ListNodeIterator.java

 public static void iterateListData(ListNode listNode) {
        ListNode currentList = listNode;
        int nestLevel = 0;
        while (currentList != null ){
            StringBuilder nestIndicator = new StringBuilder("→");
            for (int i = 0; i < nestLevel; i++) {
                nestIndicator.append("→");
            }

            System.out.println(nestIndicator  + " data =  " + currentList.data);
            currentList = currentList.next;
            nestLevel++;
        }

        System.out.println("\n");
    }