I need a free forum with java support

phpBB is easy enough to install and quite popular. But I think the forum feature is being added to other CMS (or content management system) software. Although I'm not sure about it, it may even be part of WordPress by now because as far as I know, it's been included in Drupal for quite some time. Anyway, in my opinion, phpBB will be a good stand-alone forum while other popular CMS may offer better integration of the forum feature.

Depends on what kind of forum you want. InvisionBoard, phpBB...but I'd recommend Simple Machines. It's free and looks really nice. Not sure about the java support or Facebook integration though.