If you want to know what Xenon is, I suggest you take a look at the main Xenon repo
I dont like Xenon, and aparently neither does VMware because they've decided to stop supporting the project. There is one thing I do like about Xenon; its wrapper on CompletableFuture called DeferredResult. The two are VERY similar but there are a few tweaks that I prefer over the vanilla CompletableFuture.
When starting a new project, I dont want to incorportate Xenon, but it would be nice to pull in just DeferredResults. That is why I decided to (on my own time) fork Xenon and delete EVERYTHING except for DeferredResults.
To consume Xenon-dr, include this dependency in your maven repo:
<dependency>
<groupId>com.vmware.xenon</groupId>
<artifactId>xenon-dr</artifactId>
<version>1.7.0-SNAPSHOT</version>
</dependency>