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

public class Teller {

    static int teller = 0;

    public static void main(String[] args) {

        try {
            UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
        } catch (Exception e) {
            System.exit(1);
        }

        JFrame vindu = new JFrame("Teller");
        vindu.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        vindu.setPreferredSize(new Dimension(500, 300));

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

        JLabel tellerTekst = new JLabel("Tall: " + teller);
        JButton knapp = new JButton("?k teller");

        knapp.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                teller++;
                tellerTekst.setText("Tall: " + teller);
            }
        });

        panel.add(tellerTekst);
        panel.add(knapp);

        vindu.pack();
        vindu.setLocationRelativeTo(null);
        vindu.setVisible(true);
    }
}