I would say no for a java chat room.
It would slooooww down the site, and there is no point of reloading a site just to get into a chat.
I would say yes to an chat room if it was either IRC, or a standalone java application. But then it should be able to do things like, icons. And most of all be able to send files.
So for no to java chat room.
Yes to IRC chat room.