问不能强制转换为java.base/java.util.Optional

EN

    @PostMapping("request")
    public ResponseEntity<?> resetRequest(@RequestBody PasswordResetDTO resetDTO) {
        return userRepository.findByUsername(resetDTO.getName()).map(user -> {

            if (!user.getEmail().equals(resetDTO.getEmail())) {
                return new ResponseEntity<>("NAME_AND_EMAIL_MISMATCH", HttpStatus.BAD_REQUEST);
            }

            resetHandler.sendResetMail(user);

            return ok(resetDTO);
        })
                .orElseGet(() -> notFound().build());
    }

public interface UserRepository extends CrudRepository<Users, Integer> {
    Optional<Users> findByUsername(String username);

    Optional<Users> findByEmail(String email);

    Optional<Users> findByResetCode(String code);
}

    @Override
    public Optional<Users> findByUsername(String username) {
        String hql = "select e from " + Users.class.getName() + " e where e.login = ?";
        Query query = entityManager.createQuery(hql).setParameter(0, username);
        Optional<Users> users = (Optional<Users>) query.getSingleResult();
        return users;
    }