我目前正在尝试使用GoogleGson序列化并正确地反序列化一个包含元组列表的对象。我在这里发现了类似的问题here和here，但我无法调整他们的解决方案来解决我的问题，因为我的列表在一个对象中。
这里有一个简单的例子：

import com.google.gson.*;
import java.util.*;

public class SerializeTheCity  {

    public static void main(String[] args) {

        HashMap <String, Integer> cityMap = new HashMap <>();
        cityMap.put("Street A", 4);
        cityMap.put("Street B", 3);
        cityMap.put("Street C", 7);
        cityMap.put("Street D", 8);
        cityMap.put("Street E", 9);

        City someCity = new City();

        someCity.streets= new ArrayList<>();
        someCity.streets.addAll(cityMap.entrySet());
        System.out.println(someCity.streets.get(1).getValue()); //works fine, how do I serialize it?

        Gson gson = new Gson();

        String saveCity = gson.toJson(someCity);
        System.out.println(saveCity); //does not work (empty List)

        // here I tried to use a solution [link 1] that worked for a similar question.
        Gson gson2 = new Gson();
        JsonElement jsonTree = gson2.toJsonTree(cityMap, Map.class);
        JsonObject jsonObject = new JsonObject();
        jsonObject.add("city", jsonTree);
        System.out.println("city = "+jsonObject); //how do I deserialize this into an object of city?

       City thisCity = gson.fromJson(jsonObject, City.class);
       System.out.println("streets = "+thisCity.streets); // doesnt work

       //works like in [link 1]. But its not a city-object.
       HashMap <String, Integer> thisStreets = gson.fromJson(jsonObject.get("city"), HashMap.class); 
       System.out.println("this streets = "+thisStreets);
       System.out.println("is this street A?"+thisStreets.get("Street A"));
         // this works, but I would like having the streets
        //in a city object (I could build a new city object like "newCity.streets=thisStreets",
        //but perhaps you know a smarter solution)
    }
}
class City { 
    List<Map.Entry<String,Integer>> streets; //Street, HouseNumber
}

谢谢你的帮助。