How to set a limit on the size of a JDesktopPane?

Question

I have a JDesktopPane inside a JFrame, with a JInternalFrame inside the JDesktopPane. I want to give a maximum size to the JDesktopPane so that when i drag/move the internalframe, it doesnt go off the JDesktopPane screen.
I know many people uses ScrollBars to solve this but i dont want to use them & set a limit with boundaries of the JdesktopPane.
When users drag/move the internalframe towards the edge of the JDesktopPane, i want it to stick to the edge, like the effect of moving somthing over and you hit a wall.
Better example: Move a tetris block to the left wall and you hit the wall so it sticks to the wall and wouldn't allow you to move further left..
Tried "setMaximumSize(..)" but that didnt work.
After some googling and research, reading of web material i came up with following code:
Gives a new DesktopManager to the JDesktopPane & override the DragFrame method... but found that this method is not even getting called :S
//all gui setup code here
desktopPane.setDesktopManager(new DefaultDesktopManager() {
               private static final long serialVersionUID = 1L;
               public void dragFrame(JComponent f, int x, int y) {
                 if (f instanceof JInternalFrame || f instanceof JInternalFrame.JDesktopIcon) {
                   Dimension d = frame.getSize();  //desktopPane.getSize();
                     System.out.println(d.getWidth() + " " +  d.getHeight()); //just to see if it reaches here..
                      if (x < 0) {
                               x = 0;
                   else {
                     if (x + f.getWidth( ) > d.width) {
                                       x = d.width - f.getWidth( );
                   if (y < 0) {
                                 y=0;
                   else {
                     if (y + f.getHeight( ) > d.height) {
                                   y = d.height - f.getHeight( );
                 super.dragFrame(f, x, y);
             });I though that this method gets called automatically once you drag the internalframe.

Answer 1

[http://forums.sun.com/thread.jspa?threadID=5246887]
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