Listing 1.
         public class IllusionApplet extends Applet{
             private int canvasWidth, canvasHeight;
             private RegisterObject ro;
             /* Shapes (models or observables) used
              in this applet */
             private StandardLineShape stdLine;

             public void init(){
             // this object helps coordinates &
                 between shapes
             ro = new RegisterObject
              (lineThicknessInPixels);

             /* create models or observables */
             stdLine = new
StandardLineShape(canvasWidth, canvasHeight, ro);
             }
 

Listing 2.
        // methods / public / IObservable implementation
        public void addIObserver(IObserver anIObserver) {
        myObservableComponent.addIObserver(anIObserver);
        }

        public void deleteIObserver(IObserver anIObserver) {
        myObservableComponent.deleteIObserver(anIObserver);
        }

        public void deleteIObservers() {
        myObservableComponent.deleteIObservers();
        }

Listing 3.
        // IObservable implementation
        public void addIObserver(IObserver anIObserver) {
            myObservableComponent.addIObserver &
          (anIObserver); }

        public void deleteIObserver(IObserver anIObserver) {
            myObservableComponent.deleteIObserver &
          (anIObserver); }

        public void deleteIObservers() {
            myObservableComponent.deleteIObservers(); }

        // IObserver implementation
        public void update(Object theObserved,  &
          Object changeCode){
           updateMe();
           myObservableComponent.notifyIObservers &
            (theObserved,changeCode);
        }
 
 

©Board of Trustees, University of Illinois, 1997. Information concerning  use of these classes and interfaces  can be obtained from the Department  of Psychology, University of Illinois, 603 E. Daniel, Champaign, Illinois 61801. Redistribution and  use, with and without modifications, are permitted for any purpose provided that  the source code retain the above copyright notice.  All publications  or advertising materials mentioning features or use of this software must acknowledge that it was developed by the University of Illinois at Urbana-Champaign and credit the contributors. THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND THE CONTRIBUTORS “AS IS” WITH NO WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED. In no event shall the University or the contributors be liable for any damages suffered by the users arising out of the  use of this software, even if advised of the possibility of such damage.