I still haven’t seen any good off-the-shelf face recognition solutions for Processing / Java.
Some proprietary systems are now fairly common (e.g. built into phones) but they are generally closed source, full of trade secrets, and based on lots of private training data. Some of the successful techniques involve having information on lots and lots of faces so that you know how your face is different from many others – you can’t make them work well with just an algorithm and some pictures of a few people. Ideally, there would be libraries for beginners with great default training data sets included. I haven’t seem them.
Here are some older discussion of this question from a few years ago and some workshop materials from Face-It, which I believe had some discussion of recognition.
However, note that in general a lot of systems now use a deep learning component to match the detected faces. Detection is comparatively easy; that part is currently still hard to set up and train.