Checking Resulset contain Null records in mysql Query using Java

 String FPS_Qry = "Select length from tbl_dataset ";

ResultSet rstt = db.stmt9.executeQuery(FPS_Qry);
                String FPS = "";
                if (!rstt.wasNull()) {

                    while (rstt.next()) {

                        if (rstt.getString(1) != null) {
                            FPS = rstt.getString(1);
                        }
                    }
                }