关于 hashset 的去重

Question

我定义一个继承关系的类

class Pokemon {

    private String name;
    private int level;
    private int dVS;

    public Pokemon() {
    }

    public Pokemon(String name, int level, int dVS) {
        this.name = name;
        this.level = level;
        this.dVS = dVS;
    }
    

    @Override
    public boolean equals(Object o) {
       ...
    }

    @Override
    public int hashCode() {
        ...
    }
}

class PokemonPearl extends Pokemon{

    public PokemonPearl(String name, int level, int dVS) {
        super(name, level, dVS);
    }
}

class PokemonDiamond extends Pokemon{

    public PokemonDiamond(String name, int level, int dVS) {
        super(name, level, dVS);
    }
}

按照默认重写了 equals() 和 hashCode() 方法，这时候定义子父类的对象，加入到 hashset 里

        Pokemon p4 = new Pokemon("Ralts", 5, 31);
        PokemonPearl p5 = new PokemonPearl("Ralts", 5, 31);
        PokemonDiamond p6 = new PokemonDiamond("Ralts", 5, 31);

        java.util.HashSet<Pokemon> hs = new java.util.HashSet<Pokemon>();

        hs.add(p4);
        hs.add(p5);
        hs.add(p6);

为什么输出不会去重呢，按照逻辑，他们的 哈希值和内容都是相同的啊

Answer 1

不可能啊，我复制的同样的代码，就可以实现啊，你的equals方法或者hashcode方法是不是写错了

@Override
    public int hashCode() {
        return Objects.hash(name,level,dVS);
    }

    @Override
    public String toString() {
        return "Pokemon{" +
                "name='" + name + '\'' +
                ", level=" + level +
                ", dVS=" + dVS +
                '}';
    }

测试类

执行结果