Mine

public class pnb2 extends JFrame {
    private JPanel painel;
    private JLabel label;
    private JButton bot;
    
    pnb2() {
        this.setLayout(new GridLayout(1,1));
        painel = new JPanel();
        label = new JLabel("label");
        bot = new JButton("button");
        bot.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                pressedButton(evt);
            }
        });
        painel.setLayout(new GridLayout(2,1));
        painel.setAlignmentY(painel.CENTER_ALIGNMENT);
        this.add(painel);
        painel.add(label);
        painel.add(bot);
        this.pack();
    }
    
    public void pressedButton(ActionEvent e) {
        pnb lala = new pnb();
        this.remove(painel);
        painel = lala.getPainel();
        this.add(painel);
    }
    
    public static void main(String[] args) {
        new pnb2().setVisible(true);
    }
}