Override
    protected SortedSet<Integer> create(Integer[] elements) {
      return checkedCreate(nullCheckedTreeSet(elements)).descendingSet();
    }

    /** Sorts the elements in reverse natural order. */
    @Override
    public List<Integer> order(List<Integer> insertionOrder) {
      Collections.sort(insertionOrder, Ordering.<Integer>natural().reverse());
      return insertionOrder;