GUI question: What must I call to open a new window within the same window? [on hold]

public class JDial extends JDialog {

private static final long serialVersionUID = -26565050431585019L;
private final JPanel contentPanel = new JPanel();

public static void main(String[] args) {
    try {
        JDial dialog = new JDial();
        dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
        dialog.setVisible(true);
        dialog.setTitle("Heavy Evil");



    } catch (Exception e) {
        e.printStackTrace();
    }
}

public JDial() {
    setBounds(0, 0, 1280, 800);
    getContentPane().setLayout(new BorderLayout());
    contentPanel.setLayout(new FlowLayout());
    contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
    getContentPane().add(contentPanel, BorderLayout.CENTER);


    JPanel buttonPane = new JPanel();
    buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
    getContentPane().add(buttonPane, BorderLayout.SOUTH);
    {
        JButton okButton = new JButton("Save");
        okButton.setActionCommand("Save");
        buttonPane.add(okButton);
        getRootPane().setDefaultButton(okButton);

    }
    {
        JButton cancelButton = new JButton("Exit");
        cancelButton.setActionCommand("Exit");
        buttonPane.add(cancelButton);
    }

    {
        JPanel textPane = new JPanel();
        textPane.setLayout(new FlowLayout(FlowLayout.LEFT));
        getContentPane().add(textPane, BorderLayout.NORTH);
        {
            JTextArea textArea = new JTextArea("Enter Message", 10, 20);
            textPane.add(textArea);
            textArea.setWrapStyleWord(true);
            textArea.setEditable(true);
            textArea.setFont(Font.getFont(Font.SANS_SERIF));
            textArea.setBounds(0, 0, 10, 20);
            textArea.setVisible(true);
            textArea.enableInputMethods(isEnabled());
            textArea.computeVisibleRect(getBounds());
        }

        {
            JButton newButton = new JButton("Send");
            newButton.setActionCommand("Send");
            textPane.add(newButton);
            newButton.setEnabled(true);

        }


    }

}

}