"dward" wrote : I don't see how using ConcurrentHashMap would be any different than Collections.synchronizedMap(new HashMap()) In answer to this part, the difference is in the enforced synchronization for readers. With ConcurrentHashMap you can have multiple readers accessing the map concurrently. This may not be such a big difference on some machines but why have a synchronization point when you don't need it? Kev View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4269527#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...