Отобразить кнопку поверх JScrollPane Java Swing

import javax.swing.*;
import javax.swing.border.LineBorder;
import javax.swing.table.DefaultTableModel;
import java.awt.*;
 
class Item {
    public Item(int id, String nick, String content) {
        this.id = id;
        this.nick = nick;
        this.content = content;
    }
 
    @Override
    public String toString() {
        return nick + ": "
                + content;
    }
 
    int id;
    String nick;
    String content;
}
 
class OverlayLayoutExample {
    public static void main(String[] args) {
        JPanel panel = createPanel();
        JFrame frame = createFrame();
        frame.add(panel);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
 
    private static JPanel createPanel() {
        JPanel mainPanel = new JPanel(){
            @Override
            public boolean isOptimizedDrawingEnabled() {
                return false;
            }
        };
        mainPanel.setLayout(new OverlayLayout(mainPanel));
 
        JButton button = new JButton("Show Message");
        button.setAlignmentX(0.5f);
        button.setAlignmentY(0.5f);
 
 
        JTable table = new JTable();
//        mainPanel.add(table);
 
        JScrollPane scroll = new JScrollPane(table);
        mainPanel.add(scroll);
 
        DefaultTableModel tableModel = new DefaultTableModel();
        table.setModel(tableModel);
 
        tableModel.addColumn("Column 1");
        table.setTableHeader(null);
        table.setShowGrid(false);
        table.setRowHeight(25);
        tableModel.insertRow(0, new Object[] { new Item (1, "456", "New text") });
 
        Item item = new Item(1, "123", "Very very very very very very very very very very very very long text message");
 
        for(int i = 0; i < 500; i++)
            tableModel.insertRow(tableModel.getRowCount(), new Object[] { item });
 
        JPanel popupPanel = createPopupPanel(button);
        popupPanel.setAlignmentX(0.1f);
        popupPanel.setAlignmentY(0.1f);
 
        button.addActionListener(e -> {
            button.setEnabled(false);
            popupPanel.setVisible(true);
        });
 
        mainPanel.add(popupPanel);
//        mainPanel.add(button);
 
        return mainPanel;
    }
 
    private static JPanel createPopupPanel(JComponent overlapComponent) {
        JPanel popupPanel = new JPanel(new BorderLayout());
        popupPanel.setOpaque(false);
        popupPanel.setMaximumSize(new Dimension(150, 70));
        popupPanel.setBorder(new LineBorder(Color.gray));
        popupPanel.setVisible(true);
 
        JLabel label = new JLabel("HI there!");
        popupPanel.add(wrapInPanel(label), BorderLayout.CENTER);
 
        JButton popupCloseButton = new JButton("Close");
        popupPanel.add(wrapInPanel(popupCloseButton), BorderLayout.SOUTH);
 
        popupCloseButton.addActionListener(e -> {
            overlapComponent.setEnabled(true);
            popupPanel.setVisible(false);
        });
 
        return popupPanel;
    }
 
    private static JPanel wrapInPanel(JComponent component) {
        JPanel jPanel = new JPanel();
        jPanel.setBackground(new Color(50, 210, 250, 150));
        jPanel.add(component);
        return jPanel;
    }
 
 
    private static JFrame createFrame() {
        JFrame frame = new JFrame("OverlayLayout Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(new Dimension(400, 300));
        return frame;
    }
}