List<VariantSet>与List解决方案

List<VariantSet> rsS = null;        if (pk_user == null) {            dao.setSql(getStuSql);            Map<String, String> stuParam = new HashMap<String, String>();            stuParam.put("pk_arrange", pk_arrange);            rsS = dao.queryForList(stuParam);        } else {            List listStu = new ArrayList<VariantSet>();            for (int i = 0; i < pk_user.length; i++) {                //Log.error(pk_user[i]+"====================");                listStu.add(pk_user[i]);            }            rsS = listStu;        }for (VariantSet vsS : rsS) {//此处报错。该如何修改求高手解答}