java String转List<Map>

String refinGrid = bgtbalanceMap.get("grid");
JSONArray proIdsJsonArr = JSONArray.fromObject(refinGrid);
List<Map> list = (List<Map>) JSONArray.toCollection(proIdsJsonArr, Map.class);
       // list中添加值
       for (Map map : list) {
            map.put("UPDATE_TIME", currentTime);
            map.put("UPDATE_USER", userCode);
        }