heh.java

    private static Node find(Node oldRoot, Node oldObject, Node newRoot) {
        // Walk down the tree to locate oldObject, and in the process, pick the same child for newRoot
        List<?extends Node> oldChildren = oldRoot.childNodes();
        List<?extends Node> newChildren = newRoot.childNodes();
        Iterator<?extends Node> itOld = oldChildren.iterator();
        Iterator<?extends Node> itNew = newChildren.iterator();

        while (itOld.hasNext()) {
            if (!itNew.hasNext()) {
                return null; // No match - the trees have changed structure
            }

            Node o = itOld.next();
            Node n = itNew.next();

            if (o == oldObject) {
                // Found it!
                return n;
            }

            // Recurse
            Node match = find(o, oldObject, n);

            if (match != null) {
                return match;
            }
        }

        if (itNew.hasNext()) {
            return null; // No match - the trees have changed structure
        }

        return null;
    }

sec.java

    private static Node find(Node oldRoot, Node oldObject, Node newRoot) {
        // Walk down the tree to locate oldObject, and in the process, pick the same child for newRoot
        Iterator<Node> itNew = newRoot.childNodes().iterator();
        
        for (Node o: oldRoot.childNodes()) {
            if (!itNew.hasNext()) return null; // different number of nodes between trees.  mismatch
            
            if (o == oldObject) return itNew.next(); // found location in old tree return new equiv.
            
            Node match = find(o, oldObject, itNew.next());  // depth-first search
            if (match != null) return match;
        }
        
        return null;
    }