Problem with actionperformed callback

I tried to create function, what shows textdialog, when client press the buton, but the problem is that i have defined frame under public static void main and in ActionPerformed callback first parameter "frame" is undefined. How could i fix this?

import java.awt.*;



import java.awt.event.*;



import java.applet.Applet;



import javax.swing.*;

public class Vestlus extends Applet implements ActionListener {



TextField tf = new TextField("");



Button nupp = new Button(" Sisesta ");

public Vestlus()



{



add(tf);



add(nupp);



nupp.addActionListener(this);

}



public void actionPerformed(ActionEvent e)



{



if(e.getSource() == nupp)



{



JOptionPane.showMessageDialog(frame,"Hoiatus","Vää rtused ei klapi!", JOptionPane.INFORMATION_MESSAGE);

}



}



public static void main(String args[])



{

JFrame frame = new JFrame("Project LA");



frame.add(new Vestlus());



frame.setSize(300,200);



frame.setVisible(true);



frame.setDefaultCloseOperation(1);

}

}