code: public int update (Connection conn, T obj)
          throws SQLException
      {
          return update(conn, obj, null);
      }
docs: Update record in the table using table's primary key to locate record in
  the table and values of fields of specified object <I>obj</I> to alter
  record fields.
  
  @param obj object specifying value of primary key and new values of
  updated record fields
  
  @return number of objects actually updated