@Override
  Iterable<Integer> createUnfiltered(Iterable<Integer> contents) {
    return Lists.newArrayList(contents);
  }

  @Override
  Iterable<Integer> filter(Iterable<Integer> elements, Predicate<? super Integer> predicate) {
    return Iterables.filter(elements, predicate);
  }

  @Override
  Collection<Integer> createUnfiltered(Iterable<Integer> contents) {
    return Lists.newArrayList(contents);
  }

  @Override
  Collection<Integer> filter(Collection<Integer> elements, Predicate<? super Integer> predicate) {
    return Collections2.filter(elements, predicate);
  }

  @Override
  Set<Integer> createUnfiltered(Iterable<Integer> contents) {
    return Sets.newHashSet(contents);
  }

  @Override
  Set<Integer> filter(Set<Integer> elements, Predicate<? super Integer> predicate) {
    return Sets.filter(elements, predicate);
  }

                  return map.entrySet().remove(o);
                }

                @Override
                public boolean removeIf(Predicate<? super Entry<String, String>> filter) {
                  return map.entrySet().removeIf(filter);
                }

                @Override
                public boolean containsAll(Collection<?> c) {
                  return map.entrySet().containsAll(c);
                }

                unfiltered.add("zzz");
                unfiltered.add("abc");
                return Collections2.filter(Collections2.filter(unfiltered, LENGTH_1), NOT_YYY_ZZZ);
              }
            })
        .named("Collections2.filter, filtered input")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,
            CollectionFeature.SUPPORTS_REMOVE,

                unfiltered.add("zzz");
                unfiltered.add("abc");
                return Collections2.filter(Collections2.filter(unfiltered, LENGTH_1), NOT_YYY_ZZZ);
              }
            })
        .named("Collections2.filter, filtered input")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,
            CollectionFeature.SUPPORTS_REMOVE,

  public void testFilter() {
    FluentIterable<String> filtered =
        FluentIterable.from(asList("foo", "bar")).filter(Predicates.equalTo("foo"));

    List<String> expected = Collections.singletonList("foo");
    List<String> actual = Lists.newArrayList(filtered);
    assertEquals(expected, actual);
    assertCanIterateAgain(filtered);
    assertEquals("[foo]", filtered.toString());
  }

  private static class TypeA {}

  }

  public void testAccept() {
    File dir = new File("foo");
    FilenameFilter filter = new PatternFilenameFilter("a+");
    assertTrue(filter.accept(dir, "a"));
    assertTrue(filter.accept(dir, "aaaa"));
    assertFalse(filter.accept(dir, "b"));

    // Show that dir is ignored
    assertTrue(filter.accept(null, "a"));
  }

  public void testNulls() throws Exception {

   *
   * <p><b>{@code Stream} equivalent:</b> {@link java.util.stream.Stream#filter Stream.filter}.
   */
  // TODO(kevinb): how can we omit that Iterables link when building gwt
  // javadoc?
  public static <E extends @Nullable Object> Collection<E> filter(
      Collection<E> unfiltered, Predicate<? super E> predicate) {
    if (unfiltered instanceof FilteredCollection) {

   * <i>not</i> needed, it may be faster to copy {@code Iterables.filter(unfiltered, predicate)} and
   * use the copy.
   *
   * <p><b>Warning:</b> {@code predicate} must be <i>consistent with equals</i>, as documented at
   * {@link Predicate#apply}. Do not provide a predicate such as {@code
   * Predicates.instanceOf(ArrayList.class)}, which is inconsistent with equals. (See {@link