Snapshots tend to get built fairly often, they slow down occasionally, but for the most part it happens several times a month.
The following site is useful for keeping things in sync, packages aren't built at the same time usually.. but 90% of the time you won't have any problems, except when libraries in the base get bumped, when that happens it's not a big deal to keep the old packages installed temporarily, if a particular security vulnerability is important to you just build the port manually.
http://www.rhaalovely.net/up2date.html (..unofficial!)
As for Java, no clue, I hate it as much as Flash.
Good luck.