}

    @Override
    public NavigableSet<E> headSet(@ParametricNullness E toElement, boolean inclusive) {
      return new NavigableElementSet<>(
          multiset().headMultiset(toElement, BoundType.forBoolean(inclusive)));
    }

    @Override
    public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclusive) {
      return new NavigableElementSet<>(

      derivedSuites.add(createSubMultisetSuite(parentBuilder, Bound.INCLUSIVE, Bound.EXCLUSIVE));
      derivedSuites.add(createSubMultisetSuite(parentBuilder, Bound.INCLUSIVE, Bound.INCLUSIVE));
    }

    return derivedSuites;
  }

  private TestSuite createSubMultisetSuite(
      SortedMultisetTestSuiteBuilder<E> parentBuilder, Bound from, Bound to) {
    TestMultisetGenerator<E> delegate =

      for (List<Integer> contents : SAMPLE_INPUTS) {
        for (int i = 0; i < 10; i++) {
          for (boolean inclusive : ImmutableList.of(true, false)) {
            assertEquals(
                filter(createUnfiltered(contents).headSet(i, inclusive), EVEN),
                filter(createUnfiltered(contents), EVEN).headSet(i, inclusive));
          }
        }
      }
    }

    public void testNavigableTailSet() {

      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.NO_BOUND));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.EXCLUSIVE));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.INCLUSIVE));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.INCLUSIVE, Bound.INCLUSIVE));
    }

    return derivedSuites;

    @Override
    public NavigableMap<Cut<C>, Range<C>> headMap(Cut<C> toKey, boolean inclusive) {
      return subMap(Range.upTo(toKey, BoundType.forBoolean(inclusive)));
    }

    @Override
    public NavigableMap<Cut<C>, Range<C>> tailMap(Cut<C> fromKey, boolean inclusive) {
      return subMap(Range.downTo(fromKey, BoundType.forBoolean(inclusive)));
    }

    @Override
    public Comparator<? super Cut<C>> comparator() {

  /**
   * File Separator: These four information separators may be used within data in optional fashion,
   * except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then
   * RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are
   * not specified.)
   *
   * @since 8.0
   */
  public static final byte FS = 28;

  /**

        : new EmptyContiguousSet<C>(domain);
  }

  @Override
  ContiguousSet<C> headSetImpl(C toElement, boolean inclusive) {
    return intersectionInCurrentDomain(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
  }

  @Override
  @SuppressWarnings("unchecked") // TODO(cpovirk): Use a shared unsafeCompare method.
  ContiguousSet<C> subSetImpl(

    @Override
    public NavigableSet<V> headSet(@ParametricNullness V toElement, boolean inclusive) {
      return wrap(getSortedSetDelegate().headSet(toElement, inclusive));
    }

    @Override
    public NavigableSet<V> tailSet(@ParametricNullness V fromElement, boolean inclusive) {
      return wrap(getSortedSetDelegate().tailSet(fromElement, inclusive));
    }
  }

    ImmutableSortedSet<C> subSet(Range<C> range) {
      return subRangeSet(range).asSet(domain);
    }

    @Override
    ImmutableSortedSet<C> headSetImpl(C toElement, boolean inclusive) {
      return subSet(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
    }

    @Override
    ImmutableSortedSet<C> subSetImpl(
        C fromElement, boolean fromInclusive, C toElement, boolean toInclusive) {

    ImmutableSortedSet<E> set = headSet(e, true);
    return !set.isEmpty() ? set.last() : null;
  }

  public ImmutableSortedSet<E> headSet(E toElement, boolean inclusive) {
    checkNotNull(toElement);
    if (inclusive) {
      E tmp = higher(toElement);
      if (tmp == null) {
        return this;
      }
      toElement = tmp;
    }
    return headSet(toElement);
  }