what's the closest thing in java to `suspend fun getAThingThatMayTakeTime() : T`? `fun getAThing(): ...

# coroutines

[Marko Mitic]

what's the closest thing in java to suspend fun getAThingThatMayTakeTime() : T?
fun getAThing(): Future<T> ?

[jw]

More like CompletableFuture or ListenableFuture or RxJava's Single

[Dominaezzz]

fun getAThing(cont: Continuation<T>) 😛

[Marko Mitic]

Followup: is there any easy way to wrap suspend call into Future/ListenableFuture (on Android)

[Marko Mitic]

Ok, i see this https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-jdk8/kotlinx.coroutines.future/kotlinx.coroutines.-deferred/as-completable-future.html

[Marko Mitic]

is it safe to use on Android with limited java 8 api?

[Marko Mitic]

I'll assume it's not 😄

[Dominaezzz]

From java or from kotlin?

[Dominaezzz]

Are you trying to allow java call your kotlin suspend function?

[Dominaezzz]

If you want to explicitly support java, don't bother with suspension.

[Dominaezzz]

Just use GlobalScope.future.

[diesieben07]

Nothing wrong with using suspension in your kotlin code, that's what the adapters like future, etc. are for

[diesieben07]

You can write normal suspend functions and then adapter methods for calling from Java

[Dominaezzz]

Do you have any examples?

[diesieben07]

suspend fun doStuff() {

}

fun doStuffJava() = GlobalScope.future { doStuff() }

[diesieben07]

This way both Kotlin and Java can call it idiomatically

[Marko Mitic]

Yeah, I'm trying to let java call my suspend API (indirectly)

[diesieben07]

future (and other helpers) are the way to go then

[Marko Mitic]

I don't see GlobalScope.future, what dependency do I need for that?

[diesieben07]

For CompletableFuture: https://github.com/Kotlin/kotlinx.coroutines/tree/master/integration/kotlinx-coroutines-jdk8

[diesieben07]

There is also one for guava, giving a wrapper for ListenableFuture

[diesieben07]

https://github.com/Kotlin/kotlinx.coroutines/tree/master/integration

[Dominaezzz]

What about interfaces?

[diesieben07]

What about them?

[Marko Mitic]

I don't have full Java8 API on android, I don't think I can use kotlinx-coroutines-jdk8, I'll try implementing something myself

[diesieben07]

You do need some kind of future if you want to use it from Java

[diesieben07]

If you can't use Api level 24 (not quite sure how this works on Android) then you should use Guava

[Dominaezzz]

How do you provide an adapter without repeating yourself?

[diesieben07]

I don't think you can. You have to explicitly design for Java interop with coroutines

[Dominaezzz]

Guava comes with androidx. In some form.

[jw]

It does not

[jw]

There is a ListenableFuture artifact which provides a SettableFuture that you can use

[jw]

Definitely do not expose just a Future. It is an entirely useless type.

[Marko Mitic]

blocking call it is, thank you everybody