多态 多态注意点

public class asd {

    public static void main(String[] args) {
        Dog dogdog = new Dog();
        Person p = new Person();
        p.f(dogdog);//输出dog

        Animal animaldog = new Dog();
        p.f(animaldog);输出dog

        Animal animalanimal = new Animal();
        p.f(animalanimal);/输出animal
    }
}

class Animal{
    void f(){
        System.out.println("animal");
    }
}
class Person{
    void f(Animal animal){
        animal.f();
    }
}
class Dog extends Animal{
    void f(){
        System.out.println("dog");
    }
}