public void removeObserver(IBicycleObserver obj)
 {
     observerList.Remove(obj);
 }
 public void removeObserver(IBicycleObserver obj)
 {
     observerList.Remove(obj);
 }
 public void addObserver(IBicycleObserver obj)
 {
     observerList.Add(obj);
 }
 public void addObserver(IBicycleObserver obj)
 {
     observerList.Add(obj);
 }