？？为什么不能实现？？

有JcomboBox（学号）控件连接数据库，单击它，显示相应的记录，“姓名”“年龄”,为什么不能实现？？谢谢！！！

import java.sql.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class choice extends JFrame implements ActionListener,ItemListener
{
private Connection conn;
private Statement stmt;
private ResultSet rs;
private String url="jdbc:odbc:star";
JComboBox j;
JTextField t1,t2;
Container content;
public choice()
{
content=getContentPane();
content.setLayout(new FlowLayout());
j=new JComboBox();
t1=new JTextField(10);
t2=new JTextField(10);
content.add(j);
content.add(t1);
content.add(t2);
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
conn=DriverManager.getConnection(url);
stmt=conn.createStatementResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
String query;
query="select * from card";
rs=stmt.executeQuery(query);
rs.beforeFirst();
while(rs.next()) //显示JComboBox的内容(卡号)
{
String CardId=rs.getString(1);
j.addItem(CardId);


}
rs.close(); //关闭
stmt.close();

}catch(Exception ex)
{
System.out.println(ex.getMessage());
}


}

public static void main(String args[])
{
JFrame.setDefaultLookAndFeelDecorated(true);
choice cc=new choice();
cc.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
cc.setTitle("choice");
cc.setSize(500,500);
cc.show();

}

public void actionPerformed(ActionEvent ae)
{
}

public void itemStateChanged(ItemEvent ie)
{
try{
conn=DriverManager.getConnection(url);
stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);

String query1,strstr;
strstr=(String)(j.getSelectedItem());
query1="select * from card where 卡号='"+strstr+"'";


rs=stmt.executeQuery(query1);

t1.setText(rs.getString(2));
t2.setText(rs.getString(8));

rs.close(); //关闭
stmt.close();

}catch(Exception ex)
{
System.out.println(ex.getMessage());
}

}

}