code: public boolean setBusStop(BusStop busStop) {
  		final BusStop old = getBusStop();
  		if ((busStop == null && old != null)
  			|| (busStop != null && !busStop.equals(old))) {
  			if (old != null) {
  				old.removeBusHalt(this);
  			}
  			this.busStop = busStop == null ? null : new WeakReference<>(busStop);
  			if (busStop != null) {
  				busStop.addBusHalt(this);
  			}
  			clearPositionBuffers();
  			fireShapeChanged();
  			checkPrimitiveValidity();
  			return true;
  		}
  		return false;
  	}
docs: Set the bus stop associated to this halt.
  
  @param busStop is the bus stop associated to this halt,
  or <code>null</code> if this halt is not associated to
  a bus stop.
  @return <code>true</code> if the bus stop was correctly set,
  otherwise <code>false</code>.