Question

如何按关键字对地图进行排序？

我的地图结构是这样的

Map<String, List<Mobile>> mobiles = new HashMap<String, List<Mobile>>();

mobiles.put("Samsung", ListOfMobileModels);
mobiles.put("Nokia", ListOfMobileModels);
mobiles.put("Apple", ListOfMobileModels);
mobiles.put("Blackberrey", ListOfMobileModels);

/** Sort Like below**/

mobiles.put("Apple", ListOfMobileModels);
mobiles.put("Blackberrey", ListOfMobileModels);
mobiles.put("Samsung", ListOfMobileModels);
mobiles.put("Nokia", ListOfMobileModels);

我在另一个地图（例如Apple-1，Blackberry-2，Samsung-3，Nokia-4）中有移动排名列表

如何使用流或任何比较器对地图进行排序？

Answer 1

看看这个例子：

SortedMap<String, String> fileExtensions  = new TreeMap<>();

        // Adding new key-value pairs to a TreeMap
        fileExtensions.put("python", ".py");
        fileExtensions.put("c++", ".cpp");
        fileExtensions.put("kotlin", ".kt");
        fileExtensions.put("golang", ".go");
        fileExtensions.put("java", ".java");

        // Printing the TreeMap (Output will be sorted based on keys)
        System.out.println(fileExtensions);
    }

似乎是您要寻找的。 Source

基于此，您可以创建一个Enum和一个类Comparator：

import java.util.*;

public class Main2 {
    public static void main(String[] args) {
        SortedMap<RankComparator,List<Mobile>> mobiles = new TreeMap<>();

        List<Mobile> mobiles1 = new ArrayList<>();

        mobiles.put(new RankComparator(Rank.Samsung), mobiles1);
        mobiles.put(new RankComparator(Rank.Nokia), mobiles1);
        mobiles.put(new RankComparator(Rank.Apple), mobiles1);
        mobiles.put(new RankComparator(Rank.Blackberry), mobiles1);

        ((TreeMap<RankComparator, List<Mobile>>) mobiles).entrySet().forEach(e -> System.out.println(e.getKey().rank));
    }
}

class Mobile{
    Rank rank;

    public Mobile(Rank rank) {
        this.rank = rank;
    }
}

enum Rank{
    Apple(1),
    Blackberry(2),
    Samsung(3),
    Nokia(4);

    int rank;
    Rank(int i) {
        this.rank = i;
    }
}

class RankComparator implements Comparable<RankComparator>{

    Rank rank;

    public RankComparator(Rank rank) {
        this.rank = rank;
    }

    @Override
    public int compareTo(RankComparator otherRank) {
        return this.rank.rank - otherRank.rank.rank;
    }
}

输出->

Apple
Blackberry
Samsung
Nokia

使用Stream的Java8地图排序

1 个答案: