public synchronized void setLastPublishedItem(PublishedItem item)
    {
        if ((lastPublished == null) || (item != null) && item.getCreationDate().after(lastPublished.getCreationDate())) {
            Log.trace("Set last published item to: {}", item.getID());
            lastPublished = item;
        }
    }
The last item published to this node.  In a cluster this may have occurred on a different cluster node.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/LeafNode.java