}

  /**
   * Returns a {@link Stream} containing the elements of the first stream, followed by the elements
   * of the second stream, and so on.
   *
   * <p>This is equivalent to {@code Stream.of(streams).flatMap(stream -> stream)}, but the returned
   * stream may perform better.
   *
   * @see Stream#concat(Stream, Stream)
   */

  }

  /**
   * Returns a {@link Stream} containing the elements of the first stream, followed by the elements
   * of the second stream, and so on.
   *
   * <p>This is equivalent to {@code Stream.of(streams).flatMap(stream -> stream)}, but the returned
   * stream may perform better.
   *
   * @see Stream#concat(Stream, Stream)
   */

   * iterator supports it.
   *
   * <p><b>{@code Stream} equivalent:</b> to concatenate an arbitrary number of streams, use {@code
   * Stream.of(stream1, stream2, ...).flatMap(s -> s)}. If the sources are iterables, use {@code
   * Stream.of(iter1, iter2, ...).flatMap(Streams::stream)}.
   *
   * @throws NullPointerException if any of the provided iterables is {@code null}
   * @since 20.0

      @Override
      Object operate(Stream<?> stream) {
        return Streams.findLast(stream);
      }
    },
    REDUCE_LAST {
      @Override
      Object operate(Stream<?> stream) {
        return stream.reduce((a, b) -> b);
      }
    },
    REDUCE_LAST_PARALLEL {
      @Override
      Object operate(Stream<?> stream) {
        return stream.parallel().reduce((a, b) -> b);
      }
    };

  }

  /**
   * Opens a new {@link Stream} for reading text one line at a time from this source. This method
   * returns a new, independent stream each time it is called.
   *
   * <p>The returned stream is lazy and only reads from the source in the terminal operation. If an
   * I/O error occurs while the stream is reading from the source or when the stream is closed, an
   * {@link UncheckedIOException} is thrown.
   *

        }
        return list.stream().map(p -> {
            final String key = p.getFirst();
            if (StringUtil.isEmpty(key) || userBean
                    .map(user -> stream(user.getRoles()).get(stream -> stream.anyMatch(s -> (ROLE_VALUE_PREFIX + s).equals(key)))
                            || stream(user.getGroups()).get(stream -> stream.anyMatch(s -> (GROUP_VALUE_PREFIX + s).equals(key))))

    assertThat(Stream.of(1).collect(toOptional())).hasValue(1);
  }

  public void testToOptionalNull() {
    Stream<@Nullable Object> stream = Stream.of((Object) null);
    assertThrows(NullPointerException.class, () -> stream.collect(toOptional()));
  }

  public void testToOptionalMultiple() {
    IllegalArgumentException expected =
        assertThrows(IllegalArgumentException.class, () -> Stream.of(1, 2).collect(toOptional()));

                final Set<String> permissionSet = new HashSet<>();
                permissionSet.add(systemHelper.getSearchRoleByUser(name));
                stream(groups).of(stream -> stream.forEach(s -> permissionSet.add(systemHelper.getSearchRoleByGroup(s))));
                stream(roles).of(stream -> stream.forEach(s -> permissionSet.add(systemHelper.getSearchRoleByRole(s))));
                permissions = permissionSet.toArray(new String[permissionSet.size()]);

   * required to be a {@link BufferedOutputStream} in order to allow implementations to simply
   * delegate to {@link #openStream()} when the stream returned by that method does not benefit from
   * additional buffering (for example, a {@code ByteArrayOutputStream}). This method returns a new,
   * independent stream each time it is called.
   *
   * <p>The caller is responsible for ensuring that the returned stream is closed.
   *

  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    Serialization.writeMultimap(this, stream);
  }

  @GwtIncompatible // java.io.ObjectInputStream
  @J2ktIncompatible
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    int keyCount = stream.readInt();
    if (keyCount < 0) {