Java8 lambda expression multiple list fetch intersection

Java8 Previous procedure:

/*** Intersect from a list of values *@paramLists *@return     */     PublicList<object> Intersection (list<list<object>>lists) {        if(Lists = =NULL|| Lists.size () = = 0){            return NULL; } ArrayList<List<Object>> arrayList =NewArraylist<>(lists);  for(inti = 0; I < arraylist.size (); i++) {List<Object> list =Arraylist.get (i); //Remove an empty collection            if(List = =NULL|| List.size () = = 0) {arraylist.remove (list); I-- ; }        }        if(arraylist.size () = = 0){            return NULL; } List<Object> intersection = Arraylist.get (0) ; //There is only one non-empty collection, and the result is that he        if(arraylist.size () = = 1){            returnintersection; }        //There are multiple non-empty collections that intersect directly         for(inti = 1; I < Arraylist.size ()-1; i++) {Intersection.retainall (Arraylist.get (i)); }        returnintersection; }

Stream-style:

 Public Static List<element> retainelementlist (list<list<element>> elementlists) {              Optional<List<Element>> result = Elementlists.parallelstream ()            null & & (List) elementlist. Size ()! = 0)            , {                a.retainall (b);                 return A;        });         return result.orelse (new arraylist<>());    }

Java8 lambda expression multiple list fetch intersection