Integration with JDK8 CompletableFuture
(Android API level 24).
Coroutine builders:
Name | Result | Scope | Description |
---|---|---|---|
future | CompletableFuture | CoroutineScope | Returns a single value with the future result |
Extension functions:
Name | Description |
---|---|
CompletionStage.await | Awaits for completion of the completion stage (non-cancellable) |
CompletableFuture.await | Awaits for completion of the future (cancellable) |
Deferred.asCompletableFuture | Converts a deferred value to the future |
Given the following functions defined in some Java API:
public CompletableFuture<Image> loadImageAsync(String name); // starts async image loading public Image combineImages(Image image1, Image image2); // synchronously combines two images using some algorithm
We can consume this API from Kotlin coroutine to load two images and combine then asynchronously. The resulting function returns CompletableFuture<Image>
for ease of use back from Java.
fun combineImagesAsync(name1: String, name2: String): CompletableFuture<Image> = future { val future1 = loadImageAsync(name1) // start loading first image val future2 = loadImageAsync(name2) // start loading second image combineImages(future1.await(), future2.await()) // wait for both, combine, and return result }
Note, that this module should be used only for integration with existing Java APIs based on CompletableFuture
. Writing pure-Kotlin code that uses CompletableFuture
is highly not recommended, since the resulting APIs based on the futures are quite error-prone. See the discussion on Asynchronous Programming Styles for details on general problems pertaining to any future-based API and keep in mind that CompletableFuture
exposes a blocking method get that makes it especially bad choice for coroutine-based Kotlin code.
Integration with JDK8 CompletableFuture
(Android API level 24).