OneTrickPony is a modern Java library that implements support for One-Time Passwords. Built-In support is provided for the HOTP (RFC 4226) and TOTP (RFC 6238) algorithms.
Since this library is rather small, decently tested, and no issues were found during dogfooding, there will be a 1.0.0 release soon to properly reflect the API status. I do not expect any API changes but this is a good time to go over the documentation and make sure that everything is written in a consistent tone.