UDDI4J is a Java class library that provides an API that is can be used to interact with a UDDI registry. This class library generates and parses messages sent to and received from a UDDI server.
The UDDI4J documentation gives a good and compact overview of UDDI4J.
Here are a list of simple UDDI4J code samples.
UDDI4J JavaDoc provides UDDI4J API reference.