Java Swing Switch Between JInternalFrame and JFrame extends

Question

I am building an application that uses a JDesktopPane and JInternalFrames which at the moment works like this

desktopPane.java

// this program handles the main desktop pane

public class desktopPane extends JFrame {

    static JDesktopPane mainDesktopPane;
    static JMenuItem itemChildProgram;

    public desktopPane() {
        mainSetup();
        mainBuild();
        mainActions();
    }

    public static void main(String[] args) {
        desktopPane mainFrame = new desktopPane();
        mainFrame.setVisible(true);
    }

    public void mainSetup() {
        // set title and size and close operation etc.
    }

    public void mainBuild() {
        mainDesktopPane      = new JDesktopPane();

        JMenuBar mainMenuBar = new JMenuBar();
        JMenu menuRun        = new JMenu("Run");
        itemChildProgram     = new JMenuItem("Child Program");

        add(mainDesktopPane);

        setJMenuBar(mainMenuBar);
        mainMenuBar.add(menuRun);
        menuRun.add(itemChildProgram);
    }

    public void mainActions() {
        actionChildProgram execChildProgram = new actionChildProgram();
        itemChildProgram.addActionListener(execChildProgram);
    }

    public class actionChildProgram implements ActionListener {
        public void actionPerformed(ActionEvent execChildProgram) {
            childProgram classChildProgram = new childProgram(mainDesktopPane);
        }
    }

}

So that program just builds my main screen and it has a button which calls my other program

childProgram.java

public class childProgram {

    public childProgram(JDesktopPane mainDesktopPane) {
        // database connection and data retrieval goes here

        childProgramGUI child = new childProgramGUI();
        child.setVisible(true);
        mainDesktopPane.add(child);
    }

}

So this program just prepares some data and a bunch of other stuff and then calls the gui where the data is visible. The gui file for now is terribly simple

childProgramGUI.java

public class childProgramGUI extends JInternalFrame {
    // some gui design goes here
}

This works fine when calling childProgram.java from the JDesktopPane in desktopPane.java but how can I call childProgram.java as a standalone program without adding it to the mainDesktopPane as a child.

I only need the childProgram to run outside of the desktopPane when a condition is met.

If I make the following alterations to the code

• change childProgramGUI.java to JFrame instead of JInternalFrame
• remove the line in childProgram.java: mainDesktopPane.add(child);

Then it works as I intend but I can't change the extends of the childProgramGUI.java to JFrame with just code (that I know of)

UPDATE

So far the only solution I have for this is to just duplicate my gui programs so now I have

childProgramGUI.java

public class childProgramGUI extends JInternalFrame {
    // some gui design goes here
}

As well as the standalone one with all the exact same code except it's a JFrame

childProgramGUI_Standalone.java

public class childProgramGUI_Standalone extends JFrame {
    // the exact same gui design goes here
}

And then put a condition on my mainDesktopPane.add(child). I'm not happy with it but it works to run the program in and out of it's JDesktopPane