otr4j is an implementation of the OTR (Off The Record) protocol in java. Its development started during the Google Summer of Code 2009 where the goal was to add support for OTR in jitsi. It currently supports OTRv1, OTRv2 and OTRv3. For a quick introduction on how to use the library have a look at the DummyClient.
If you use maven for managing your project lifecycle and you want to use otr4j in your project, just add the following repository entry to the pom.xml:
IMPORTANT Repository URL has changed !
<repository>
<id>otr4j-repo</id>
<name>otr4j repository on GitHub</name>
<url>http://jitsi.github.com/otr4j/repository/</url>
</repository>