Question

I’ve been having quite a bit of trouble trying to make a deep copy of a doubly linked list in my java program.

My method thus far is:

public class DblLinkQueue implements Queue {

public Object clone() {
    DblLinkQueue copy = null;
    Node currNode, tmp = null;

    try {
        copy = (DblLinkQueue)super.clone();
    } catch (CloneNotSupportedException err) {}   

    for (currNode = mHead.next; currNode.next != mHead; currNode = currNode.next) {

    }
    System.out.println("i: " + i);
    return copy;
}

}

mHead is the first Node in my list, and this linked list is also circular.

Something is wrong with my for loop because it goes through all the elements in the list, then gets stuck on the last element infinitely.

Any help would be appreciated!

Answer 1

Your loop end condition is that the node prior to the current node is not the head. I’m not sure why you have that in there, and I’m guessing that it’s why you get stuck. Without knowing the design of your Node class, I’d guess that your next member doesn’t throw any sort of iteration exception when there’s no following node, so the loop will go forever (a null Node will never have the same reference value as mHead).