*/
@GwtCompatible
abstract class AbstractSortedMultiset<E extends @Nullable Object> extends AbstractMultiset<E>
    implements SortedMultiset<E> {
  private final Comparator<? super E> comparator;

  // needed for serialization
  @SuppressWarnings("unchecked")
  AbstractSortedMultiset() {
    this((Comparator) Ordering.natural());
  }

  AbstractSortedMultiset(Comparator<? super E> comparator) {

 *
 * @author Louis Wasserman
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible
public final class TreeMultiset<E extends @Nullable Object> extends AbstractSortedMultiset<E>
    implements Serializable {

  /**
   * Creates a new, empty multiset, sorted according to the elements' natural order. All elements

 *
 * @author Louis Wasserman
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible
public final class TreeMultiset<E extends @Nullable Object> extends AbstractSortedMultiset<E>
    implements Serializable {

  /**
   * Creates a new, empty multiset, sorted according to the elements' natural order. All elements