For anyone still looking for a library with examples, there is a library written in Kotlin which can be used in Java projects:

https://github.com/bitfireAT/dav4jvm

I've created a sample Java project available at

https://github.com/richteas75/DavExample

to demonstrate obtaining calendars from a CalDav server using server url, username and password.
The code is basically adapted from the Kotlin code of the DAVx5 app, mainly DavResourceFinder.kt.