https://blog.csdn.net/weixin_57204093/article/details/129791857

package com.qf.b_hashSet;
 
import java.util.HashSet;
import java.util.Set;
 
class Person {
    int id;
    String name;
    public Person(int id, String name) {
        
        this.id = id;
        this.name = name;
    }
    @Override
    public String toString() {
        return "Person [id=" + id + ", name=" + name + "]";
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + id;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Person other = (Person) obj;
        if (id != other.id)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }
    
    
}
public class Demo2 {
    public static void main(String[] args) {
        
        Set<Person> set = new HashSet<Person>();
        Person person1 = new Person(1, "黑龙");
        Person person2 = new Person(2, "花花");
        Person person3 = new Person(1, "黑龙");
        set.add(person1);
        set.add(person2);
        set.add(person3);
        System.out.println(set);
        //现在存了三个对象。
        //重写equlas和hashCode方法
    }
}

总结： 如果将对象存入到hashSet中的时候，必须重写当前类的equals和hashCode方法 为了保证对象的内容不重复。