This interface is implemented by components that have a single JRootPane child: JDialog, JFrame, JWindow, JApplet, JInternalFrame. The methods in this interface are just covers for the JRootPane properties, e.g. getContentPane() is generally implemented like this:

     public Container getContentPane() {
         return getRootPane().getContentPane();
     }
 

This interface serves as a marker for Swing GUI builders that need to treat components like JFrame, that contain a single JRootPane, specially. For example in a GUI builder, dropping a component on a RootPaneContainer would be interpreted as frame.getContentPane().add(child).

For conveniance JFrame, JDialog, JWindow, JApplet and JInternalFrame, by default, forward, by default, all calls to the add, remove and setLayout methods, to the contentPane. This means you can call:

 rootPaneContainer.add(component);
 

instead of:

 rootPaneContainer.getContentPane().add(component);
 

The behavior of the add and setLayout methods for JFrame, JDialog, JWindow, JApplet and JInternalFrame is controlled by the rootPaneCheckingEnabled property. If this property is true (the default), then calls to these methods are forwarded to the contentPane; if false, these methods operate directly on the RootPaneContainer. This property is only intended for subclasses, and is therefore protected.

 
    getRootPane().setLayeredPane(layeredPane);