Как проще вызвать новое окно внутри окна?

settingsButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                ConfigDialog dialog = new ConfigDialog(frame, config);

                dialog.create();
            }
        });

public void create(){
        GridLayout layout = new GridLayout(4, 2, 8, 8);

        BorderLayout borderLayout = new BorderLayout(GAP, GAP);

        JPanel panel = new JPanel(layout);
        panel.setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
        panel.setLayout(borderLayout);

        panel.add(createLabels(), BorderLayout.WEST);
        panel.add(createTextFields(), BorderLayout.CENTER);
        panel.add(createButtons(), BorderLayout.SOUTH);

        getContentPane().add(panel);
        pack();
        setLocationRelativeTo(getOwner());
        setVisible(true);
    }