Let's write a test program:
public static void main(String... arg) { double timeSec = 10.0; int engineHorsePower = 246; int vehicleWeightPounds = 4000; Vehicle vehicle = new Car(4, vehicleWeightPounds, engineHorsePower); System.out.println("Passengers count=" + ((Car)vehicle).getPassengersCount()); System.out.println("Car speed (" + timeSec + " sec) = " + vehicle.getSpeedMph(timeSec) + " mph"); vehicle = new Truck(3300, vehicleWeightPounds, engineHorsePower); System.out.println("Payload=" + ((Truck)vehicle).getPayload() + " pounds"); System.out.println("Truck speed (" + timeSec + " sec) = " + vehicle.getSpeedMph(timeSec) + " mph");}
Notice that the vehicle reference of the Vehicle type points to the object of the Car
