怎么根据行政区代码将数据转化成树结构？

将数据表查询的数据，转成这个格式的json

你的数据量只有两列吗

/**
 * 递归省市区
 * @author XMF
 * @date 2021-05-25 16:15
 **/
public class Demo {
    public static void main1(String[] args) {

        System.out.println(System.currentTimeMillis());
       List<City> cityList = new ArrayList<>();
       cityList.add(new City(1, 0, "北京", "北京"));
       cityList.add(new City(2, 0, "内蒙", "内蒙"));
       cityList.add(new City(3, 0, "河北", "河北"));

       cityList.add(new City(11, 1, "东城", "北京东城"));
       cityList.add(new City(12, 2, "呼市", "内蒙新呼市"));
       cityList.add(new City(13, 3, "唐山", "河北唐山"));
       cityList.add(new City(14, 1, "西城", "北京西城"));

       cityList.add(new City(21, 11, "南锣鼓巷", "北京东城南锣鼓巷"));
       cityList.add(new City(22, 12, "新城区", "内蒙新呼市新城区"));
       cityList.add(new City(23, 13, "哈哈区", "河北唐山哈哈区"));
       cityList.add(new City(24, 11, "南洛惜香", "北京东城南洛惜香"));
       cityList.add(new City(25, 14, "西城广场", "北京西城西城广场"));

        List<City> collect = cityList.parallelStream().filter(g -> g.getParentId() == 0).collect(Collectors.toList());

        System.out.println(JSON.toJSONString(getData(collect, cityList, cityList, 0)));

        System.out.println(System.currentTimeMillis());
    }

    public static List<City> getData(List<City> list, List<City> cityList, List<City> cityOldList, int status){
        for (City city : list) {
                cityList = cityOldList.parallelStream().filter(f -> f.getParentId() == city.getId()).collect(Collectors.toList());
                if (!cityList.isEmpty()){
                    if (city.getChilds() ==null){
                        city.setChilds(new ArrayList<>());
                    }
                    city.setChilds(cityList);
                    getData(cityList, cityOldList, cityOldList, 1);
                }
        }
        return list;
    }


    public static void main(String[] args) {
        System.out.println(System.currentTimeMillis());
        List<City> cityList = new ArrayList<>();
        cityList.add(new City(1, 0, "北京", "北京"));
        cityList.add(new City(2, 0, "内蒙", "内蒙"));
        cityList.add(new City(3, 0, "河北", "河北"));
        cityList.add(new City(11, 1, "东城", "北京东城"));
        cityList.add(new City(12, 2, "呼市", "内蒙新呼市"));
        cityList.add(new City(14, 1, "西城", "北京西城"));
        cityList.add(new City(13, 3, "唐山", "河北唐山"));
        cityList.add(new City(21, 11, "南锣鼓巷", "北京东城南锣鼓巷"));
        cityList.add(new City(23, 13, "哈哈区", "河北唐山哈哈区"));
        cityList.add(new City(22, 12, "新城区", "内蒙新呼市新城区"));
        cityList.add(new City(24, 11, "南洛惜香", "北京东城南洛惜香"));
        cityList.add(new City(25, 14, "西城广场", "北京西城西城广场"));

        for (int a = 0; a < 20; a ++){
            System.out.println(cityList.parallelStream().findAny());
        }




        Map<Integer, List<City>> resultMap1 = cityList.stream().collect(Collectors.groupingBy(City::getParentId, Collectors.toList()))
                .entrySet().stream().sorted(Map.Entry.comparingByKey())
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (a, b) -> b, LinkedHashMap::new));
        resultMap1.entrySet().forEach(System.out::println);
        System.out.println("------------");
        Map<Integer, List<City>> resultMap = cityList.stream().collect(Collectors.groupingBy(City::getParentId, Collectors.toList()))
                .entrySet().stream().sorted(Collections.reverseOrder(Map.Entry.comparingByKey()))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (a, b) -> b, LinkedHashMap::new));

        resultMap.entrySet().forEach(System.out::println);
//        List<Integer> collect = mapCommodity 排序
//                .entrySet()
//                .stream()
//                .sorted(Collections.reverseOrder(Map.Entry.comparingByValue()))
//                .map(Map.Entry::getKey).collect(Collectors.toList());
//                            .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e2,
//                                            LinkedHashMap::new));


//        List<City> sheng = cityList.stream().filter(f -> f.getParentId() == 0).collect(Collectors.toList());
//        sheng.forEach(s -> {
//            List<City> list = resultMap.get(s.getId());
//            s.setChilds(list);
//            list.forEach(l -> {
//                List<City> list1 = resultMap.get(l.getId());
//                l.setChilds(list1);
//            });
//        });


        //parentId 分组
//        Map<Integer, List<City>> resultMap = new HashMap<>();

//        Map<Integer, List<City>> collect = resultMap.entrySet().stream().sorted(Collections.reverseOrder(Map.Entry.comparingByKey())).collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (a, b) -> b));
//
//        for (City city : cityList) {
//            if(resultMap.containsKey(city.getParentId())){
//                resultMap.get(city.getParentId()).add(city);
//            }else{
//                List<City> newList=new ArrayList<>();
//                newList.add(city);
//                resultMap.put(city.getParentId(), newList);
//            }
//        }
//        //获取所有省
//        List<City> sheng = new ArrayList<>();
//        for (City city : cityList) {
//            if(city.getParentId() == 0){
//                sheng.add(city);
//            }
//        }
//
//        for (City city : sheng) {
//            //省对应市
//            List<City> shi = resultMap.get(city.getId());
//            city.setChilds(shi);
//            for (City city1 : shi) {
//                List<City> cities = resultMap.get(city1.getId());
//                city1.setChilds(cities);
//            }
//        }
//
//
//        System.out.println(JSON.toJSONString(sheng));
//        System.out.println(System.currentTimeMillis());



    }
}
@Data
class City{

    private int id, parentId;
    private String cityName, cityAllName;
    private List<City> childs;

    public City(int id, int parentId, String cityName, String cityAllName){
        this.id = id;
        this.parentId = parentId;
        this.cityAllName = cityAllName;
        this.cityName = cityName;
    }
}

这是我原先写的类似的省市区树状数据，有看看有思路没