java/w6/Animal.java

abstract class Animal {
    public abstract void makesound();
}
interface Swimmable{
    void swim();
}
class Dog extends Animal implements Swimmable{
    @Override
    public void makesound(){
        System.out.println("汪汪汪");
    }
    @Override
    public void swim(){
        System.out.println("狗刨游泳");
    }
}
class Cat extends Animal{
    @Override
    public void makesound(){
        System.out.println("喵喵喵");
    }
}
class Main{
    public static void main(String[]args){
        Animal a =new Dog();
        Animal b =new Cat();
        a.makesound();
        b.makesound();
        if (a instanceof Swimmable){
            ((Swimmable)a).swim();
        }
    }
}