public synchronized void addContactListListener(ContactListListener listener){
  if ((listener != null) && !mContactListListeners.contains(listener)) {
    mContactListListeners.add(listener);
  }
}

public synchronized void addContactListListener ( ContactListListener listener ) { if ( ( listener != null ) && ! mContactListListeners . contains ( listener ) ) { mContactListListeners . add ( listener ) ; } }
adds a listener to the manager so that it will be notified for contact list changed .
