I want to build a tread safe JAVA application which:
VLCJ isn't outdated, it's actively developed and immensely flexible and powerful in what it can achieve. I'm using it in my application to display a number of video streams inside the application at once, as well as doing things such as text overlays simultaneously. It's sometimes tricky to do this, but definitely possible.
There are a number of basic (up-to-date) examples to get you started with VLCJ here.