๋JAVA การทำ Select(Combobox) จังหวัด อำเภอ ตำบล รหัสไปรษณีย์

 txtzip.setText("");
        try {
            //int index = cmbotambon.getSelectedIndex(); //user เลือกรายการที่เท่าไหร่ของ combotype   
            //String num = bookTypeId.get(index).toString();
            String sql = "SELECT * FROM zipcode WHERE DISTRICT_ID = '" + cmbotambon.getSelectedItem() + "'";
            String url = "jdbc:mysql://localhost:3306/dbm";
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection(url, "root", "12345678");
            PreparedStatement pstm = con.prepareStatement(sql,
                      ResultSet.TYPE_SCROLL_SENSITIVE,
                      ResultSet.CONCUR_UPDATABLE);
              ResultSet rs = pstm.executeQuery();
              //bookTypeId.add(0);              
              while (rs.next()) {
//                   int tambon_id = Integer.parseInt(rs.getString("DISTRICT_ID"));                
//                String tambon_name = rs.getString("DISTRICT_NAME");
//                cmbotambon2.addItem(tambon_name);
//                cmbotambon2.setSelectedItem(tambon_id);
               txtzip.setText(rs.getString("ZIPCODE"));
              }
              pstm.close();
              con.close();
         } catch (Exception e) {
             System.out.println(e.getMessage());
         }