Java Uuid Generator (JUG) is a pure java UUID generator, that can be used either as a component in a bigger application, or as a standalone command line tool (similar to Unix 'uuidgen'). UUIDs are 128-bit Universally Unique IDentifiers (aka GUID, Globally Unique IDentifier used in Windows world).
JUG is an open-source library that generates UUIDs according to the IETF UUID specification
(and further clarified in UUID URN name space IETF draft). It specifically supports all 3 'official' types defined by the draft, unlike most (all?) other Java alternatives.
Starting with version 3.0 it will make use of up-to-date JDK features (uses java.util.UUID, can access Ethernet address using feature introduced in 1.6).
For development, GitHub JUG Project Page has all the necessary material (esp. source code).
Discussions are usually handled via Java Uuid Generator Users mailing list at Google-groups.
https://github.com/cowtowncoder/java-uuid-generator/wiki has information on downloads, Maven artifact coordinates.
Documentation page lists existing documentation.
You can use JUG in your application according to AL (Apache License 2.0).