Insert, update, delete, and select with Servlet and Access

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

public class index extends HttpServlet
{
Connection con;
PreparedStatement ps;
ResultSet rs;
public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException
{
response.setContentType("text/html");
PrintWriter out=response.getWriter();

String roll=request.getParameter("roll");
String name=request.getParameter("name");
String city=request.getParameter("city");

out.println("<form name=f1>");
out.println("Roll:<input name='roll'><br>");
out.println("Name:<input name='name'><br>");
out.println("City:<input name='city'><br>");
out.println("<input type=submit name='Insert' value='Insert'>");
out.println("<input type=submit name='Update' value='Update'>");
out.println("<input type=submit name='Delete' value='Delete'>");
out.println("</form>");

out.println("<table><tr><th>Roll<th>Name<th>City</tr>");
try{
connect();
ps=con.prepareStatement("select * from stud");
rs=ps.executeQuery();
while(rs.next())
{
out.println("<tr><td>"+rs.getString(1)+"");
            out.println("<td>"+rs.getString(2)+"");
out.println("<td>"+rs.getString(3)+"</tr>");
}
con.close();
}
catch(Exception e)
{
System.out.println(e);
}
out.println("</table>");

if(request.getParameter("Insert")!=null)
putData("insert into Stud values('"+roll+"','"+name+"','"+city+"')");
if(request.getParameter("Update")!=null)
putData("update Stud set name='"+name+"',city='"+city+"' where roll='"+roll+"'");
if(request.getParameter("Delete")!=null)
putData("delete from Stud where roll='"+roll+"'");
}

public void connect()
{
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:MyDb");
}
catch(Exception e){
System.out.println(e);
}
}

//single method to insert, update, delete
public void putData(String query)
{
try{
connect();
ps=con.prepareStatement(query);
ps.executeUpdate();
con.close();
}
catch(Exception e)
{
System.out.println(e);
}
}
}