public List<ClassObj> getClassTable(PreparedStatement pre) {
        List<ClassObj> items = new LinkedList<ClassObj>();
        try {
            ResultSet rs = pre.executeQuery();
            if (rs != null) {
                while (rs.next()) {
                    ClassObj item = new ClassObj();
                    item.setClassname(rs.getString("classname"));
                    item.setStaffId(rs.getString("staff_id"));
                    item.setObjId(rs.getInt("obj_id"));
                    items.add(item);
                }
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return items;
    }