Operator BO.forEachFuture

[akarnokd]

Issue #634

I tried to find a random place in BO but it is likely this or the other PRs will not merge one after another.

[cloudbees-pull-request-builder]

RxJava-pull-requests #578 SUCCESS
This pull request looks good

[benjchristensen]

In Rx.Net it had clean design with Task and async/await. In Java we don't. This (and other similar pull requests) don't make much sense and are greatly complicating the API.

In Java the Future/FutureTask/Callable/Runnable/CompletableFuture set of classes do not play well with the non-blocking/reactive style of Rx, nor is there good conformity across JVM languages (Scala, Groovy, Clojure with different concurrency models and libraries) or even Java libraries (such as Guava and Akka).

I think that all of these additions you are proposing related to java.util.concurrent interop should be pushed into a separate contrib module and not part of core. Perhaps rxjava-contrib/rxjava-java-future or something along those lines?

In short, the goal is to keep rxjava-core focused on the basics of Observable and non-blocking operators. Interop with the various different approaches to concurrency should be kept separate. In retrospect even the Async.java stuff should likely be moved out to this new contrib module.

[akarnokd]

Yes, a contrib module would be much cleaner.

[benjchristensen]

Great, I'm glad we agree. I'll setup the module for you.

[benjchristensen]

Merge these into #696 instead.