*
 * <p>An instance of this class is serializable if its reference is absent or is a serializable
 * object.
 *
 * <p><b>Comparison to {@code java.util.Optional} (JDK 8 and higher):</b> A new {@code Optional}
 * class was added for Java 8. The two classes are extremely similar, but incompatible (they cannot
 * share a common supertype). <i>All</i> known differences are listed either here or with the

    assertThat(stream(FluentIterable.of(1, 2, 3)).filter(n -> n > 1)).containsExactly(2, 3);
  }

  @SuppressWarnings("deprecation")
  public void testStream_collection() {
    assertThat(stream(Arrays.asList())).isEmpty();
    assertThat(stream(Arrays.asList("a"))).containsExactly("a");
    assertThat(stream(Arrays.asList(1, 2, 3)).filter(n -> n > 1)).containsExactly(2, 3);
  }

   */
  // 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) {
      // Support clear(), removeAll(), and retainAll() when filtering a filtered
      // collection.

   * java.util.stream.Stream#filter}. This method is not being deprecated, but we gently encourage
   * you to migrate to streams.
   */
  // TODO(kevinb): how to omit that last sentence when building GWT javadoc?
  public static <E extends @Nullable Object> Set<E> filter(
      Set<E> unfiltered, Predicate<? super E> predicate) {
    if (unfiltered instanceof SortedSet) {
      return filter((SortedSet<E>) unfiltered, predicate);

  private static class HasBoth extends TypeA implements TypeB {}

  @GwtIncompatible // Iterables.filter(Iterable, Class)
  public void testFilterByType_iterator() throws Exception {
    HasBoth hasBoth = new HasBoth();
    Iterable<TypeA> alist = Lists.newArrayList(new TypeA(), new TypeA(), hasBoth, new TypeA());
    Iterable<TypeB> blist = Iterables.filter(alist, TypeB.class);
    assertThat(blist).containsExactly(hasBoth).inOrder();
  }

   * underlying multimap.
   *
   * <p>The returned multimap isn't threadsafe or serializable, even if {@code unfiltered} is.
   *
   * <p>Many of the filtered multimap's methods, such as {@code size()}, iterate across every
   * key/value mapping in the underlying multimap and determine which satisfy the filter. When a

    Enumeration<Integer> enumer = enumerate(1, 2, 3);
    Iterator<Integer> iter = Iterators.forEnumeration(enumer);

    assertTrue(iter.hasNext());
    assertEquals(1, (int) iter.next());
    assertTrue(iter.hasNext());
    assertEquals(2, (int) iter.next());
    assertTrue(iter.hasNext());
    assertEquals(3, (int) iter.next());
    assertFalse(iter.hasNext());
  }

  public void testAsEnumerationEmpty() {

  private static class HasBoth extends TypeA implements TypeB {}

  @GwtIncompatible // Iterables.filter(Iterable, Class)
  public void testFilterByType_iterator() throws Exception {
    HasBoth hasBoth = new HasBoth();
    Iterable<TypeA> alist = Lists.newArrayList(new TypeA(), new TypeA(), hasBoth, new TypeA());
    Iterable<TypeB> blist = Iterables.filter(alist, TypeB.class);
    assertThat(blist).containsExactly(hasBoth).inOrder();
  }

          <configuration>
            <includes>
              <include>${test.include}</include>
            </includes>
            <!-- By having our own entries here, we also override the default exclusion filter, which excludes all nested classes. -->
            <excludes>
              <!-- https://github.com/google/guava/issues/2840 -->
              <exclude>%regex[.*PackageSanityTests.*.class]</exclude>

  }

  /**
   * Combines this Bloom filter with another Bloom filter by performing a bitwise OR of the
   * underlying data. The mutations happen to <b>this</b> instance. Callers must ensure the Bloom
   * filters are appropriately sized to avoid saturating them.
   *
   * @param that The Bloom filter to combine this Bloom filter with. It is not mutated.