Java swing 的下拉选择框的监听有什么问题吗，为什么程序没有反应

package test;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.sql.*;
import java.util.LinkedList;

public class inquiryAddress extends JDialog {
    //省，市县下拉选择框
    JComboBox province =new JComboBox();
    JComboBox city=new JComboBox();
    JComboBox county=new JComboBox();
    Box box1=Box.createHorizontalBox();
    //确定地址信息
    JButton ok=new JButton();
    Dimension d=new Dimension(20,13);
    Dimension dd=new Dimension(60,40);
    Box box2=Box.createHorizontalBox();
    //组装所有按键
    Box box=Box.createVerticalBox();

   LinkedList inquiry(String name) throws SQLException {  //得到所有省信息
       //获取地址信息
        Connection conn = null;PreparedStatement ps=null; ResultSet rs=null;
        LinkedList list=new LinkedList();
        //从MySQL中读取表格内容
        conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/farmer", "root", "123456");
        //获取执行mysql语句的执行对象
        ps= conn.prepareStatement("select name from province ;");
       // ps.setString(1,name);
        rs=ps.executeQuery();
        while (rs.next()) {
            list.add(rs.getString("name"));
        }
        return list;
    }
    LinkedList inquiry2(String type) throws SQLException {
        //获取地址信息
        Connection conn = null;PreparedStatement ps=null; ResultSet rs=null;
        LinkedList list=new LinkedList();
        //从MySQL中读取表格内容
        conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/farmer", "root", "123456");
        //获取执行mysql语句的执行对象
        ps= conn.prepareStatement("select name from city where parent_code_id = (select no from poverty where name=?) ;");
        ps.setString(1,type);
        rs=ps.executeQuery();
        while (rs.next()) {
            list.add(rs.getString("name"));
        }
        return list;
    }
    LinkedList inquiry3(String type) throws SQLException {
        //获取地址信息
        Connection conn = null;PreparedStatement ps=null; ResultSet rs=null;
        LinkedList list=new LinkedList();
        //从MySQL中读取表格内容
        conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/farmer", "root", "123456");
        //获取执行mysql语句的执行对象
        ps= conn.prepareStatement("select name from county where parent_code_id = (select no from city where name=?) ;");
        ps.setString(1,type);
        rs=ps.executeQuery();
        while (rs.next()) {
            list.add(rs.getString("name"));
        }
        return list;
    }
    void setCombBox(){
       province.addItemListener(new ItemListener() {
           @Override
           public void itemStateChanged(ItemEvent e) {
               try {
                  city.removeAllItems();
                   JComboBox com =(JComboBox)e.getSource();
                   for (String temp : inquiry2(com.getSelectedItem().toString())) {
                       city.addItem(temp);
                   }
               } catch (SQLException ex) {
                   throw new RuntimeException(ex);
               }
           }
           });
       city.addItemListener(new ItemListener() {
           @Override
           public void itemStateChanged(ItemEvent e) {
               try {
                   county.removeAllItems();
                   for (String temp:inquiry3(city.getSelectedItem().toString()))
                       county.addItem(temp);
               } catch (SQLException ex) {
                   throw new RuntimeException(ex);
               }
           }
       });
    }
   public inquiryAddress(JFrame jFrame,String title,boolean isMoel) throws SQLException {
       super(jFrame,title,isMoel);
       for (String temp:inquiry("province")) {
          province.addItem(temp);
       }
      setCombBox();
       //设置下拉框大小
       province.setSize(d);city.setSize(d);county.setSize(d);
       //组装视图
       box1.add(province);box1.add(city);box1.add(county);
       ok.setPreferredSize(dd);
       box2.add(ok);
       box.add(box1);box.add(box2);
       add(box);
       //设置窗口大小
      this.setSize(500,500);
       this.setName("农村人口统计系统");
       this.setVisible(true);
   }
}