Problème avec les fenêtres modales

import java.awt.Dialog.ModalityType;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JDialog;

public class Test {

    public static void main(String[] args) {

        int N = 5;

        JDialog[] dialogs = new JDialog[N];

        dialogs[0] = new JDialog();
        for (int i = 1; i < N; i++)
            dialogs[i] = new JDialog(dialogs[i - 1], "", ModalityType.DOCUMENT_MODAL);

        for (int i = 0; i < N; i++) {
            JButton button = new JButton(String.valueOf(i));
            if (i != N - 1) {
                JDialog next = dialogs[i + 1];
                button.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        next.setVisible(true);
                    }
                });
            }
            dialogs[i].add(button);
        }

        for (int i = 0; i < N; i++) {
            dialogs[i].pack();
            dialogs[i].setLocationByPlatform(true);
        }

        dialogs[0].setVisible(true);
    }
}