Set<String> unfiltered = Sets.newLinkedHashSet();
                unfiltered.add("yyy");
                unfiltered.addAll(ImmutableList.copyOf(elements));
                unfiltered.add("zzz");
                unfiltered.add("abc");
                return Sets.filter(
                    Sets.filter(unfiltered, Collections2Test.LENGTH_1),

    extends FilteredEntryMultimap<K, V> implements FilteredSetMultimap<K, V> {

  FilteredEntrySetMultimap(SetMultimap<K, V> unfiltered, Predicate<? super Entry<K, V>> predicate) {
    super(unfiltered, predicate);
  }

  @Override
  public SetMultimap<K, V> unfiltered() {
    return (SetMultimap<K, V>) unfiltered;
  }

  @Override
  public Set<V> get(@ParametricNullness K key) {
    return (Set<V>) super.get(key);
  }

    extends FilteredKeyMultimap<K, V> implements ListMultimap<K, V> {
  FilteredKeyListMultimap(ListMultimap<K, V> unfiltered, Predicate<? super K> keyPredicate) {
    super(unfiltered, keyPredicate);
  }

  @Override
  public ListMultimap<K, V> unfiltered() {
    return (ListMultimap<K, V>) super.unfiltered();
  }

  @Override
  public List<V> get(@ParametricNullness K key) {
    return (List<V>) super.get(key);
  }

    extends FilteredKeyMultimap<K, V> implements FilteredSetMultimap<K, V> {

  FilteredKeySetMultimap(SetMultimap<K, V> unfiltered, Predicate<? super K> keyPredicate) {
    super(unfiltered, keyPredicate);
  }

  @Override
  public SetMultimap<K, V> unfiltered() {
    return (SetMultimap<K, V>) unfiltered;
  }

  @Override
  public Set<V> get(@ParametricNullness K key) {
    return (Set<V>) super.get(key);
  }

    return Iterables.removeIf(
        multimap.unfiltered().entries(),
        // explicit <Entry<K, V>> is required to build with JDK6
        Predicates.<Entry<K, V>>and(
            multimap.entryPredicate(), Maps.<V>valuePredicateOnEntries(Predicates.in(c))));
  }

  @Override
  public boolean retainAll(Collection<?> c) {
    return Iterables.removeIf(
        multimap.unfiltered().entries(),

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * An interface for all filtered multimap types.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
interface FilteredMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends Multimap<K, V> {
  Multimap<K, V> unfiltered();

  Predicate<? super Entry<K, V>> entryPredicate();

    List<String> expected = emptyList();
    List<String> actual = Lists.newArrayList(filtered);
    assertEquals(expected, actual);
  }

  public void testFilterMatchAll() {
    Iterator<String> unfiltered = Lists.newArrayList("foo", "bar").iterator();
    Iterator<String> filtered = filter(unfiltered, Predicates.alwaysTrue());

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * An interface for all filtered multimap types.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
interface FilteredMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends Multimap<K, V> {
  Multimap<K, V> unfiltered();

  Predicate<? super Entry<K, V>> entryPredicate();

    checkNotNull(retainIfTrue);
    return new FluentIterable<T>() {
      @Override
      public Iterator<T> iterator() {
        return Iterators.filter(unfiltered.iterator(), retainIfTrue);
      }
    };
  }

  /**
   * Returns a view of {@code unfiltered} containing all elements that are of the type {@code
   * desiredType}. The returned iterable's iterator does not support {@code remove()}.
   *

    List<String> expected = emptyList();
    List<String> actual = Lists.newArrayList(filtered);
    assertEquals(expected, actual);
  }

  public void testFilterMatchAll() {
    Iterator<String> unfiltered = Lists.newArrayList("foo", "bar").iterator();
    Iterator<String> filtered = filter(unfiltered, Predicates.alwaysTrue());