Creates a new JFC (Swing) internal frame that can be placed onto a JDesktopPane to provide an MDI user interface. Typically you would create an internal frame class containing display elements for each individual frame. Treat each internal frame class like a JFrame class. Then create a JFrame (or JApplet) application with a JDesktopPane on it. Add the internal frames to the desktop pane using code, or using the Copy and Paste functions in the Projects window after the internal frames are compiled.