Java中 接口是如何实现多态的特性的

//汽车接口
interface Car{
    //要求 接口中有：汽车名称和售价
    
    String getName();
    int getPrice();
    
}

//宝马类
class BMW implements Car{

    @Override
    public String getName() {
        // TODO Auto-generated method stub
        //return null;
        return "宝马";
    }

    @Override
    public int getPrice() {
        // TODO Auto-generated method stub
        //return 0;
        return 300000;
    }
    
}

//奇瑞QQ
class CheryQQ implements Car{

    @Override
    public String getName() {
        // TODO Auto-generated method stub
        return "奇瑞QQ";
    }

    @Override
    public int getPrice() {
        // TODO Auto-generated method stub
        return 40000;
    }
    
}

//汽车出售店
class CarShop{
    //收入
    private int money=0;
    
    //卖出一部汽车
    public void sellCar(Car car){
        System.out.println("车型："+car.getName()+"价格："+car.getPrice());
        //增加卖出车售价的收入
        money+=car.getPrice();
    }
    //售车总收入
    public int getMoney(){
        return money;
    }
}

public class jieKouDemo {
    public static void main(String[]args){
        CarShop shop=new CarShop();
        //卖出一辆宝马
        shop.sellCar(new BMW());
        //卖出一辆奇瑞QQ
        shop.sellCar(new CheryQQ());
        
        System.out.println("总收入："+shop.getMoney());
    }

}