* returns a {@code NavigableSet}.)
   */
  @Override
  SortedSet<E> elementSet();

  SortedMultiset<E> descendingMultiset();

  SortedMultiset<E> headMultiset(E upperBound, BoundType boundType);

  SortedMultiset<E> subMultiset(
      E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType);

  SortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType);

 *
 * @author Louis Wasserman
 * @since 11.0
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public interface SortedMultiset<E extends @Nullable Object>
    extends SortedMultisetBridge<E>, SortedIterable<E> {
  /**
   * Returns the comparator that orders this multiset, or {@link Ordering#natural()} if the natural

final class UnmodifiableSortedMultiset<E extends @Nullable Object> extends UnmodifiableMultiset<E>
    implements SortedMultiset<E> {
  UnmodifiableSortedMultiset(SortedMultiset<E> delegate) {
    super(delegate);
  }

  @Override
  protected SortedMultiset<E> delegate() {
    return (SortedMultiset<E>) super.delegate();
  }

  @Override
  public Comparator<? super E> comparator() {
    return delegate().comparator();

    expectAddFailure(sortedMultiset.tailMultiset(b.getElement(), OPEN), b);
    expectAddFailure(sortedMultiset.tailMultiset(c.getElement(), CLOSED), a);
    expectAddFailure(sortedMultiset.tailMultiset(c.getElement(), CLOSED), b);
    expectAddFailure(sortedMultiset.tailMultiset(c.getElement(), OPEN), a);
    expectAddFailure(sortedMultiset.tailMultiset(c.getElement(), OPEN), b);

   * SortedMultiset#contains}, {@link SortedMultiset#containsAll}, {@link SortedMultiset#count},
   * {@link SortedMultiset#firstEntry} {@link SortedMultiset#headMultiset}, {@link
   * SortedMultiset#isEmpty}, {@link SortedMultiset#lastEntry}, {@link SortedMultiset#subMultiset},
   * {@link SortedMultiset#tailMultiset}, the {@code size()} and {@code iterator()} methods of

        .testForwarding(
            SortedMultiset.class,
            new Function<SortedMultiset, SortedMultiset>() {
              @Override
              public SortedMultiset apply(SortedMultiset delegate) {
                return wrap(delegate);
              }
            });
  }

  public void testEquals() {
    SortedMultiset<String> set1 = ImmutableSortedMultiset.of("one");

    expectAddFailure(sortedMultiset.tailMultiset(b.getElement(), OPEN), b);
    expectAddFailure(sortedMultiset.tailMultiset(c.getElement(), CLOSED), a);
    expectAddFailure(sortedMultiset.tailMultiset(c.getElement(), CLOSED), b);
    expectAddFailure(sortedMultiset.tailMultiset(c.getElement(), OPEN), a);
    expectAddFailure(sortedMultiset.tailMultiset(c.getElement(), OPEN), b);

  }

  @Nullable private transient SortedMultiset<E> descendingMultiset;

  @Override
  public SortedMultiset<E> descendingMultiset() {
    SortedMultiset<E> result = descendingMultiset;
    return (result == null) ? descendingMultiset = createDescendingMultiset() : result;
  }

  SortedMultiset<E> createDescendingMultiset() {
    return new DescendingMultiset<E>() {
      @Override

   * SortedMultiset#contains}, {@link SortedMultiset#containsAll}, {@link SortedMultiset#count},
   * {@link SortedMultiset#firstEntry} {@link SortedMultiset#headMultiset}, {@link
   * SortedMultiset#isEmpty}, {@link SortedMultiset#lastEntry}, {@link SortedMultiset#subMultiset},
   * {@link SortedMultiset#tailMultiset}, the {@code size()} and {@code iterator()} methods of

  }

  @LazyInit @CheckForNull private transient SortedMultiset<E> descendingMultiset;

  @Override
  public SortedMultiset<E> descendingMultiset() {
    SortedMultiset<E> result = descendingMultiset;
    return (result == null) ? descendingMultiset = createDescendingMultiset() : result;
  }

  SortedMultiset<E> createDescendingMultiset() {
    @WeakOuter