首先，您需要将map.get("label")转换为LinkedTreeMap<Integer, String>，然后使用其值创建新的ArrayList

String json = "{\"countries\":{\"2\":\"China\",\"3\":\"Russia \",\"4\":\"USA\"},\"capitals\":{\"2\":Beijing,\"4\":null,\"3\":Moscow}}";
        HashMap<String,TreeMap<Integer, String>> map = new Gson().fromJson(json, new TypeToken<HashMap<String, TreeMap<Integer, String>>>(){}.getType());
        ArrayList<String> countries = new ArrayList<>(map.get("countries").values());
        System.out.println(countries);

        ArrayList<String> capitals = new ArrayList<>(map.get("capitals").values());
        System.out.println(capitals);

您可以迭代country键集来填充capital数组：

List<String> countries = new ArrayList<>(countriesMap.values());
List<String> capitals = new ArrayList<>();

for (String countryKey : countriesMap.keySet()) {
    capitals.add(capitalsMap.get(countryKey));
}