How to insert values in java

import java.sql.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class inst extends Frame implements ActionListener
{
Connection con=null;
PreparedStatement st;
Frame f;
Button b;
Label l1,l2,l3;
TextField t1,t2,t3;
FlowLayout fl;
inst()
{
f=new Frame("insert");
l1=new Label("Enter name");
l2=new Label("Enter roll no");
l3=new Label("Enter marks");
t1=new TextField(10);
t2=new TextField(10);
t3=new TextField(10);
fl=new FlowLayout();
f.setLayout(fl);
f.add(l1);
f.add(t1);
f.add(l2);
f.add(t2);
f.add(l3);
f.add(t3);
b=new Button("Insert");
f.add(b);
b.addActionListener(this);
f.setSize(200,200);
f.setVisible(true);
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:harsh");
st=con.prepareStatement("INSERT INTO stu VALUES(?,?,?)");
}
catch(Exception e)
{
}
}
public void actionPerformed(ActionEvent ee)
{
if(ee.getSource()==b)
{
try
{
st.setString(1,t1.getText());
st.setString(2,t2.getText());
st.setString(3,t3.getText());
st.executeUpdate();
JOptionPane.showMessageDialog(this,"Record inserted");
}
catch(Exception e)
{
}
}
}
public static void main(String arg[])
{
inst obj=new inst();
}
}