code: public String getValue(String key) {
          if (onlineProps.containsKey(key))
              return onlineProps.getProperty(key);
          else
              return offlineProps.getProperty(key);
      }
docs: Returns the config value for the specified key or {@code null} if the key
  was not found. If the key is defined in both, the remote and the fallback config,
  the value from the remote config will be returned. If the value is <i>only</i> defined
  in the fallback config but <i>not</i> in the remote config, the local fallback value will
  be returned. (I. e. the remote and fallback config are merged and the remote config is given priority).
  
  @param key The key of the config parameter.
  @return the config value for the specified key or {@code null} if the key
  was not found.