I want to use Tracker in Java but I don't see a lot of programming tutorial just Javadocs. I work on a face detection project in videos and I want to calculate face trajectories from coordinates.
I'm sorry, but Tracker is designed to be used with the GUI interface provided, not as a separate library of functions to be called from other Java programs.
On the other hand, all of the Open Source Physics code is open-source and freely downloadable, so you may find it useful to look through the source code for useful classes and/or methods.