HashMap排序算法

package com.itheima.kiki.demo01;
import java.util.*;
/**
 * @author kiki
 * @version 1.0
 * @create 2020/6/4 21:24
 */
/**
 * 对hashmap集合进行排序，按年龄进行倒序排列
 */
public class HashMapTest {
    public static void main(String[] args) {
        //初始化数据
        HashMap<Integer, User> users = new HashMap<>();
        users.put(1,new User("张三",25));
        users.put(2,new User("李四",28));
        users.put(3,new User("王五",22));
        System.out.println(users);
        //调用排序方法
        HashMap<Integer, User> sortHashMap = sortHashMap(users);
        //{2=User{name='李四', age=28}, 1=User{name='张三', age=25}, 3=User{name='王五', age=22}}
        System.out.println(sortHashMap);
    }
    public static HashMap<Integer, User> sortHashMap(HashMap<Integer, User> map){
        //拿到map的键值对集合
        Set<Map.Entry<Integer, User>> entrySet = map.entrySet();
        //转list集合，为了使用Collections的sort方法
        ArrayList<Map.Entry<Integer, User>> list = new ArrayList<Map.Entry<Integer, User>>(entrySet);
        Collections.sort(list, new Comparator<Map.Entry<Integer, User>>() {
            @Override
            public int compare(Map.Entry<Integer, User> o1, Map.Entry<Integer, User> o2) {
                return o2.getValue().getAge()  - o1.getValue().getAge();
            }
        });
        //创建有序的hashmap子类的集合
        LinkedHashMap<Integer, User> linkedHashMap = new LinkedHashMap<>();
        //将list的数据存储到linkedHashMap中
        for (Map.Entry<Integer, User> entry : list) {
            linkedHashMap.put(entry.getKey(),entry.getValue());
        }
        //返回有序的hashmap的子类集合
        return linkedHashMap;
    }
}
class User{
    String name;
    int age;
    public User(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 String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}