code: public synchronized CheckBoxList<V> addItem(V object, boolean checkedState) {
          itemStatus.add(checkedState);
          return super.addItem(object);
      }
docs: Adds an item to the checkbox list with an explicit checked status
  @param object Object to add to the list
  @param checkedState If <code>true</code>, the new item will be initially checked
  @return Itself