/**
 * Implementation of {@link Multisets#unmodifiableSortedMultiset(SortedMultiset)} for GWT.
 *
 * @author Louis Wasserman
 */
@ElementTypesAreNonnullByDefault
final class UnmodifiableSortedMultiset<E extends @Nullable Object> extends UnmodifiableMultiset<E>
    implements SortedMultiset<E> {
  UnmodifiableSortedMultiset(SortedMultiset<E> delegate) {
    super(delegate);
  }

  @Override

    return (NavigableSet<E>) super.elementSet();
  }

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

  @Override
  public SortedMultiset<E> descendingMultiset() {
    UnmodifiableSortedMultiset<E> result = descendingMultiset;
    if (result == null) {
      result = new UnmodifiableSortedMultiset<>(delegate().descendingMultiset());
      result.descendingMultiset = this;

    return new TestStringMultisetGenerator() {
      @Override
      protected Multiset<String> create(String[] elements) {
        return Multisets.unmodifiableSortedMultiset(TreeMultiset.create(asList(elements)));
      }

      @Override
      public List<String> order(List<String> insertionOrder) {
        sort(insertionOrder);
        return insertionOrder;
      }

    return new TestStringMultisetGenerator() {
      @Override
      protected Multiset<String> create(String[] elements) {
        return Multisets.unmodifiableSortedMultiset(TreeMultiset.create(asList(elements)));
      }

      @Override
      public List<String> order(List<String> insertionOrder) {
        sort(insertionOrder);
        return insertionOrder;
      }