*/
  // 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.

   * 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

   * <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);
      }

  }

  private static Type[] toArray(Collection<Type> types) {
    return types.toArray(new Type[0]);
  }

  private static Iterable<Type> filterUpperBounds(Iterable<Type> bounds) {
    return Iterables.filter(bounds, Predicates.not(Predicates.<Type>equalTo(Object.class)));
  }

  private static void disallowPrimitiveType(Type[] types, String usedAs) {
    for (Type type : types) {
      if (type instanceof Class) {

    return CollectSpliterators.indexed(size(), SPLITERATOR_CHARACTERISTICS, this::get);
  }

  @Override
  int copyIntoArray(@Nullable Object[] dst, int offset) {
    // this loop is faster for RandomAccess instances, which ImmutableLists are
    int size = size();
    for (int i = 0; i < size; i++) {
      dst[offset + i] = get(i);
    }
    return offset + size;
  }

  /**

    return CollectCollectors.toImmutableSortedMap(
        comparator, keyFunction, valueFunction, mergeFunction);
  }

  /*
   * TODO(kevinb): Confirm that ImmutableSortedMap is faster to construct and
   * uses less memory than TreeMap; then say so in the class Javadoc.
   */
  private static final Comparator<?> NATURAL_ORDER = Ordering.natural();

 * 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

@ElementTypesAreNonnullByDefault
public abstract class AbstractFuture<V extends @Nullable Object> extends InternalFutureFailureAccess
    implements ListenableFuture<V> {
  // NOTE: Whenever both tests are cheap and functional, it's faster to use &, | instead of &&, ||

  static final boolean GENERATE_CANCELLATION_CAUSES;

  static {
    // System.getProperty may throw if the security policy does not permit access.
    boolean generateCancellationCauses;

   */
  // 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);