TestAppletDialog.java
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;

public class TestAppletDialog extends Applet 
                                                implements ActionListener{
        private Button bAbout;
        private SemiAboutDialog sad;
        
        public void init(){
                bAbout = new Button("about");
                add(bAbout);
                bAbout.addActionListener(this);
        }
        public void actionPerformed(ActionEvent e)
        {
                if(e.getSource() == bAbout){
                // test op nullwaarde van sad, om te 
                // zorgen dat alleen een dialoog geopend
                // wordt, als er nog geen open is
                        if (sad == null)
                                sad = new SemiAboutDialog(this);
                }
        }
        public void nullWindow(){
                // de dialoog wordt gesloten:
                // maak sad null, zodat er weer een
                // nieuwe dialoog geopend kan worden
                sad = null;
        }
}

class SemiAboutDialog extends Frame{
        final TestAppletDialog tad;
            
            SemiAboutDialog(TestAppletDialog TAD){
                    
                    super("Applet About Demo");
                    tad = TAD;
                    setLayout(new FlowLayout());
                    add(new Label("Hier had info over het"));
                    add(new Label("programma kunnen staan!"));
                    addWindowListener(new WindowAdapter() {
                            public void windowClosing(
                                                                          WindowEvent e) {
                                    dispose();
                                    tad.nullWindow();
                            }
                    });
                    setSize(180, 110);
                    setLocation(50, 100);          
                    show();
            }      
}