hashCode方法 和 equals()方法

package com.coding.spring.mvc;

import java.util.HashSet;

public class User {
    private String name;

    public User(String name) {
        this.name = name;
    }

    @Override
    public boolean equals(Object obj) {
        User user = (User) obj;
        return name.equals(user.name);
    }

    // 注意 hashCode方法 和  equals()方法必须同时重写才可以
    @Override
    public int hashCode() {
        return name.hashCode();
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                '}';
    }

    public static void main(String[] args) {
        HashSet<User> users = new HashSet<>();

        User tom1 = new User("tom");
        User tom2 = new User("jack");
        User tom3 = new User("tom");

        users.add(tom1);
        users.add(tom2);
        users.add(tom3);

        users.forEach((item) -> {
            System.out.println(item);
        });
        // output: User{name='tom'}
        //       User{name='jack'}
    }
}
~~~java