参数和返回类型也可以多态

class Animala{
    void makeNoise(){
        System.out.println("动物在嘶吼");
    }
}
class Dogs extends Animala{
    void makeNoise(){ //重写
        System.out.println("狗的叫声是汪汪汪");
    }
}
class Cat extends Animala{
    void makeNoise(){
        System.out.println("猫的叫声是喵呜呜呜呜");
    }
}
class Vet{
    public void giveShot(Animala a){
        a.makeNoise();
    }
}
public class Canshufanhui {
    void start(){
        Vet v = new Vet();
        Dogs d = new Dogs();
        Cat c = new Cat();
        v.giveShot(d); //giveshot接受的是animala类型的参数，Dogs继承自animala，利用了参数多态
        v.giveShot(c);
    }
    public static void main(String[] args){
        Canshufanhui p = new Canshufanhui();
        p.start();
    }

}