import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class oppgave1 {
    public static void main(String[] args){
        try {
            UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
        } catch (Exception e) { System.exit(1); }

        JFrame vindu = new JFrame();
        JPanel panel = new JPanel();
        vindu.add(panel);

        vindu.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        panel.setLayout(new GridLayout(2,3));

        for (int i  = 0; i<6; i++){
            panel.add(new GridKnapp(""+i));
        }
        vindu.setSize(500, 500);
        vindu.setLocationRelativeTo(null);
        vindu.setVisible(true);


    }
    
    private static class GridKnapp extends JButton {
        private String tall;
   
        public GridKnapp(String tall){
            super(tall);
            this.tall = tall;
            addActionListener(new EndreKnappTekst());
        }
   
        class EndreKnappTekst implements ActionListener {
            @Override
            public void actionPerformed(ActionEvent e) {
                if(getText().equals(tall)){
                    setText(":)");
                } else {
                    setText(tall);
                }
        }
    }
    }
}