scjp考试准备 - 9

abstract class Vehicle{
    public int speed(){
        return 0;
    }
}

class Car extends Vehicle{
    public int speed(){
        return 60;
    }
}

class RacerCar extends Car{
    public int speed(){
        return 150;
    }
    
    public void run(){
        System.out.println("I‘m running...");
    }
}

public class Test{
    public static void main(String[] args){
        RacerCar racer = new RacerCar();
        Car car = new RacerCar(); 
        Vehicle vehicle = new RacerCar(); 
        System.out.println(racer.speed() + ", " + car.speed()  + ", " + vehicle.speed()); 
    }
}