java.util.concurrent Helpers for joining Futures using Tuples

[billoneil]

Possibly create a way to join and map CompletableFutures.

public static <T1, T2, T3> Tuple3<T1, T2, T3> joinAll(
        CompletableFuture<T1> f1,
        CompletableFuture<T2> f2,
        CompletableFuture<T3> f3) {
    // Do we even need this allOf since we join below anyway.
    CompletableFuture.allOf(f1, f2, f3).join();

    return Tuple.tuple(f1.join(), f2.join(), f3.join());
}

Could be combined like so.
return Futures.joinAll(emailFuture, tagFuture, rolesFuture).map(User::new);

Full example shown here https://gist.github.com/billoneil/f949def19560f379bec9aa640b19120c#file-gistfile1-java-L23

[lukaseder]

Thank you very much for your suggestion. That is an interesting approach. Should we decide to provide utilities for the JDK's concurrency APIs (see also #283), this multi-join-into-tuple approach definitely makes sense.

[billoneil]

@lukaseder any thoughts on this since we added the new CompletionStage? Ideally it would accept CompletionStages but they would need to be converted to CompletableFuture to call join() or CompletableFuture.allOf(

[lukaseder]

Thanks for pinging, @billoneil. I think this idea needs to ripe a bit, first. Improving this area seems to be scratching an itch that few people have, and at this stage, I'm very uncertain of what a good API would be. I currently don't want to rush adding this new API.

[billoneil]

No problem totally agree. Just wanted to see if you had any thoughts. I might make something similar internally and see if I like it.