code: public final void update (final OperationalTextKey textKey, final String newTextValue, final IResultFunction resultFunction) {
  
          final String oldValue = settingsMap.get(textKey);
  
          String updatedValue;
          if (oldValue == null) {
              if (LOGGER.isWarnEnabled()) {
                  LOGGER.warn("Update old value failed: No old value for key " + textKey.value() + ".");
              }
  
              updatedValue = newTextValue;
          } else {
              updatedValue = resultFunction.result(oldValue, newTextValue);
          }
  
          settingsMap.put(textKey, updatedValue);
      }
docs: Update the stored value with the given one. The result is dependant on the <code>IResultFunction</code> instance.
  
  @param textKey The <code>OperationalTextKey</code> to update.
  @param newTextValue The new value, which is interpreted as response.
  @param resultFunction The <code>IResultFunction</code> to use to obtaining the result.