Programmer - [Java] Recursion causes exit to exit all JFrames (terminates app)

Programmer Question

I have made an application that gives the user the option to open up a new spawn of the application entirely. When the user does so and closes the application the entire application terminates; not just the window.

How should I go about recursively spawning an application and then when the user exits the JFrame spawn; killing just that JFrame and not the entire instance?

Here is the relevant code:

            [...]
            JMenuItem newMenuItem = new JMenuItem ("New");
            newMenuItem.addActionListener(new ActionListener()
            {
                public void actionPerformed(ActionEvent e)
                {

                    new MainWindow();
                }
            });
            fileMenu.add(newMenuItem);

            [....]

            JMenuItem exit = new JMenuItem("Exit");
            exit.addActionListener(new ActionListener()
            {
                public void actionPerformed(ActionEvent e)
                {
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                }
            });
            fileMenu.add(exit);
            [...]

Find the answer here