Sort:  

Although I am not a big fan of Java programming I do know a little about RxJava and Akka Streams which in my opinion make for a great tool belt these days. I could recommend you head for Learning RxJava or RxJava Essentials.

My preference at the moment regarding reactive programming lies in using other technologies, mainly around using nodejs and redux-observable or using cycle.js

Thanks, I build for Java and would just want a clean way to handle concurrency, i find it a liitle bit hard to comprehend so i hardly use it in projects i do.