LightCarContainer.java

public class LightCarContainer {

    private static HashMap<String,LightCar> lightCars = new HashMap<String, LightCar>();
    
    public static LightCar getLightCar(String engine, String color) {
        String key = engine + color;
        if (!lightCars.containsKey(key)) {
            lightCars.put(key, new LightCar(engine,color));
        }
        return lightCars.get(key);
    }
}