private String vendorCode;
    private VendorType sth;
    private String sth;
    private String sth;
    private String sth;
    private String sth;
    private String sth;
    private String sth;

public ResponseEntity<?> restSaveVendors(@RequestBody sth sthConfiguration)
      {

        Optional<sthEntity> sthEntity = sthRepository.findBysthCode(sthConfiguration.getsth().getsthCode());

        if(sthEntity.isPresent())
        {
            return new ResponseEntity<>(HttpStatus.BAD_REQUEST);
        }


    so my code is below; I think is wrong

                if(sthEntity != null)
                {
                    sthRepository.save(sthConfiguration.getsth());
                }