code: public int addItem(final AtomicValue pItem) {
          final int key = mList.size();
          pItem.setNodeKey(key);
          // TODO: +2 is necessary, because key -1 is the NULLDATA
          final int itemKey = (key + 2) * (-1);
          pItem.setNodeKey(itemKey);
  
          mList.add(pItem);
          return itemKey;
      }
docs: Adding to this list.
  
  @param pItem
  setting and item to this list