@Override
        public boolean hasNext() {
            if (nextIndex >= items.length) {
                return false;
            }
            if (items[nextIndex] == null) {
                return false;
            }
            return true;
        }
Returns an iterator over the elements of this, starting at the last
element and working backwards. This iterator does not support remove.
vespajlib/src/main/java/com/yahoo/concurrent/ThreadRobustList.java