Map集合根据value排序_map集合怎么根据value排序-优快云博客

本文介绍了如何在Java中使用TreeMap类，并配合Comparator接口，以等级为依据对Roll对象进行排序。实例展示了如何创建TreeMap、添加元素并按照Roll对象的level属性进行降序排序。

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package test.maps;

import test.collections.Occupation;
import test.collections.Roll;

import java.util.*;

public class TreeMapTest {
    public static void main(String[] args) {
        TreeMap<Integer, Roll> treeMap = new TreeMap<>();
        Roll roll1 = new Roll(1, Occupation.武士, "一点寒芒");
        Roll roll2 = new Roll(15, Occupation.文人, "文文文");
        Roll roll3 = new Roll(1, Occupation.异人, "毁天灭地");
        Roll roll4 = new Roll(160, Occupation.武士, "一刀999");
        treeMap.put(1, roll1);
        treeMap.put(4, roll2);
        treeMap.put(3, roll3);
        treeMap.put(2, roll4);


        //treeSet根据value排序
        //1. 先获取键值对set
        Set<Map.Entry<Integer,Roll>> entries =  treeMap.entrySet();
        //2. 再转为List
        List<Map.Entry<Integer,Roll>> list = new ArrayList<>(entries);
        //3. 传入比较器进行排序
        list.sort(new Comparator<Map.Entry<Integer, Roll>>() {
            @Override
            public int compare(Map.Entry<Integer, Roll> o1, Map.Entry<Integer, Roll> o2) {
                return o1.getValue().compareTo(o2.getValue());
            }
        });


        for (Map.Entry<Integer,Roll> entry: list
             ) {
            System.out.println(entry);
        }
    }

}

package test.collections;

import java.util.Comparator;
import java.util.Objects;

public class Roll implements Comparable<Roll> {
    //等级
    private int level;
    //职业
    private Occupation occupation;
    //姓名
    private String name = null;

    public Roll(int level, Occupation occupation) {
        this.level = level;
        this.occupation = occupation;
    }

    public Roll(int level, Occupation occupation, String name) {
        this.level = level;
        this.occupation = occupation;
        this.name = name;
    }

    public int getLevel() {
        return level;
    }

    public void setLevel(int level) {
        this.level = level;
    }

    public Occupation getOccupation() {
        return occupation;
    }

    public void setOccupation(Occupation occupation) {
        this.occupation = occupation;
    }

    public String getName() {
        return name;
    }

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

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

    @Override
    public int compareTo(Roll o) {
        return o.level - this.level;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Roll roll)) return false;
        return level == roll.level && occupation == roll.occupation && Objects.equals(name, roll.name);
    }

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

https://blog.youkuaiyun.com/xHibiki/article/details/82938480