class App {

  /**
   * Program entry point.
   *
   * @param args command line args
   */
  public static void main(String[] args) {<FILL_FUNCTION_BODY>}
}

    var user = new User("user", 24, Sex.FEMALE, "foobar.com");
    LOGGER.info(Validator.of(user).validate(User::name, Objects::nonNull, "name is null")
        .validate(User::name, name -> !name.isEmpty(), "name is empty")
        .validate(User::email, email -> !email.contains("@"), "email doesn't contains '@'")
        .validate(User::age, age -> age > 20 && age < 30, "age isn't between...").get()
        .toString());
  
<no_super_class>