* <p><b>{@code Stream} equivalent:</b> {@link Stream#filter}.
   */
  public static <T extends @Nullable Object> Iterable<T> filter(
      final Iterable<T> unfiltered, final Predicate<? super T> retainIfTrue) {
    checkNotNull(unfiltered);
    checkNotNull(retainIfTrue);
    return new FluentIterable<T>() {
      @Override
      public Iterator<T> iterator() {
        return Iterators.filter(unfiltered.iterator(), retainIfTrue);
      }

                    Map<String, String> map = Maps.newHashMap();
                    putEntries(map, entries);
                    map.putAll(ENTRIES_TO_FILTER);
                    map = Maps.filterEntries(map, FILTER_ENTRIES_1);
                    return Maps.filterEntries(map, FILTER_ENTRIES_2);
                  }
                })
            .named("Maps.filterEntries[Maps.filterEntries[Map, Predicate], Predicate]")

   */
  // 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.

      RegularImmutableMap<K, V> empty = (RegularImmutableMap<K, V>) EMPTY;
      return empty;
    } else if (n == 1) {
      // requireNonNull is safe because the first `2*n` elements have been filled in.
      checkEntryNotNull(
          requireNonNull(alternatingKeysAndValues[0]), requireNonNull(alternatingKeysAndValues[1]));
      return new RegularImmutableMap<K, V>(null, alternatingKeysAndValues, 1);
    }

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

                  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);
                }

      if (isSatisfied(guard)) {
        guard.condition.signal();
        break;
      }
    }
  }

  /**
   * Exactly like signalNextWaiter, but caller guarantees that guardToSkip need not be considered,
   * because caller has previously checked that guardToSkip.isSatisfied() returned false. An
   * optimization for the case that guardToSkip.isSatisfied() may be expensive.
   *

              // We can't check that the key is mightContain() == false before the
              // put() because the key could have already been generated *or* the
              // bloom filter might say true even when it's not there (false
              // positive).
              bloomFilter.put(key);
              // False negative should *never* happen.

            .and(Equivalence.equals());
    ImmutableListMultimap<Character, Character> empty = ImmutableListMultimap.of();
    ImmutableListMultimap<Character, Character> filled =
        ImmutableListMultimap.<Character, Character>builder()
            .putAll('b', Arrays.asList('a', 'n', 'a', 'n', 'a'))
            .putAll('a', Arrays.asList('p', 'p', 'l', 'e'))

 *
 * <p><b>Note:</b> {@code ComparisonChain} instances are <b>immutable</b>. For this utility to work
 * correctly, calls must be chained as illustrated above.
 *
 * <p>Performance note: Even though the {@code ComparisonChain} caller always invokes its {@code
 * compare} methods unconditionally, the {@code ComparisonChain} implementation stops calling its
 * inputs' {@link Comparable#compareTo compareTo} and {@link Comparator#compare compare} methods as