*
 * @author Louis Wasserman
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
final class SortedMultisets {
  private SortedMultisets() {}

  /** A skeleton implementation for {@link SortedMultiset#elementSet}. */
  @SuppressWarnings("JdkObsolete") // TODO(b/6160855): Switch GWT emulations to NavigableSet.

  @Override
  public NavigableSet<E> elementSet() {
    NavigableSet<E> result = elementSet;
    if (result == null) {
      return elementSet = new SortedMultisets.NavigableElementSet<>(this);
    }
    return result;
  }

  @Override
  @CheckForNull
  public Entry<E> pollFirstEntry() {
    return forwardMultiset().pollLastEntry();
  }

  @Override

  }

  @Nullable private transient SortedSet<E> elementSet;

  @Override
  public SortedSet<E> elementSet() {
    SortedSet<E> result = elementSet;
    if (result == null) {
      return elementSet = new SortedMultisets.ElementSet<E>(this);
    }
    return result;
  }

  @Override
  @CheckForNull
  public Entry<E> pollFirstEntry() {
    return forwardMultiset().pollLastEntry();
  }

  @Override

  @Override
  public NavigableSet<E> elementSet() {
    NavigableSet<E> result = elementSet;
    if (result == null) {
      return elementSet = new SortedMultisets.NavigableElementSet<>(this);
    }
    return result;
  }

  @Override
  @CheckForNull
  public Entry<E> pollFirstEntry() {
    return forwardMultiset().pollLastEntry();
  }

  @Override

   * situations, you may wish to override {@link SortedMultiset#elementSet} to forward to this
   * implementation or a subclass thereof.
   *
   * @since 15.0
   */
  protected class StandardElementSet extends SortedMultisets.NavigableElementSet<E> {
    /** Constructor for use by subclasses. */
    public StandardElementSet() {
      super(ForwardingSortedMultiset.this);
    }
  }

  @Override

   * situations, you may wish to override {@link SortedMultiset#elementSet} to forward to this
   * implementation or a subclass thereof.
   */
  protected class StandardElementSet extends SortedMultisets.ElementSet<E> {
    /** Constructor for use by subclasses. */
    public StandardElementSet() {
      super(ForwardingSortedMultiset.this);
    }
  }

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