public void addGraphicsCard() {
   helper.decorate((Composite) _computer, Decoratable.GRAPHICSCARD);
 }
 public void addHardDrive() {
   helper.decorate((Composite) _computer, Decoratable.HARDDRIVE);
 }
 public void addRam() {
   helper.decorate((Composite) _computer, Decoratable.RAM);
 }