import javax.swing.*; 
import java.awt.*; 
import java.awt.event.*;

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

        JFrame vindu = new JFrame("Hilsevindu");
        vindu.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();
        JLabel tekstfelt = new JLabel("");

        JButton knapp = new JButton("Hilseknapp");

        
        panel.add(tekstfelt);
        panel.add(knapp);
        vindu.add(panel);

        knapp.addActionListener(new ActionListener(){
            private boolean hilst = false; 

            @Override 
            public void actionPerformed (ActionEvent e){
                
                if (!hilst) {
                    tekstfelt.setText("Hei p? deg");
                    hilst = true; 
                }
                else { 
                    tekstfelt.setText("Ha det bra!");
                    hilst = false;
                }
            }
        });
        
        vindu.pack(); 
        vindu.setLocationRelativeTo(null);
        vindu.setVisible(true);
    }
}