子类拥有父类非 private 的属性、方法。

package com.example.demo;

import java.util.ArrayList;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        Animal animal=new Animal();
        animal.update();
        Cat cat=new Cat();
        cat.add(new heart(),animal);
        Animal dog=new Dog(new  heart());
        Animal dog1=new Dog(new  heart());
        dog.toString();
        animal.update();

    }


}
class heart{
    protected String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "heart{" +
                "name='" + name + '\'' +
                '}';
    }
}
class Animal {
    public List<heart>  hearts= new ArrayList<heart>();





    @Override
    public String toString() {
        return "Animal{" +
                "hearts=" + hearts +
                '}';
    }
    public void update(){

        System.out.println(hearts.toString());
        for (heart heart:hearts) System.out.println(heart.getName());
    }
}

class Cat  {


    public void add(heart heart,Animal a){
        heart.setName("cay");
        a.hearts.add(heart);
        System.out.println(heart.name);
        System.out.println(a.hearts.toString());
    }

}
class Dog extends Animal{
    public Dog(heart heart) {
        super();
        heart.setName("dog");
        hearts.add(heart);
        toString();
    }

}

[]
cay
[heart{name='cay'}]
[heart{name='cay'}]
cay