code: public T fetchSingle() throws InstantiationException, IllegalAccessException, SQLException {
          if (!finished) {
              T result = primitive ? fetchSinglePrimitiveInternal() : fetchSingleInternal();
              next();
              return result;
          } else {
              throw new SQLException("Result set don't have data for single fetch.");
          }
      }
docs: Fetches single entity, being sure that it exists. Throws exception if there is no entity.
  
  @return Single entity.
  @throws InstantiationException
  @throws IllegalAccessException
  @throws SQLException