code: public static void doSetNullIsFirstRecursively(ComparatorItem comparatorItem,
        boolean nullIsFirst) {
      ComparatorItem tmp = comparatorItem;
      while (tmp != null) {
        tmp.setNullIsFirst(nullIsFirst);
        tmp = tmp.getNextComparatorItem();
      }
    }
docs: Sets the sort order of a null value to all items.
  
  @param comparatorItem the (root) item
  @param nullIsFirst    {@code true} if the sort order of a null value is higher than a non-null
  value, otherwise {@code false}