* builder.
     *
     * @throws IllegalArgumentException if any two ranges inserted into this builder overlap
     */
    public ImmutableRangeMap<K, V> build() {
      sort(entries, Range.<K>rangeLexOrdering().onKeys());
      ImmutableList.Builder<Range<K>> rangesBuilder = new ImmutableList.Builder<>(entries.size());
      ImmutableList.Builder<V> valuesBuilder = new ImmutableList.Builder<>(entries.size());

     * builder.
     *
     * @throws IllegalArgumentException if any two ranges inserted into this builder overlap
     */
    public ImmutableRangeMap<K, V> build() {
      sort(entries, Range.<K>rangeLexOrdering().onKeys());
      ImmutableList.Builder<Range<K>> rangesBuilder = new ImmutableList.Builder<>(entries.size());
      ImmutableList.Builder<V> valuesBuilder = new ImmutableList.Builder<>(entries.size());

                  @Override
                  public Iterable<Entry<Range<Integer>, String>> order(
                      List<Entry<Range<Integer>, String>> insertionOrder) {
                    return Range.<Integer>rangeLexOrdering().onKeys().sortedCopy(insertionOrder);
                  }

                  @SuppressWarnings("unchecked")
                  @Override
                  public Range<Integer>[] createKeyArray(int length) {

      return ImmutableSet.of();
    }
    return new RegularImmutableSortedSet<>(ranges, Range.rangeLexOrdering());
  }

  @Override
  public ImmutableSet<Range<C>> asDescendingSetOfRanges() {
    if (ranges.isEmpty()) {
      return ImmutableSet.of();
    }
    return new RegularImmutableSortedSet<>(ranges.reverse(), Range.<C>rangeLexOrdering().reverse());
  }

  private static final class ComplementRanges<C extends Comparable>