Overriding default mouse behavior

To override the default mouse behavior in a 2D VisAD window,
I was advised here to take a look at
        http://www.unidata.ucar.edu/glimpse/visad-lis/2255
I believe I have reproduced the logic of that example below,
and so I wonder why I got the following run-time error:

"Exception in thread "main" visad.VisADError: cannot construct
class MouseSupercede at visad.java2d.DefaultDisplayRendererJ2D.
createSceneGraph(DefaultDisplayRenderer"...[etc.]

---------------------- EXAMPLE: -----------------
import visad.*;
import visad.java2d.*;
import java.rmi.RemoteException;
import java.awt.*;
import javax.swing.*;

public class a11 {

public
a11 (String[] args) throws RemoteException, VisADException {

    DisplayRendererJ2D DR
         new DefaultDisplayRendererJ2D(MouseSuperceded.class);
    DisplayImpl theDisp = new DisplayImplJ2D("theDisp", DR);
}

public static void main(String[] args)
    throws RemoteException, VisADException {
        new a11(args);
        }
}


class DeadMouse extends MouseHelper {

public DeadMouse(DisplayRenderer DR, MouseBehavior MB) {
        super(DR, MB);
}
}

class MouseSuperceded extends MouseBehaviorJ2D {

public MouseSuperceded(DisplayRendererJ2D dRd {
        super(dRd, DeadMouse.class);
}
}
---------------- end of example -----------------------

As a sanity check, if I replace the line 
         new DefaultDisplayRendererJ2D(MouseSuperceded.class);
with
  new DefaultDisplayRendererJ2D
        (visad.java2d.MouseBehaviorJ2D.class)
I don't get the error.