java集合HashSet

jdk1.8之前：数组+链表
jdk1.8及之后：数组+链表+红黑树

假设：底层是一个数组，数组长度是8，每个储存的数据，根据计算对应的hashCode然后再计算对应的索引，
每个下标中存放的其实是一个链表，然后就调用equlas方法，比较数据是否在此链表中重复，重复的话不储存
不重复就添加到尾部
【在jdk1.8之后，当数组中某一个索引下对应的链表长度过长，不利于查找时候，会自动转换为红黑树储存】

import java.util.HashSet;
import java.util.Objects;

public class Class005_hashSet {
    public static void main(String[] args) {
        HashSet psons = new HashSet<>();
        psons.add(new Person002("zhangsan",18));
        psons.add(new Person002("zhangsan",19));
        psons.add(new Person002("zhangsan",18));
        for (Person002 pson : psons) {
            System.out.println(pson);
        }
    }
}
class Person002{
    private String name;
    private int    age;

    public Person002() {
    }

    public Person002(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        Person002 person = (Person002) o;
        return age == person.age &&
                Objects.equals(name, person.name);
    }

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

    @Override
    public String toString() {
        return "Person002{" +
                "name='" + name + ''' +
                ", age=" + age +
                '}';
    }
}