@Override
        public int compare(Message o1, Message o2) {
            String stamp1 = o1.getChildElement("delay", "urn:xmpp:delay").attributeValue("stamp");
            String stamp2 = o2.getChildElement("delay", "urn:xmpp:delay").attributeValue("stamp");
            return stamp1.compareTo(stamp2);
        }
A wrapper for a collection of Message instances that is cached.
xmppserver/src/main/java/org/jivesoftware/openfire/muc/HistoryStrategy.java