public class BubbleSwapList<E>  {
    private class Node<E> { 
        public final E element; 
        public Node<E> next; 
        public Node<E> previous; 
        public Node(E element) {
            this.element = element; 
            this.next = null; this.previous = null; 
            }
        }
        private Node<E> head;
        public BubbleSwapList() { 
            head = null;  
        }
        public void add(E element) {
            Node<E> toAdd = new Node<E>(element); 
            if (head != null) 
                head.previous=toAdd; 
            toAdd.next = head;
            head = toAdd; 
        }
        public String toString() {
            StringBuilder sb = new StringBuilder();
            sb.append("[ ");
            Node<E> curr = head;
            while (curr!=null) {
                sb.append(curr.element);
                sb.append(" ");
                curr=curr.next;
            }
            sb.append("]");
            return sb.toString();
        }
        public void bubble(E e) {
            Node<E> curr = head;
            while (!curr.element.equals(e)) {
                curr=curr.next;
            }
            if (curr==null) {
                return;
            }
            // want to swap curr with curr.next;
            if (curr.next==null) {
                return;
            }
            Node<E> nxt = curr.next;
            if (nxt.next !=null) {
                nxt.next.previous=curr;
            }
            if (curr.previous!=null) {
                curr.previous.next = nxt;
            }
            curr.next = nxt.next;
            nxt.next = curr;
            nxt.previous=curr.previous;
            curr.previous=nxt;
            if (curr==head)
                head=nxt;
        }


        public static void main(String[] args) {
            BubbleSwapList<Integer> bsl = new BubbleSwapList<>();
            for (int i=0; i<10; i++)
                bsl.add(i);
            System.out.println(bsl);
            bsl.bubble(9);
            System.out.println(bsl);
        }
    }