RxJava is also closely related to the reactive streams initiative and considers it self as a simple implementation of the reactive streams API (e.g. compared to the Akka streams implementation). The main difference is, that the reactive streams are designed to be able to handle back pressure, but if you have a look at the reactive streams page, you will get the idea. They describe their goals pretty well and the streams are also closely related to the reactive manifesto.
The Java 8 streams are pretty much the implementation of an unbounded collection, pretty similar to the Scala Stream or the Clojure lazy seqClojure lazy seq.