Go4Expert - code compilation problem,please help

Code:
import java.awt.*;

import java.sql.*;

import java.awt.event.*;

public class pubinfo implements ActionListener

{

Label lpubid;

TextField pub_id;

Button insert;

Panel p1;

Frame f1;

 Connection con;

PreparedStatement stat;

Statement stmt;

ResultSet rs;

public pubinfo()

{

try 

{

        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();

String url = "jdbc:odbc:+Library";

Connection db_connection = DriverManager.getConnection (url, "sa", "friendship");

Statement stmt = db_connection.createStatement();

}

catch (ClassNotFoundException cnfe) 

{

        System.err.println ("Unable to load database driver");

        System.err.println ("Details : " + cnfe);

        System.exit(0);

}

}

public void display()

{

f1 =new Frame("pubinfo");

p1 =new  Panel();

lpubid =new Label("Login");

pub_id=new TextField(6);

insert =new Button("ok");



lpubid.setBounds(250,35,200,40);

pub_id.setBounds(100,90,100,25);

p1.add(lpubid);

p1.add(pub_id);



insert.addActionListener(this);

}





public void actionPerformed(ActionEvent ae)

{

if(ae.getActionCommand() == "ok")

{

try

{

stat=con.prepareStatement("INSERT INTO pubinfo VALUES(?)");

String pid=pub_id.getText();

stat.setString(1,pid);

stat.executeUpdate();

pub_id.setText(" ");

}



catch(Exception e)

{

System.out.println(" Error1:" +e);

error.SetText("row not inserted");

}

}

}



public static void main(String args[])

{

pubinfo p= new pubinfo();

p.display();



}

}