code: private void onBusStopChanged(BusStop stop) {
  		if (stop.getContainer() == this) {
  			final boolean oldValidity = !ListUtil.contains(this.invalidBusStops, INVALID_STOP_COMPARATOR, stop);
  			final boolean currentValidity = stop.isValidPrimitive();
  			if (oldValidity != currentValidity) {
  				if (currentValidity) {
  					ListUtil.remove(this.invalidBusStops, INVALID_STOP_COMPARATOR, stop);
  					this.validBusStops.add(stop);
  				} else {
  					this.validBusStops.remove(stop);
  					ListUtil.addIfAbsent(this.invalidBusStops, INVALID_STOP_COMPARATOR, stop);
  				}
  			}
  		}
  	}
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