code: @Override
      public boolean isSet(String propName) {
          if (propName.equals(PROP_PRINCIPAL_NAME)) {
              return isSetPrincipalName();
          }
          if (propName.equals(PROP_PASSWORD)) {
              return isSetPassword();
          }
          if (propName.equals(PROP_REALM)) {
              return isSetRealm();
          }
          if (propName.equals(PROP_CERTIFICATE)) {
              return isSetCertificate();
          }
          return super.isSet(propName);
      }
docs: Returns true if the requested property is set; false, otherwise.
  
  @return
  returned object is {@link boolean }