}

      ImmutableRangeSet<Integer> built = builder.build();
      assertEquals(mutable, built);
      assertEquals(ImmutableRangeSet.copyOf(mutable), built);
      assertEquals(mutable.complement(), built.complement());

      for (int i = 0; i <= 11; i++) {
        assertEquals(mutable.contains(i), built.contains(i));
      }

      SerializableTester.reserializeAndAssert(built);

    } else {
      rangesByLowerBound.put(range.lowerBound, range);
    }
  }

  @LazyInit @CheckForNull private transient RangeSet<C> complement;

  @Override
  public RangeSet<C> complement() {
    RangeSet<C> result = complement;
    return (result == null) ? complement = new Complement() : result;
  }

  @VisibleForTesting
  static final class RangesByUpperBound<C extends Comparable<?>>

      }

      ImmutableRangeSet<Integer> built = builder.build();
      assertEquals(mutable, built);
      assertEquals(ImmutableRangeSet.copyOf(mutable), built);
      assertEquals(mutable.complement(), built.complement());

      for (int i = 0; i <= 11; i++) {
        assertEquals(mutable.contains(i), built.contains(i));
      }

      SerializableTester.reserializeAndAssert(built);

    }
  }

  @Override
  public ImmutableRangeSet<C> complement() {
    ImmutableRangeSet<C> result = complement;
    if (result != null) {
      return result;
    } else if (ranges.isEmpty()) {
      return complement = all();
    } else if (ranges.size() == 1 && ranges.get(0).equals(Range.all())) {
      return complement = of();
    } else {

    }
  }

  @Override
  public ImmutableRangeSet<C> complement() {
    ImmutableRangeSet<C> result = complement;
    if (result != null) {
      return result;
    } else if (ranges.isEmpty()) {
      return complement = all();
    } else if (ranges.size() == 1 && ranges.get(0).equals(Range.all())) {
      return complement = of();
    } else {

   * @since 19.0
   */
  Set<Range<C>> asDescendingSetOfRanges();

  /**
   * Returns a view of the complement of this {@code RangeSet}.
   *
   * <p>The returned view supports the {@link #add} operation if this {@code RangeSet} supports
   * {@link #remove}, and vice versa.
   */
  RangeSet<C> complement();

  /**
   * Returns a view of the intersection of this {@code RangeSet} with the specified range.
   *

  }

  @J2ktIncompatible
  @GwtIncompatible // complementOf
  public void testComplementOfEnumSet() {
    Set<SomeEnum> units = EnumSet.of(SomeEnum.B, SomeEnum.D);
    EnumSet<SomeEnum> otherUnits = Sets.complementOf(units);
    verifySetContents(otherUnits, EnumSet.of(SomeEnum.A, SomeEnum.C));
  }

  @J2ktIncompatible
  @GwtIncompatible // complementOf
  public void testComplementOfEnumSetWithType() {

    bus.register(compCatcher);

    // Two additional event types: Object and Comparable<?> (played by Integer)
    Object objEvent = new Object();
    Object compEvent = 6;

    bus.post(EVENT);
    bus.post(objEvent);
    bus.post(compEvent);

    // Check the StringCatcher...
    List<String> stringEvents = stringCatcher.getEvents();
    assertEquals("Only one String should be delivered.", 1, stringEvents.size());

    bus.register(compCatcher);

    // Two additional event types: Object and Comparable<?> (played by Integer)
    Object objEvent = new Object();
    Object compEvent = 6;

    bus.post(EVENT);
    bus.post(objEvent);
    bus.post(compEvent);

    // Check the StringCatcher...
    List<String> stringEvents = stringCatcher.getEvents();
    assertEquals("Only one String should be delivered.", 1, stringEvents.size());

 *       create a "fake" converter for a unit test. It is unnecessary (and confusing) to <i>mock</i>
 *       the {@code Converter} type using a mocking framework.
 *   <li>Extend this class and implement its {@link #doForward} and {@link #doBackward} methods.
 *   <li><b>Java 8+ users:</b> you may prefer to pass two lambda expressions or method references to
 *       the {@link #from from} factory method.
 * </ul>
 *