java - 如何将 Java 对象列表转换为 Map>

Question

我有一个 Java 对象列表，如下所示:

[
  {
    id: "frwfhfijvfhviufhbviufg",
    country_code: "DE",
    message_key: "key1",
    translation: "This is the deutsch translation"
  },
  {
    id: "dfregregtegetgetgttegt",
    country_code: "GB",
    message_key: "key1",
    translation: "This is the uk translation"
  },
  {
    id: "frffgfbgbgbgbgbgbgbgbg",
    country_code: "DE",
    message_key: "key2",
    translation: "This is the again deutch translation"
  }
]

我怎样才能把它转换成 Map<String, Map<String, String>>像下面这样:

{
  "DE": {
    "key1": "This is the deutsch translation",
    "key2": "This is the again deutch translation"
  },
  "GB": {
    "key1": "This is the uk translation"
  }
}

我是 Java 新手，下面是我的代码，但代码不正确:

Map<String, Translations> distinctTranslations = customTranslationsEntities
        .stream().collect(Collectors.groupingBy(
                CustomTranslationsEntity::getCountryCode,
                Collectors.toMap(
                        CustomTranslationsEntity::getMessageKey,
                        CustomTranslationsEntity::getTranslation),

                )))

其中 Translations 是 proto 缓冲区消息，如下所示:

message Translations {
  map<string, string> translations = 1;
}

这里 map<string, string> translations意味着像 "key1", "This is the deutsch translation" 这样的 map ...像这样。

Answer 1

输出应该是 Map<String, Map<String,String>> :

Map<String, Map<String,String>>
    distinctTranslations = customTranslationsEntities
            .stream()
            .collect(Collectors.groupingBy(CustomTranslationsEntity::getCountryCode,
                                    Collectors.toMap(
                                            CustomTranslationsEntity::getMessageKey,
                                            CustomTranslationsEntity::getTranslation,
                                            (v1,v2)->v1)));

我添加了一个合并功能，以防有重复的键。