private void setCurrentElement(PhysicsElement e) {
      if (currentElement != null) {
         currentElement.setReleased();
         currentElement = null;
      }
      if (e != null) { 
         currentElement = e;
         currentElement.setSelected();
         
         if (currentElement instanceof Ball) {
            System.out.println("BallSelected");
         }    
         else if (currentElement instanceof FixedHook){
           System.out.println("FixedHook Selected");
         }
         else if (currentElement instanceof Spring){     
            System.out.println("Spring Selected");
         }
      }
   }