* accepts non-{@code Collection} iterables and empty iterables.
   */
  public static <E extends Enum<E>> EnumSet<E> newEnumSet(
      Iterable<E> iterable, Class<E> elementType) {
    EnumSet<E> set = EnumSet.noneOf(elementType);
    Iterables.addAll(set, iterable);
    return set;
  }

  // HashSet

  /**
   * Creates a <i>mutable</i>, initially empty {@code HashSet} instance.
   *

   * entries in the same order as the original iterable.
   *
   * @throws IllegalArgumentException if two keys have the same value or two values have the same
   *     key
   * @throws NullPointerException if any key, value, or entry is null
   * @since 19.0
   */
  public static <K, V> ImmutableBiMap<K, V> copyOf(
      Iterable<? extends Entry<? extends K, ? extends V>> entries) {

   * Returns an iterator that cycles indefinitely over the elements of {@code iterable}.
   *
   * <p>The returned iterator supports {@code remove()} if the provided iterator does. After {@code
   * remove()} is called, subsequent cycles omit the removed element, which is no longer in {@code
   * iterable}. The iterator's {@code hasNext()} method returns {@code true} until {@code iterable}
   * is empty.
   *

   *     original iterable.
   * @throws NullPointerException if the specified iterable is null or has any null elements.
   * @since 12.0
   */
  public static <E extends Comparable<? super E>> Collection<List<E>> orderedPermutations(
      Iterable<E> elements) {
    return orderedPermutations(elements, Ordering.natural());
  }

  /**
   * Returns a {@link Collection} of all the permutations of the specified {@link Iterable} using

  private static void runConcurrentlyMutatedTest(
      Collection<Integer> initialContents,
      Iterable<ListFrobber> actionsToPerformConcurrently,
      WrapWithIterable wrap) {
    ConcurrentlyMutatedList<Integer> concurrentlyMutatedList =
        newConcurrentlyMutatedList(initialContents, actionsToPerformConcurrently);

    Iterable<Integer> iterableToCopy =
        wrap == WrapWithIterable.WRAP

  private static void runConcurrentlyMutatedTest(
      Collection<Integer> initialContents,
      Iterable<ListFrobber> actionsToPerformConcurrently,
      WrapWithIterable wrap) {
    ConcurrentlyMutatedList<Integer> concurrentlyMutatedList =
        newConcurrentlyMutatedList(initialContents, actionsToPerformConcurrently);

    Iterable<Integer> iterableToCopy =
        wrap == WrapWithIterable.WRAP

   *     original iterable.
   * @throws NullPointerException if the specified iterable is null or has any null elements.
   * @since 12.0
   */
  public static <E extends Comparable<? super E>> Collection<List<E>> orderedPermutations(
      Iterable<E> elements) {
    return orderedPermutations(elements, Ordering.natural());
  }

  /**
   * Returns a {@link Collection} of all the permutations of the specified {@link Iterable} using

   * over keys in the order they were first encountered in the input, and the values for each key
   * are iterated in the order they were encountered.
   *
   * @throws NullPointerException if any key, value, or entry is null
   * @since 19.0
   */
  public static <K, V> ImmutableListMultimap<K, V> copyOf(
      Iterable<? extends Entry<? extends K, ? extends V>> entries) {

   * over keys in the order they were first encountered in the input, and the values for each key
   * are iterated in the order they were encountered.
   *
   * @throws NullPointerException if any key, value, or entry is null
   * @since 19.0
   */
  public static <K, V> ImmutableMultimap<K, V> copyOf(
      Iterable<? extends Entry<? extends K, ? extends V>> entries) {

    /**
     * If the specified collection is backed by an ObjectCountHashMap, it will be much more
     * efficient to iterate over it by index rather than an entry iterator, which will need to
     * allocate an object for each entry, so we check for that.
     */
    @CheckForNull
    static <T> ObjectCountHashMap<T> tryGetMap(Iterable<T> multiset) {
      if (multiset instanceof RegularImmutableMultiset) {