code: public void undo() {
      if (isListChange()) {
        LOGGER.trace("Undoing list change: " + oldList.get().toString());
        setting.valueProperty().setValue(oldList.get());
      } else {
        setting.valueProperty().setValue(oldValue.get());
      }
    }
docs: Undos a change.
  Does this by setting the corresponding value of the {@link Setting} to the old value of this
  change.