EnumSet<E> set = EnumSet.noneOf(elementType);
    Iterables.addAll(set, iterable);
    return set;
  }

  // HashSet

  /**
   * Creates a <i>mutable</i>, initially empty {@code HashSet} instance.
   *
   * <p><b>Note:</b> if mutability is not required, use {@link ImmutableSet#of()} instead. If {@code

     * ImmutableSortedMap#orderedBy}.
     */
    public Builder(Comparator<? super K> comparator) {
      this(comparator, ImmutableCollection.Builder.DEFAULT_INITIAL_CAPACITY);
    }

    private Builder(Comparator<? super K> comparator, int initialCapacity) {
      this.comparator = checkNotNull(comparator);
      this.keys = new @Nullable Object[initialCapacity];

   * avoid memory leaks when an element is no longer necessary.
   *
   * <p>This method accepts an array with element type {@code @Nullable T}, but callers must pass an
   * array whose contents are initially non-null. The {@code @Nullable} annotation indicates that
   * this method will write nulls into the array during iteration.
   *
   * <p>This is mainly just to avoid the intermediate ArrayDeque in ConsumingQueueIterator.