* contained references are {@linkplain Object#equals equal} to each other or both are absent.
   * Note that {@code Optional} instances of differing parameterized types can be equal.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> no differences.
   */
  @Override
  public abstract boolean equals(@CheckForNull Object object);

  /**

 * @author Louis Wasserman
 */
@GwtIncompatible // unnecessary
@ElementTypesAreNonnullByDefault
class ImmutableMapEntry<K, V> extends ImmutableEntry<K, V> {
  /**
   * Creates an {@code ImmutableMapEntry} array to hold parameterized entries. The result must never
   * be upcast back to ImmutableMapEntry[] (or Object[], etc.), or allowed to escape the class.
   *

    LinkedHashMultimap<String, Integer> multimap = LinkedHashMultimap.create();
    for (int z = 1; z <= 100; z++) {
      multimap.put("a", z);
      // The Eclipse compiler (and hence GWT) rejects a parameterized cast.
      @SuppressWarnings("unchecked")
      LinkedHashMultimap<String, Integer>.ValueSet valueSet =
          (LinkedHashMultimap.ValueSet) multimap.backingMap().get("a");
      assertEquals(z, valueSet.size());

        return constructor.newInstance(args);
      } catch (InstantiationException e) {
        throw new RuntimeException(constructor + " failed.", e);
      }
    }

    /**
     * If the class is parameterized, such as {@link java.util.ArrayList ArrayList}, this returns
     * {@code ArrayList<E>}.
     */
    @Override
    Type getGenericReturnType() {
      Class<?> declaringClass = getDeclaringClass();