Spring: You should not mix @transactional with synchronized

NaiveJavaSynchronizedATMService.java

@Service
public class NaiveJavaSynchronizedATMService {

    @Autowired
    private AccountRepository repository;

    @Transactional
    public synchronized void withdraw(Long accountId, double amount) {

        Account account = repository.findById(accountId).orElseThrow(() -> {
            throw new IllegalStateException("account does not exist: " + accountId);
        });

        double newBalance = (account.getBalance() - amount);
        if (newBalance < 0) {
            throw new IllegalStateException("there's not enough balance");
        }

        account.setBalance(newBalance);
    }
}

NaiveJavaSynchronizedATMServiceTest.java

class NaiveJavaSynchronizedATMServiceTest extends SpringBootIntegrationTest {

    @Autowired
    private AccountRepository accountRepository;
    @Autowired
    private TransactionRepository transactionRepository;

    @Autowired
    private NaiveJavaSynchronizedATMService naiveJavaSynchronizedATMService;

    private Account ACCOUNT;

    @BeforeEach
    public void setUp() {
        transactionRepository.deleteAll();
        accountRepository.deleteAll();
        this.ACCOUNT = accountRepository
                .save(new Account("Jordi", 100.0));
    }

    @Test
    @DisplayName("should withdraw money from account concurrently")
    public void t2() throws InterruptedException {

        doSyncAndConcurrently(10, s -> {
            naiveJavaSynchronizedATMService
                    .withdraw(ACCOUNT.getId(), 20.0);
        });

        assertAll("account and transaction states",
            () -> assertEquals(0.0, accountRepository.getBalance(ACCOUNT.getId()), "account balance"),
            () -> assertEquals(5, transactionRepository.countByAccount(ACCOUNT), "number of transactions")
        );
    }

}

is the doSyncAndConcurrently from a lib?