Mutable Models Bug

PricedVehicles.java

/**
 * Provides a stream of vehicles that have a price.
 */
public class PricedVehicles {

    private Observable<List<Vehicle>> pricedVehicles;

    public PricedVehicles(VehicleStream vehicleStream, PricingStream pricingStream) {
        this.pricedVehicles = Observable.combineLatest(
                vehicleStream.vehicles(),
                pricingStream.prices(),
                PricedVehicles::filterVehiclesWithoutPrice);
    }

    /**
     * @return a stream that emits lists of priced vehicles.
     */
    public Observable<List<Vehicle>> stream() {
        return pricedVehicles;
    }

    /**
     * Removes vehicles that don't have a price in the prices map.
     * @param vehicles the list of vehicles that are available.
     * @param prices a map containing the prices of vehicles.
     */
    private static List<Vehicle> filterVehiclesWithoutPrice(
            List<Vehicle> vehicles,
            Map<VehicleId, Price> prices) {
        List<Vehicle> vehiclesToRemove = new ArrayList<>();
        for(Vehicle vehicle : vehicles) {
            if (prices.get(vehicle.id()) == null) {
                vehiclesToRemove.add(vehicle);
            }
        }
        vehicles.removeAll(vehiclesToRemove);
        return vehicles;
    }
}