@Override
    @Transactional
    public OgrenciCommand saveOgrenciCommand(OgrenciCommand command) {
        Optional<Okul> okulOptional = okulRepository.findById(command.getOkulId());

        if(!okulOptional.isPresent()){

            //todo toss error if not found!
            log.error("Okul not found for id: " + command.getOkulId());
            return new OgrenciCommand();
        } else {
            Okul okul = okulOptional.get();

            Optional<Ogrenci> OgrenciOptional = okul
                    .getOgrenciler()
                    .stream()
                    .filter(Ogrenci -> Ogrenci.getId().equals(command.getId()))
                    .findFirst();

            if(OgrenciOptional.isPresent()){
                Ogrenci OgrenciFound = OgrenciOptional.get();
                OgrenciFound.setIsim(command.getIsim());
                OgrenciFound.setSoyisim(command.getSoyisim());
                OgrenciFound.setOgrenimDerecesi(ogrenimDerecesiRepository
                        .findById(command.getOgrenimDerecesi().getId())
                        .orElseThrow(() -> new RuntimeException("Ogrenim derecesi bulunamadi"))); 
            } else {
                //add new Ogrenci
                okul.addOgrenci(OgrenciCommandToOgrenci.convert(command));
            }

            Okul savedOkul = okulRepository.save(okul);

            //todo check for fail
            return OgrenciToOgrenciCommand.convert(savedOkul.getOgrenciler().stream()
                    .filter(okulOgrenciler -> okulOgrenciler.getId().equals(command.getId()))
                    .findFirst()
                    .get());
        }

    }

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 phpmyadmin : Depends: php-mysql but it is not going to be installed or
                       php-mysqli or
                       php-mysqlnd
              Recommends: php-gd
E: Unable to correct problems, you have held broken packages.

 public interface EmployeeDao(){
 }
 public class EmployeeDaoImp implements EmployeeDao (){ }

 public interface CompanyDao(){ }
 public class CompanyDaoImp implements CompanyDao (){ }