I need help adding these methods into my code and program. I have provided images of both below.

Modify our Doubly Linked List code to include following index $($rank$)$ based access operations

String retrieveAt$($int index$)$

void deleteAt$($int index$)$

void swap$($int index, int index$)$

index starts at $0($just like array's subscript$)$

If the index is out of bound, retrieveAt returns null, deleteAt does nothing, do nothing in Swap.

Write your own testing program to test the modified class.