checkNotNull(elements);
    Comparator<?> comparator2;
    if (elements instanceof SortedSet) {
      comparator2 = comparator((SortedSet<?>) elements);
    } else if (elements instanceof SortedIterable) {
      comparator2 = ((SortedIterable<?>) elements).comparator();
    } else {
      return false;
    }
    return comparator.equals(comparator2);
  }

  @SuppressWarnings("unchecked")

 * SortedSet} for GWT compatibility.
 *
 * @author Louis Wasserman
 * @since 11.0
 */
public interface SortedMultiset<E extends @Nullable Object> extends Multiset<E>, SortedIterable<E> {
  Comparator<? super E> comparator();

  @Nullable Entry<E> firstEntry();

  @Nullable Entry<E> lastEntry();

  @Nullable Entry<E> pollFirstEntry();

  @Nullable Entry<E> pollLastEntry();

/**
 * GWT emulation of {@link com.google.common.collect.ImmutableSortedSet}.
 *
 * @author Hayward Chan
 */
public abstract class ImmutableSortedSet<E> extends ForwardingImmutableSet<E>
    implements SortedSet<E>, SortedIterable<E> {
  // TODO(cpovirk): split into ImmutableSortedSet/ForwardingImmutableSortedSet?

  // In the non-emulated source, this is in ImmutableSortedSetFauxverideShim,

@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableSortedSet<E> extends ImmutableSet<E>
    implements NavigableSet<E>, SortedIterable<E> {
  /**
   * Returns a {@code Collector} that accumulates the input elements into a new {@code
   * ImmutableSortedSet}, ordered by the specified comparator.
   *