[grizzles]

The reason are having problems finding info is that most people don't use java clients these days other than android.

You could try teavm.org or gwtproject.org if you really have your heart set on a java client, but I think most people would probably write the client in javascript, probably using react or vue.

If you just want to push the changed data, that sounds like one of the open source operational transform libs on github might be worth looking into.