Modeless dialog test

package modeless;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class ModelessTest extends JFrame {

    private static int dialogCount = 0;

    private JTextArea taMessages = new JTextArea(10, 0);

    public ModelessTest() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setTitle("Modeless dialogs with callbacks");

        setLayout(new BorderLayout());

        taMessages.setEditable(false);
        add(taMessages, BorderLayout.CENTER);

        JButton btnSpawnModeless = new JButton("Spawn modeless dialog");
        btnSpawnModeless.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                ++dialogCount;
                final String dialogTitle = "Dialog #" + dialogCount;
                DialogCallback callback = new DialogCallback() {

                    @Override
                    public void ok() {
                        taMessages.append("OK: " + dialogTitle + "\n");
                    }

                    @Override
                    public void cancel() {
                        taMessages.append("Cancel: " + dialogTitle + "\n");
                    }
                };
                MyModelessDialog dialog = new MyModelessDialog(ModelessTest.this, dialogTitle, callback);
                dialog.setVisible(true);
            }
        });
        add(btnSpawnModeless, BorderLayout.SOUTH);
        pack();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new ModelessTest().setVisible(true);
            }
        });
    }

}

class MyModelessDialog extends JDialog {
    private final DialogCallback cbk;
    private JButton okButton, cancelButton;

    public MyModelessDialog(Window owner, String title, DialogCallback callback) {
        super(owner, title);
        cbk = callback;
        setModalityType(ModalityType.MODELESS);

        createLayout();

        okButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                onOK();
            }
        });

        cancelButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                onCancel();
            }
        });

        // Treat closing the dialog the same as pressing "Cancel":
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                onCancel();
            }
        });
    }

    private void createLayout() {
        setLayout(new FlowLayout());

        okButton = new JButton("OK");
        add(okButton);

        cancelButton = new JButton("Cancel");
        add(cancelButton);

        pack();
    }

    private void onOK() {
        cbk.ok();
        setVisible(false);
    }

    private void onCancel() {
        cbk.cancel();
        setVisible(false);
    }
}


interface DialogCallback {
    void ok();

    void cancel();
}