> first question: how do you delete posts?
You don't. You update the old posting with a link to the new discussion.
> second, how do i put a plaindocument on a jformattedtextfield?
Well, I would think it already uses a PlainDocument. A PlainDocument simply means you can't use different fonts and colors in the Document since it ignores attributes.
Assuming it doesn't then, the obvious would be:
setDocument(...);
If that doesn't work then JFormattedTextField probably prevents this for some reason.
Maybe if you explained what you are attempting to do another suggestion can be made.