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

  /**
   * @since 10.0 (previously, subclasses would override equivalent())
   */
  @ForOverride
  protected abstract boolean doEquivalent(T a, T b);

  /**
   * <i>May</i> return {@code true} if {@code object} is a {@code Equivalence} that behaves

  }

  public void testSetKeyEquivalence() {
    Equivalence<Object> testEquivalence =
        new Equivalence<Object>() {
          @Override
          protected boolean doEquivalent(Object a, Object b) {
            return false;
          }

          @Override
          protected int doHash(Object t) {
            return 0;
          }
        };

  }

  public void testSetKeyEquivalence() {
    Equivalence<Object> testEquivalence =
        new Equivalence<Object>() {
          @Override
          protected boolean doEquivalent(Object a, Object b) {
            return false;
          }

          @Override
          protected int doHash(Object t) {
            return 0;
          }
        };

  }

  public void testSetKeyEquivalence() {
    Equivalence<Object> testEquivalence =
        new Equivalence<Object>() {
          @Override
          protected boolean doEquivalent(Object a, Object b) {
            return false;
          }

          @Override
          protected int doHash(Object t) {
            return 0;
          }
        };

  }

  public void testSetKeyEquivalence() {
    Equivalence<Object> testEquivalence =
        new Equivalence<Object>() {
          @Override
          protected boolean doEquivalent(Object a, Object b) {
            return false;
          }

          @Override
          protected int doHash(Object t) {
            return 0;
          }
        };