关于java里面的list数据如何分组？

//list包装的实体类
List userList = new ArrayList<>();
User user = new User();
user.setName("张三");
user.setHeight("168");
user.setSex("男");
userList.add(user);
userList.add(user);
user.setName("小张");
user.setHeight("169");
user.setSex("女");
userList.add(user);
userList.add(user);

//list包装的实体类按照性别分组
Map> listMap = userList.stream().collect(Collectors.groupingBy(user1 -> user.getSex()));

//list包装的实体类按照性别加姓名分组分组
Map> listMap2 = userList.stream().collect(Collectors.groupingBy(user1 -> user.getSex() + user1.getName()));

//list包装的map
List> userMaps = new ArrayList<>();
Map map = new HashMap<>();
map.put("name", "张三");
map.put("height", "168");
map.put("sex", "男");
userMaps.add(map);
userMaps.add(map);
map.put("name", "小张");
map.put("height", "169");
map.put("sex", "女");
userMaps.add(map);
userMaps.add(map);

//list包装的map按照性别分组
Map>> listMap3 = userMaps.stream().collect(Collectors.groupingBy((Map map1) -> (String) map.get("sex")));

//list包装的实体类按照性别加姓名分组分组
Map>> listMap4 = userMaps.stream().collect(Collectors.groupingBy(
        (Map map1) -> (String) map.get("sex") + (String) map.get("name")));

//JSONArray
JSONArray jsonArray = new JSONArray();
JSONObject json = new JSONObject();
json.put("name", "张三");
json.put("height", "168");
json.put("sex", "男");
jsonArray.add(json);
jsonArray.add(json);
json.put("name", "小张");
json.put("height", "169");
json.put("sex", "女");
jsonArray.add(json);
jsonArray.add(json);

//JSONArray包装的JSONObject按照性别分组
Map> listMap5 = jsonArray.stream().collect(Collectors.groupingBy(jsonObject ->
        ((JSONObject)jsonObject).getSring("name"), Collectors.mapping(jsonObject -> (JSONObject)jsonObject, Collectors.toList())));