return o == this || o == null;
    }

    @Override
    public int hashCode() {
      return 0;
    }
  }

  /** Test class that returns true even if the test object is of the wrong class */
  private static class InvalidEqualsIncompatibleClassObject {

    @Override
    public boolean equals(@Nullable Object o) {
      return o != null;
    }

    @Override

      return o == this || o == null;
    }

    @Override
    public int hashCode() {
      return 0;
    }
  }

  /** Test class that returns true even if the test object is of the wrong class */
  private static class InvalidEqualsIncompatibleClassObject {

    @Override
    public boolean equals(@Nullable Object o) {
      return o != null;
    }

    @Override