public SLLNode getByIndex(int index){
            SLLNode current = first;
            int counter = 0;
            while(current != null){
                if(counter == index){
                    return current;
                }
                counter+=1;
                current = current.succ;
            }
            return null;
        }
        public void reverseK(int k){
            SLLNode current = first;
            SLLNode prev = null;
            int counter = 0;
            while(current != null){
                if(counter == k){
                    for(int i = 0; i < k; i++){
                        insertAfter((E) getByIndex(i), prev);
                    }
                }
                counter+=1;
                prev = current;
                current = current.succ;
            }
            current = first;
            counter = 0;
            while(current != null){
                if(counter < k){
                    delete(current);
                }
                counter +=1;
                current = current.succ;
            }
        }