Map的entrySet实现map按key升序排列或value降序排列

TreeMap<Integer, Integer>按key升序排列

TreeMap<Integer, Integer>按value降序排列

package MapTest;

import java.util.*;

public class Map4 {
    
    public static void main(String[] args) {
    

        TreeMap<Integer, Integer> treeMap = new TreeMap<>();
        treeMap.put(1, 310);
        treeMap.put(3, 310);
        treeMap.put(4, 539);
        treeMap.put(2, 420);
        ArrayList<Map.Entry<Integer, Integer>> list = new ArrayList<>(treeMap.entrySet());

        //按key升序排列
        Collections.sort(list, new Comparator<Map.Entry<Integer, Integer>>() {
    
            @Override
            public int compare(Map.Entry<Integer, Integer> o1, Map.Entry<Integer, Integer> o2) {
    
                //o1-o2升序排列
                return o1.getKey() - o2.getKey();
            }
        });

        for (Map.Entry<Integer, Integer> entry : list) {
    
            System.out.println(entry.getKey() + " " + entry.getValue());
        }
        System.out.println();
        //按value降序排列
        Collections.sort(list, new Comparator<Map.Entry<Integer, Integer>>() {
    
            @Override
            public int compare(Map.Entry<Integer, Integer> o1, Map.Entry<Integer, Integer> o2) {
    
                //o2-o1降序排列
                return o2.getValue() - o1.getValue();
            }
        });

        for (Map.Entry<Integer, Integer> entry : list) {
    
            System.out.println(entry.getKey() + " " + entry.getValue());
        }
    }
}

Map<Integer, String[]>按照key升序排列

package MapTest;

import java.util.*;
//按照key升序排列
public class Map4 {
    
    public static void main(String[] args) {
    
        HashMap<Integer, String[]> map = new HashMap<>();
        map.put(1, new String[]{
    "4536117005899"});
        map.put(3, new String[]{
    "3424342341666"});
        map.put(4, new String[]{
    "5536117001860"});
        map.put(2, new String[]{
    "2022032600001", "2022032600002", "2022032600003"});

        ArrayList<Map.Entry<Integer, String[]>> list = new ArrayList<>(map.entrySet());
        //按key升序排列
        Collections.sort(list, new Comparator<Map.Entry<Integer, String[]>>() {
    
            @Override
            public int compare(Map.Entry<Integer, String[]> o1, Map.Entry<Integer, String[]> o2) {
    
                //o1-o2升序排列
                return o1.getKey() - o2.getKey();
            }
        });

        for (Map.Entry<Integer, String[]> entry : list) {
    
            System.out.println(entry.getKey() + " " + Arrays.toString(entry.getValue()));
        }

    }
}

Map<String, String>按照value升序排列

package MapTest;

import java.util.*;

//## Map<String, String>按照value升序排列
public class Map5 {
    
    public static void main(String[] args) {
    
        Map<String, String> map = new HashMap<String, String>();
        map.put("b", "4");
        map.put("a", "5");
        map.put("c", "3");
        map.put("d", "5");

        //将map<String,String> 转化为ArryList,但list里面的元素为Entry<String,String>
        List<Map.Entry<String, String>> list = new ArrayList<Map.Entry<String, String>>(map.entrySet());
        Collections.sort(list, new Comparator<Map.Entry<String, String>>() {
    
            @Override
            public int compare(Map.Entry<String, String> o1, Map.Entry<String, String> o2) {
    
                //升序排列
                int flag = o1.getValue().compareTo(o2.getValue());
                //value相等
                if (flag == 0) {
    
                    return o1.getKey().compareTo(o2.getKey());
                }
                return flag;
            }
        });
        //遍历list得到map里面排序后的元素
        for (Map.Entry<String, String> en : list) {
    
            System.out.println(en.getKey() + " " + en.getValue());
        }
    }
}