}
    };
  }

  @Override
  public Optional<V> edgeValue(N nodeU, N nodeV) {
    return Optional.ofNullable(edgeValueOrDefault(nodeU, nodeV, null));
  }

  @Override
  public Optional<V> edgeValue(EndpointPair<N> endpoints) {
    return Optional.ofNullable(edgeValueOrDefault(endpoints, null));
  }

  @Override
  public final boolean equals(@CheckForNull Object obj) {

   * reference; otherwise returns {@link Optional#absent}.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this method is equivalent to Java 8's
   * {@code Optional.ofNullable}.
   */
  public static <T> Optional<T> fromNullable(@CheckForNull T nullableReference) {
    return (nullableReference == null) ? Optional.<T>absent() : new Present<T>(nullableReference);
  }

  /**

          throw multiples(true);
        }
        return this;
      }
    }

    Optional<Object> getOptional() {
      if (extras.isEmpty()) {
        return Optional.ofNullable(element);
      } else {
        throw multiples(false);
      }
    }

    Object getElement() {
      if (element == null) {
        throw new NoSuchElementException();

   * reference; otherwise returns {@link Optional#absent}.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this method is equivalent to Java 8's
   * {@code Optional.ofNullable}.
   */
  public static <T> Optional<T> fromNullable(@CheckForNull T nullableReference) {
    return (nullableReference == null) ? Optional.<T>absent() : new Present<T>(nullableReference);
  }

  Optional() {}

      }
    }

    @IgnoreJRERequirement // see enclosing class (whose annotation Animal Sniffer ignores here...)
    Optional<Object> getOptional() {
      if (extras.isEmpty()) {
        return Optional.ofNullable(element);
      } else {
        throw multiples(false);
      }
    }

    Object getElement() {
      if (element == null) {
        throw new NoSuchElementException();

        return incidentNodes(edge).adjacentNode(nodePresent).equals(nodeToCheck);
      }
    };
  }

  @Override
  public Optional<E> edgeConnecting(N nodeU, N nodeV) {
    return Optional.ofNullable(edgeConnectingOrNull(nodeU, nodeV));
  }

  @Override
  public Optional<E> edgeConnecting(EndpointPair<N> endpoints) {
    validateEndpoints(endpoints);