assertFalse(filter(createUnfiltered(contents), EVEN).contains(new Object()));
      }
    }

    public void testAddAllFailsAtomically() {
      ImmutableList<Integer> toAdd = ImmutableList.of(2, 4, 3);
      for (List<Integer> contents : SAMPLE_INPUTS) {
        C filtered = filter(createUnfiltered(contents), EVEN);
        C filteredToModify = filter(createUnfiltered(contents), EVEN);

   * it does.
   *
   * <p>The caller is responsible for ensuring that the returned stream is closed. For example:
   *
   * <pre>{@code
   * try (Stream<String> lines = source.lines()) {
   *   lines.map(...)
   *      .filter(...)
   *      .forEach(...);
   * }
   * }</pre>
   *

        @SuppressWarnings("unchecked")
        Entry<String, Integer> entry = (Entry<String, Integer>) o;
        multimap.put(entry.getKey(), entry.getValue());
      }
      return filter(multimap);
    }

    abstract ListMultimap<String, Integer> filter(ListMultimap<String, Integer> multimap);

    @Override
    public Collection<Integer> createCollection(Iterable<? extends Integer> values) {
      return Lists.newArrayList(values);

 * relevant methods below.
 *
 * <ul>
 *   <li>This class is serializable; {@code java.util.Optional} is not.
 *   <li>{@code java.util.Optional} has the additional methods {@code ifPresent}, {@code filter},
 *       {@code flatMap}, and {@code orElseThrow}.
 *   <li>{@code java.util} offers the primitive-specialized versions {@code OptionalInt}, {@code

        @SuppressWarnings("unchecked")
        Entry<String, Integer> entry = (Entry<String, Integer>) o;
        multimap.put(entry.getKey(), entry.getValue());
      }
      return filter(multimap);
    }

    abstract ListMultimap<String, Integer> filter(ListMultimap<String, Integer> multimap);

    @Override
    public Collection<Integer> createCollection(Iterable<? extends Integer> values) {
      return Lists.newArrayList(values);

      return emptySet();
    } else {
      return emptyList();
    }
  }

  @Override
  public void clear() {
    keySet().clear();
  }

  @Override
  Set<K> createKeySet() {
    return Sets.filter(unfiltered.keySet(), keyPredicate);
  }

  @Override
  public Collection<V> get(@ParametricNullness K key) {
    if (keyPredicate.apply(key)) {
      return unfiltered.get(key);

                unfiltered.add("zzz");
                unfiltered.add("abc");
                return Sets.filter(
                    Sets.filter(unfiltered, Collections2Test.LENGTH_1),
                    Collections2Test.NOT_YYY_ZZZ);
              }
            })
        .named("Sets.filter, filtered input")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,

 *
 * <p>{@code CharSink} provides two kinds of methods:
 *
 * <ul>
 *   <li><b>Methods that return a writer:</b> These methods should return a <i>new</i>, independent
 *       instance each time they are called. The caller is responsible for ensuring that the
 *       returned writer is closed.
 *   <li><b>Convenience methods:</b> These are implementations of common operations that are

  }

  interface X {}

  interface Y {}

  static class A implements X, Y {}

  static class B implements X, Y {}

  /**
   * This test passes if the {@code concat(…).filter(…).filter(…)} statement at the end compiles.
   * That statement compiles only if {@link FluentIterable#concat concat(aIterable, bIterable)}
   * returns a {@link FluentIterable} of elements of an anonymous type whose supertypes are the <a

   * elements than the collection), the element in the array immediately following the end of the
   * collection is set to {@code null}. This is useful in determining the length of the collection
   * <i>only</i> if the caller knows that the collection does not contain any null elements.
   *
   * <p>This method returns the elements in the order they are returned by the collection's
   * iterator.
   *