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

public class MyFirstBigApp extends JFrame {
    private JPanel panel;
    private JButton button1, button2, button3;

    public MyFirstBigApp(String title) throws HeadlessException {
        super(title);
        setVisible(true);
        Dimension size = Toolkit.getDefaultToolkit().getScreenSize();
        setSize(size.width,size.height);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        panel = new JPanel();
        panel.setLayout(new GridBagLayout());

        button1 = new JButton("Ahoj");
        button1.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(MyFirstBigApp.this, "Ahoj");
            }
        });
        button2 = new JButton("Čau");
        button3 = new JButton ("Nazdar");

        GridBagConstraints g = new GridBagConstraints();
        g.gridy = 0;
        g.gridx = 0;
        g.ipadx = 20;
        g.ipady = 20;
        g.gridwidth = 2;
        g.fill = MAXIMIZED_HORIZ;

        panel.add(button1, g);

        g.gridy = 1;
        g.gridwidth = 1;

        panel.add(button2, g);

        g.gridx = 1;

        panel.add(button3, g);

        add(panel);




    }

    public static void main(String[] args) {
        new MyFirstBigApp("My app");
    }
}