* duplicate in encounter order will appear in the result.
   *
   * @since 21.0
   */
  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return CollectCollectors.toImmutableSet();
  }

  /**
   * Returns the empty immutable set. Preferred over {@link Collections#emptySet} for code
   * consistency, and because the return type conveys the immutability guarantee.
   *

   * ImmutableList}, in encounter order.
   *
   * @since 21.0
   */
  public static <E> Collector<E, ?, ImmutableList<E>> toImmutableList() {
    return CollectCollectors.toImmutableList();
  }

  /**
   * Returns the empty immutable list. This list behaves and performs comparably to {@link
   * Collections#emptyList}, and is preferable mainly for consistency and maintainability of your

          java.util.function.Function<? super T, ? extends K> keyFunction,
          java.util.function.Function<? super T, ? extends V> valueFunction) {
    return CollectCollectors.toImmutableEnumMap(keyFunction, valueFunction);
  }

  /**
   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys