/**
 * Implementation for {@link FilteredMultimap#values()}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
final class FilteredMultimapValues<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractCollection<V> {
  @Weak private final FilteredMultimap<K, V> multimap;

  FilteredMultimapValues(FilteredMultimap<K, V> multimap) {
    this.multimap = checkNotNull(multimap);
  }

/**
 * A supertype for filtered {@link SetMultimap} implementations.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
interface FilteredSetMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends FilteredMultimap<K, V>, SetMultimap<K, V> {
  @Override
  SetMultimap<K, V> unfiltered();

/**
 * A supertype for filtered {@link SetMultimap} implementations.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
interface FilteredSetMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends FilteredMultimap<K, V>, SetMultimap<K, V> {
  @Override
  SetMultimap<K, V> unfiltered();

 *
 * @author Louis Wasserman
 */
@GwtCompatible
class FilteredKeyMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMultimap<K, V> implements FilteredMultimap<K, V> {
  final Multimap<K, V> unfiltered;
  final Predicate<? super K> keyPredicate;

  FilteredKeyMultimap(Multimap<K, V> unfiltered, Predicate<? super K> keyPredicate) {
    this.unfiltered = checkNotNull(unfiltered);

      return new FilteredKeyMultimap<>(
          prev.unfiltered, Predicates.and(prev.keyPredicate, keyPredicate));
    } else if (unfiltered instanceof FilteredMultimap) {
      FilteredMultimap<K, V> prev = (FilteredMultimap<K, V>) unfiltered;
      return filterFiltered(prev, Maps.keyPredicateOnEntries(keyPredicate));
    } else {
      return new FilteredKeyMultimap<>(unfiltered, keyPredicate);
    }