cerco di essere più preciso, questo è il codice completo:
codice:
public class Main extends javax.swing.JFrame {
     public Main() {
            initComponents();
           //PANNELLO ESISTENTE
            gridPanel = new JPanel(new GridLayout(0, 1));
            JPanel borderLayoutPanel = new JPanel(new BorderLayout());
            borderLayoutPanel.add(gridPanel, BorderLayout.PAGE_START);
            JScrollPane scrollPane = new JScrollPane(borderLayoutPanel);
            scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
            add(scrollPane);

             Avvio();

    }
     private void Avvio() {
            JPanel pane = new JPanel(new GridBagLayout());
            pane.setBorder(BorderFactory.createLineBorder(Color.BLUE));


            for (int i = 0; i < 10; i++) {
                JButton button;
                pane.setLayout(new GridBagLayout());
                GridBagConstraints c = new GridBagConstraints();
                c.fill = GridBagConstraints.HORIZONTAL;
                c.anchor = GridBagConstraints.PAGE_START;


                button = new JButton("Button 1");
                c.weightx = 0.5;
                c.gridx = 0;
                c.gridy = 0;
                pane.add(button, c);


                button = new JButton("Button 2");
                c.gridx = 0;
                c.gridy = 1;
                pane.add(button, c);


                button = new JButton("Button 3");
                c.gridx = 1;
                c.gridy = 1;
                pane.add(button, c);
            }


        }