private abstract static class AnAbstractClass {
    @SuppressWarnings("unused")
    public AnAbstractClass(String s) {}

    @SuppressWarnings("unused")
    public void failsToCheckNull(String s) {}
  }

  private static class NoPublicStaticMethods {
    @SuppressWarnings("unused") // To test non-public factory isn't used.
    static String notPublic() {
      return "";
    }