Problem extending an inner class

[Daniele Lugli]

Could somebody try the following application? It raises a null pointer
exception when class Dialog2, extending class Dialog1, tries to access a
data member of the outer class.
Please consider that I am really a java newbie (about 10 days of
programming) so I'm not saying I've found a bug, the problem is probably
mine.

Thank you,
Daniele Lugli


// File name: Wrong.java

import java.awt.*;
import java.awt.event.*;
import java.lang.String;
import java.text.*;
import java.util.*;

public class Wrong extends Frame {

  public static void main (String args[]) throws Exception {
    new Wrong ();
  }

  public Wrong () throws Exception {
    super ();
    setBounds (300, 100, 300, 100);
    setVisible (true);

    i = 5;

    new Dialog2 (this);
  }

  private void quit () {
    setVisible (false);
    dispose ();
    System.exit (0);
  }


  class Dialog1 extends Dialog implements ActionListener {
    Dialog1 (Frame parent) {
      super (parent, "Dialog", true );
      setBounds (400, 200, 100, 75);
      okButton = new Button ("OK");
      okButton.addActionListener (this);
      add (okButton);
      setVisible (true);
    }
    public void actionPerformed (ActionEvent aevt) {
      
      System.out.println ("Dialog1: i=" + i);

    }
    private Button okButton;
  }

  class Dialog2 extends Dialog1 {
    Dialog2 (Frame parent) {
      super (parent);
    }
    public void actionPerformed (ActionEvent aevt) {
      super.actionPerformed (aevt);
      
      System.out.println ("Dialog2: i=" + i);

      quit ();
    }
  }

  int i;

}