...
> I have to create a wysiwyg editor in Java (like a little word).
...
> - I must be able to add constraints over tables for example to indicate that
> one cell is enabled only if another cell has a particular value.
Only limited by your skill.
> - if I use something existing, I must have the source code.
The PhySci software project has a rudimentary text editor
('A' Pad) that might give you a start, you can install it here..
http://www.physci.org/install/download.htm
And download the .jar (which contains the full source), here..
http://www.physci.org/PhySci.jar
HTH
--
Andrew Thompson
http://www.AThompson.info/
http://www.PhySci.org/
http://www.1point1C.org/