if (a == b) {
      return true;
    }
    if (a == null || b == null) {
      return false;
    }
    return doEquivalent(a, b);
  }

  /**
   * @deprecated Provided only to satisfy the {@link BiPredicate} interface; use {@link #equivalent}
   *     instead.
   * @since 21.0
   */
  @Deprecated
  @Override
  public final boolean test(@CheckForNull T t, @CheckForNull T u) {

   *
   * <p>The {@code hash} has the following properties:
   *
   * <ul>
   *   <li>It is <i>consistent</i>: for any reference {@code x}, multiple invocations of {@code
   *       hash(x}} consistently return the same value provided {@code x} remains unchanged
   *       according to the definition of the equivalence. The hash need not remain consistent from
   *       one execution of an application to another execution of the same application.