Question

I’m having trouble understanding the second half of connecting a new node into a double-linked list. I’m writing an add method that takes in the node which the new node is to be inserted after. My area of difficulty is understanding how to link to the next node after the previous node links have been re-directed to the new node.

So, here’s where I’ve come up with

Chunk<E> newChunk= new Chunk<E>();

    newChunk.next= prevChunk.next;
    prevChunk.next= newChunk;

    newChunk.prev= newChunk.next.prev;
    newChunk.next.prev= newChunk;

My understanding is since the newChunk.next= prevChunk.next command copies the memory address of prevChunk.next and sets that value into newChunk.next, and then the prevChunk.next is reset to link to the newChunk.

So since the prevChunk is the only node referenced here that is already in the list, and the next fields have been re-routed to the newChunk, am I on the right track in using those references to link to the next node?

Answer 1

You are correct, but on a side note, most double linked lists are not circular, as the lastNode’s next isn’t the firstNode (same with firstNode’s prev is not the lastNode).
If “prevChunk” were the last Node in the double linked list, and you are adding newChunk after prevChunk as the last item in the linked list,

NewChunk.prev= newChunk.next.prev;

is essentially setting NewChunk’s previous element to null’s previous element, which probably isn’t what you are going for

You might want to check if previous.next initially is null.