unfiltered.put("foo", 55556);
    unfiltered.put("badkey", 1);
    unfiltered.put("foo", 1);
    Multimap<String, Integer> keyFiltered = Multimaps.filterKeys(unfiltered, KEY_PREDICATE);
    Multimap<String, Integer> filtered = Multimaps.filterValues(keyFiltered, VALUE_PREDICATE);
    assertEquals(1, filtered.size());
    assertTrue(filtered.containsEntry("foo", 1));

    final Collection<E> unfiltered;
    final Predicate<? super E> predicate;

    FilteredCollection(Collection<E> unfiltered, Predicate<? super E> predicate) {
      this.unfiltered = unfiltered;
      this.predicate = predicate;
    }

    FilteredCollection<E> createCombined(Predicate<? super E> newPredicate) {
      return new FilteredCollection<>(unfiltered, Predicates.and(predicate, newPredicate));
    }

    assertEquals(ImmutableMap.of("two", 2, "four", 4), filtered);

    filtered.clear();
    assertEquals(ImmutableMap.of("one", 1, "three", 3), unfiltered);
    assertTrue(filtered.isEmpty());
  }

  public void testFilteredEntriesIllegalPut() {
    Map<String, Integer> unfiltered = createUnfiltered();
    unfiltered.put("cat", 3);
    unfiltered.put("dog", 2);
    unfiltered.put("horse", 5);

    assertEquals(ImmutableMap.of("two", 2, "four", 4), filtered);

    filtered.clear();
    assertEquals(ImmutableMap.of("one", 1, "three", 3), unfiltered);
    assertTrue(filtered.isEmpty());
  }

  public void testFilteredEntriesIllegalPut() {
    Map<String, Integer> unfiltered = createUnfiltered();
    unfiltered.put("cat", 3);
    unfiltered.put("dog", 2);
    unfiltered.put("horse", 5);

    }
    return new FilteredMultiset<>(unfiltered, predicate);
  }

  private static final class FilteredMultiset<E extends @Nullable Object> extends ViewMultiset<E> {
    final Multiset<E> unfiltered;
    final Predicate<? super E> predicate;

    FilteredMultiset(Multiset<E> unfiltered, Predicate<? super E> predicate) {
      this.unfiltered = checkNotNull(unfiltered);

    unfiltered.put("foo", 55556);
    unfiltered.put("badkey", 1);
    unfiltered.put("foo", 1);
    Multimap<String, Integer> keyFiltered = Multimaps.filterKeys(unfiltered, KEY_PREDICATE);
    Multimap<String, Integer> filtered = Multimaps.filterValues(keyFiltered, VALUE_PREDICATE);
    assertEquals(1, filtered.size());
    assertTrue(filtered.containsEntry("foo", 1));

                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),

    SortedMap<String, Integer> unfiltered = createUnfiltered();
    unfiltered.put("apple", 2);
    unfiltered.put("banana", 6);
    unfiltered.put("cat", 3);
    unfiltered.put("dog", 5);

    SortedMap<String, Integer> filtered = Maps.filterEntries(unfiltered, CORRECT_LENGTH);
    assertEquals("banana", filtered.firstKey());
    assertEquals("cat", filtered.lastKey());
  }

      Multimap<K, V> unfiltered, final Predicate<? super K> keyPredicate) {
    if (unfiltered instanceof SetMultimap) {
      return filterKeys((SetMultimap<K, V>) unfiltered, keyPredicate);
    } else if (unfiltered instanceof ListMultimap) {
      return filterKeys((ListMultimap<K, V>) unfiltered, keyPredicate);
    } else if (unfiltered instanceof FilteredKeyMultimap) {

    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(),