典型用法--PreparedStatement

 1 String sql2 = "select monid from monindex where groupname = ?";
 2         try {
 3             PreparedStatement pre1 = conn.prepareStatement(sql2);
 4             Iterator<String> it = groupnames.iterator();
 5             while (it.hasNext()) {
 6                 HashSet<String> monids = new HashSet<String>();
 7                 String gname = it.next();
 8                 pre1.setString(1, gname);
 9                 ResultSet rs = pre1.executeQuery();
10                 while (rs.next()) {
11                     monids.add(rs.getString(1));
12                 }
13                 groupcomein(gname, monids, day, begin, end);
14                 logger.info("insert group " + gname + " data into DB");
15             }
16         } catch (SQLException e) {
17             e.printStackTrace();
18         }