class SdlStorageOfLocal implements SdlStorage {
    private Map<String, String> storage = new HashMap<>();

    /**
     * 更新单点登录标识
     */
    @Override
    public String updateUserSdlKey(Serializable userId) {
        String storageKey = SdlStorage.SESSION_SDL_KEY + ":" + userId;
        String userSdlKey = Utils.guid();

        //设置用户的单点登录标识（当前会话 与 用户的'单点登录标识'，说明当前会话不是最新的登录）
        storage.put(storageKey, userSdlKey);

        return userSdlKey;
    }

    /**
     * 移除单点登录标识
     * */
    @Override
    public void removeUserSdlKey(Serializable userId) {<FILL_FUNCTION_BODY>}

    /**
     * 获取单点登录标识
     */
    @Override
    public String getUserSdlKey(Serializable userId) {
        String storageKey = SdlStorage.SESSION_SDL_KEY + ":" + userId;

        return storage.get(storageKey);
    }
}

        String storageKey = SdlStorage.SESSION_SDL_KEY + ":" + userId;

        storage.remove(storageKey);
    
<no_super_class>