如何对对象中的子HashMap进行排序

import java.util.*;

public class SortHashMap {
    public static void main(String[] args) {
        // 创建包含子HashMap的对象
        Map<String, HashMap<String, Integer>> obj = new HashMap<>();
        HashMap<String, Integer> subMap = new HashMap<>();
        subMap.put("key1", 3);
        subMap.put("key2", 1);
        subMap.put("key3", 2);
        obj.put("subHashMap", subMap);

        // 将子HashMap转换为List
        List<Map.Entry<String, Integer>> list = new ArrayList<>(subMap.entrySet());

        // 对List进行排序
        Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {
            @Override
            public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
                // 按照键进行升序排序
                return o1.getKey().compareTo(o2.getKey());
            }
        });

        // 将排序后的List转换回HashMap
        HashMap<String, Integer> sortedSubMap = new LinkedHashMap<>();
        for (Map.Entry<String, Integer> entry : list) {
            sortedSubMap.put(entry.getKey(), entry.getValue());
        }

        // 更新对象中的子HashMap
        obj.put("subHashMap", sortedSubMap);

        System.out.println(obj);
    }
}