is it possible to use swing and html gui elements in one URCap, or is this not a good idea for some reason?
What do I have to pay attention to when using both?
What is the use case for this? I beleive that swing components can do everything that the HTML components could do and a lot more, so I wouls suggest that you just use Swing. Its worth noting that you can use some basic HTML formatting in things like JLabels (to centre text, introduce line breaks, and other tags like <b>, <sup> etc)