question: public void addAll ( @ NonNull List < T > itemList ) { synchronized ( lock ) { if ( items == null ) { items = new ArrayList < > ( ) ; } items . addAll ( itemList ) ; } if ( notifyOnChange ) { if ( items . size ( ) - itemList . size ( ) != 0 ) { notifyItemRangeChanged ( items . size ( ) - itemList . size ( ) , itemList . size ( ) ) ; } else { notifyDataSetChanged ( ) ; } } }
target:  Adds all the specified items to the list