I’m studying clean architecture building a simple Spring Boot application.

Some of my classes are:

public class EClient implements Serializable, EClienteInterface {...}

public interface ClientRepository extends JpaRepository<EClient, String> {...}

And finnaly, the reason of my question:

@Override
public Optional<EClientInterface> findClient(String cpf) {
    return repository.findById(cpf).map(eClient -> eClient);
}

Basically, I was forced to put a .map(eClient -> eClient), because my error message was:

• Required -> Optional<EClientInterface>
• Provided -> Optional<EClient>

To sum up, my questions are:

1. Why do I need the .map? Is it because Optinal only accpets the exact type and not implementations or subclasses?

2. Why does this map actually works? It looks redundant to me