@Override
    public void stop() {
        // Clear the caches when stopping the module.
        offlinePresenceCache.clear();
        lastActivityCache.clear();
        // Stop listening for user deletion events
        UserEventDispatcher.removeListener(this);
    }
Simple in memory implementation of the PresenceManager interface.

@author Iain Shigeoka
xmppserver/src/main/java/org/jivesoftware/openfire/spi/PresenceManagerImpl.java