We have just released a release candidate for the Java agent: https://github.com/elastic/apm-agent-java/releases/tag/v1.0.0.RC1
This is your chance to give us feedback before the general availability (1.0.0 release) of the agent. It comes with lots of cool stuff like support for distributed tracing, an annotation based API for creating transactions and spans as well as support for the Elasticsearch Rest Client.
Note that the agent 1.0.0.RC1 only compatible with the upcoming APM Server version 6.5.0. At the time of writing, this version is not released yet.