Java Programming

Could someone explain to me please the best techniques for code folding?
I know what it is obviously, and what it does, however I'm trying to write my own program using code folding and hitting a big problem with it.

I have found the Bounce XMLEditorKit which is great but the code folding doesn't work (at least I can't get it to work) so that doesn't help.
I can use the netbeans platform but I'd firstly rather have an entirely custom written app, plus I don't really like the creation process. (Don't understand it fully as well)

So how do I go about it myself?


I know I need to determine fold points (thinking syntax based as it will be XML documents)
Where I get confused is how to keep track. Once I've determined where a fold starts and ends, say I minimize the code replacing it with a ... and put the replaced code in a variable. This is fine, but if code is then added to the program before this fold line, how do I keep track of where it now is, so I know where to open the fold?

Basically, could someone give me the entire logic behind code folding? Or an easy to implement ready made solution


Thanks
Adrian