unable to get database table values into jtable on displayPane3

import java.awt.*;
import java.awt.GridLayout.*;
import java.awt.BorderLayout.*;
import javax.swing.*;
import javax.swing.JPanel.*;
import java.awt.event.*;
import java.sql.*;
import javax.swing.table.*;
import java.util.*;


//the Student main screen
public class Screen1 
{

private JPanel listItemsPane1, buttonsPane2,displayPane3; 
private JLabel l[];
private JButton jbutton1,jbutton2,jbutton3,jbutton4;
private JComboBox course, year, section;
private final String c[]= { "MCA", "MBA" };
private final String y[]= { "1st", "2nd", "3rd" }; 
private final String s[]= { "A", "B", "C", "D" };
private TextField tf;
private JTable table;
private Vector columnNames = new Vector();
private Vector data = new Vector();


//private Container c=getContentPane();

//other class
private table tab;
private int i;
Connection con;
PreparedStatement st;
ResultSet rs;

//initialize components
public Screen1()
{
JFrame sf1= new JFrame();

// set up panel
listItemsPane1= new JPanel();
buttonsPane2= new JPanel();
displayPane3= new JPanel();
listItemsPane1.setBorder(BorderFactory.createTitledBorder("Top"));
buttonsPane2.setBorder(BorderFactory.createTitledBorder("Bottom"));
displayPane3.setBorder(BorderFactory.createTitledBorder("Display"));




l= new JLabel[4];
l[0]= new JLabel("Course:");
l[1]= new JLabel("Year:");
l[2]= new JLabel("Section:");
l[3]= new JLabel("HT.No");

jbutton1= new JButton("OK");
jbutton2= new JButton("New");
jbutton3= new JButton("Edit");
jbutton4= new JButton("Delete");

tf= new TextField(12);

course= new JComboBox(c);
course.setMaximumRowCount(2);
year= new JComboBox(y);
year.setMaximumRowCount(3);
section= new JComboBox(s);
section.setMaximumRowCount(4);

//table=new JTable();
table=new JTable(data, columnNames);
JScrollPane scroll=new JScrollPane(table);
displayPane3.add(scroll);





//add listeners to components
/*
jbutton1.addActionListener(
new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
String ht=tf.getText();
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); 
con=DriverManager.getConnection("jdbc:odbc:oradsn","system","kumar");
System.out.println("connection success");
System.out.println(ht);

String query="SELECT * from std_details where HTNO=?";
PreparedStatement st=con.prepareStatement(que);
st.setString(1,ht);
rs=st.executeQuery();
while(rs.next()){
String htno=rs.getString("htno");
String name=rs.getString("sname");
String m=rs.getString("mob");
String mail=rs.getString("email");
String cou=rs.getString("course");
String yr=rs.getString("year");
String sec=rs.getString("section");
String sex=rs.getString("gender");

JOptionPane.showMessageDialog (null, "Htno:-"+ht+"\nName:-"+name+"\nCourse:-"+cou+"\nSec:-"+sec+"\nYear:-"+yr+
"\nMobile:-"+m+"\nMail:-"+mail, 
"Student Info.", JOptionPane.INFORMATION_MESSAGE);
System.out.println(name);
}
//System.out.println(htno);
st.close();
con.close();
}
catch(Exception e)
{
JOptionPane.showMessageDialog(null,"Retrieval failed");
}
}
}
); 
*/


jbutton1.addActionListener(
new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
Vector columnNames = new Vector();
Vector data = new Vector();
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); 
con=DriverManager.getConnection("jdbc:odbc:oradsn","system","kumar");
String sql = "Select * from std_details where htno=?";
PreparedStatement st = con.prepareStatement(sql);
//ResultSet rs = st.executeQuery();
String ht=tf.getText();
st.executeUpdate();
System.out.println("hw ru");

ResultSetMetaData metaData = rs.getMetaData();

int columns = metaData.getColumnCount();
for (int i = 1; i <= columns; i++) {
columnNames.addElement(metaData.getColumnName(i));
}

while (rs.next()) {
Vector row = new Vector(columns);
for (int i = 1; i <= columns; i++) {
row.addElement(rs.getObject(i));
}
data.addElement(row);
}
rs.close();
st.close();
}//try closed
 
catch (Exception e) {System.out.println(e);}
new JTable(data, columnNames);
TableColumn column;
for (int i = 0; i < table.getColumnCount(); i++) {
column = table.getColumnModel().getColumn(i);
//column.setMaxWidth(100);
}



}
}
); 




jbutton2.addActionListener(
new ActionListener() // listener for new event
{
public void actionPerformed(ActionEvent ae)
{
new New(); // calling the new class
}
}
);

jbutton3.addActionListener(
new ActionListener() // listener for edit event
{
public void actionPerformed(ActionEvent ae)
{
new Edit();// calling the edit class
//new New();
}
}
);

jbutton4.addActionListener(
new ActionListener() // listener for delete event
{
public void actionPerformed(ActionEvent ae)
{
}
}
);

course.addItemListener(
new ItemListener()// course item listener
{
public void itemStateChanged(ItemEvent ie)
{
}
}
);

//set layout and add compnents to panel 1

listItemsPane1.setLayout(new FlowLayout());
listItemsPane1.add(l[0]);
listItemsPane1.add(course);
listItemsPane1.add(l[1]);
listItemsPane1.add(year);
listItemsPane1.add(l[2]);
listItemsPane1.add(section);
listItemsPane1.add(l[3]);
listItemsPane1.add(tf);
listItemsPane1.add(jbutton1);

//set layout and add compnents to panel 2
buttonsPane2.setLayout(new FlowLayout());
buttonsPane2.add(jbutton2);
buttonsPane2.add(jbutton3);
buttonsPane2.add(jbutton4);







sf1.getContentPane();
sf1.setLayout(new GridLayout(3,1));
sf1.add(listItemsPane1);
sf1.add(displayPane3);
sf1.add(buttonsPane2);
sf1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//getContentPane.add(sf1);
sf1.setSize(600,300);
sf1.setVisible(true);

}

public static void main(String[] ar)
{
Screen1 scr= new Screen1();
}
}