When it comes to online or desktop presentation we've options like actionscript, java, picolo, flare, prefuse. Now choosing a perfect language for needs is subjective and depends on project. But if you've to choose Processing (language), then on what basis you'll choose? what are the pro's and con's of processing in your opinion?
Processing makes it (relatively) easy to visualize data. The website gives some hints about where / who is using it:
Processing is an open source programming language and environment for people who want to program images, animation, and interactions. It is used by students, artists, designers, researchers, and hobbyists for learning, prototyping, and production. It is created to teach fundamentals of computer programming within a visual context and to serve as a software sketchbook and professional production tool. Processing is an alternative to proprietary software tools in the same domain.
Look around on the website for demos, case studies and more information.
In my opinion, it is good if you want to draw graphics or even animations in a simple way, but it is not very well suited for programming GUIs.
In my opinion, Processing is a great tool for data visualization applications (things like this: http://www.visualcomplexity.com/vc/). I've used in the past for such purpose, to display the difference between graph drawing algorithms.
It's definitely not a general purpose language, but I think it might be able to integrate it with Java.