The best tool for "do exactly once" types of tasks that I've found is AtomicBoolean: | private final AtmoicBoolean freed = new AtomicBoolean(false); | | // ...then later, in your idempotent free() method: | if (! freed.getAndSet(true)) { | doTheOneTimeTask(); | } | Of course that's JDK5+ only, so it might not be suitable for things that have to run on older JDKs. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4166529#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...