scala.compat.java8

Class FutureConverters$

java.lang.Object

scala.compat.java8.FutureConverters$

public class FutureConverters$
extends java.lang.Object

This class contains static methods which convert between Java CompletionStage and Scala Future. This is useful when mediating between Scala and Java libraries with asynchronous APIs.

Note that the bridge is implemented at the read-only side of asynchronous handles, namely scala.concurrent.Future instead of scala.concurrent.Promise and CompletionStage instead of CompletableFuture. This is intentional, as the semantics of bridging the write-handles would be prone to race conditions; if both ends (CompletableFuture and Promise) are completed independently at the same time, they may contain different values afterwards. For this reason, toCompletableFuture() is not supported on the created CompletionStages.

Example usage:

 import java.util.concurrent.CompletionStage;
 import scala.concurrent.Future;
 import static scala.concurrent.java8.FutureConverter.*;

 final CompletionStage<String> cs = ... // from an async Java API
 final Future<String> f = toScala(cs);
 ...
 final Future<Integer> f2 = ... // from an async Scala API
 final CompletionStage<Integer> cs2 = toJava(f2);
 

Field Summary

Fields

Modifier and Type	Field and Description
static FutureConverters$	MODULE$ Static reference to the singleton instance of this Scala object.

Constructor Summary

Constructors

Constructor and Description
FutureConverters$()

Method Summary

Modifier and Type	Method and Description
<T> FutureConverters.CompletionStageOps<T>	CompletionStageOps(java.util.concurrent.CompletionStage<T> cs)
<T> scala.concurrent.Promise<T>	failedPromise(java.lang.Throwable ex) Construct an already fulfilled scala.concurrent.Promise which holds the given failure.
scala.concurrent.ExecutionContextExecutor	fromExecutor(java.util.concurrent.Executor e) Creates an ExecutionContext from a given Executor, using the default reporter for uncaught exceptions which will just call .printStackTrace().
scala.concurrent.ExecutionContextExecutor	fromExecutor(java.util.concurrent.Executor e, java.util.function.Consumer<java.lang.Throwable> reporter) Creates an ExecutionContext from a given Executor, using the given Consumer for reporting errors.
scala.concurrent.ExecutionContextExecutorService	fromExecutorService(java.util.concurrent.ExecutorService e) Creates an ExecutionContext from a given ExecutorService, using the default reporter for uncaught exceptions which will just call .printStackTrace().
scala.concurrent.ExecutionContextExecutorService	fromExecutorService(java.util.concurrent.ExecutorService e, java.util.function.Consumer<java.lang.Throwable> reporter) Creates an ExecutionContext from a given ExecutorService, using the given Consumer for reporting errors.
<T> FutureConverters.FutureOps<T>	FutureOps(scala.concurrent.Future<T> f)
scala.concurrent.ExecutionContext	globalExecutionContext() Return the global ExecutionContext for Scala Futures.
<T> scala.concurrent.Promise<T>	keptPromise(T v) Construct an already fulfilled scala.concurrent.Promise which holds the given value.
<T> scala.concurrent.Promise<T>	promise() Construct an empty scala.concurrent.Promise.
<T> java.util.concurrent.CompletionStage<T>	toJava(scala.concurrent.Future<T> f) Returns a CompletionStage that will be completed with the same value or exception as the given Scala Future when that completes.
<T> scala.concurrent.Future<T>	toScala(java.util.concurrent.CompletionStage<T> cs) Returns a Scala Future that will be completed with the same value or exception as the given CompletionStage when that completes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MODULE$

public static final FutureConverters$ MODULE$

Static reference to the singleton instance of this Scala object.

Constructor Detail

FutureConverters$

public FutureConverters$()

Method Detail

toJava

public <T> java.util.concurrent.CompletionStage<T> toJava(scala.concurrent.Future<T> f)

Returns a CompletionStage that will be completed with the same value or exception as the given Scala Future when that completes. Since the Future is a read-only representation, this CompletionStage does not support the toCompletableFuture method. The semantics of Scala Future demand that all callbacks are invoked asynchronously by default, therefore the returned CompletionStage routes all calls to synchronous transformations to their asynchronous counterparts, i.e. thenRun will internally call thenRunAsync.

Parameters:

f - The Scala Future which may eventually supply the completion for the returned CompletionStage

Returns:

a CompletionStage that runs all callbacks asynchronously and does not support the CompletableFuture interface

toScala

public <T> scala.concurrent.Future<T> toScala(java.util.concurrent.CompletionStage<T> cs)

Returns a Scala Future that will be completed with the same value or exception as the given CompletionStage when that completes. Transformations of the returned Future are executed asynchronously as specified by the ExecutionContext that is given to the combinator methods.

Parameters:

cs - The CompletionStage which may eventually supply the completion for the returned Scala Future

Returns:

a Scala Future that represents the CompletionStage's completion

fromExecutorService

public scala.concurrent.ExecutionContextExecutorService fromExecutorService(java.util.concurrent.ExecutorService e,
                                                                            java.util.function.Consumer<java.lang.Throwable> reporter)

Creates an ExecutionContext from a given ExecutorService, using the given Consumer for reporting errors. The latter can be created as in the following example:

 final ExecutionContext ec = Converter.fromExecutorService(es, thr -> thr.printStackTrace());
 

Parameters:

e - an ExecutorService

reporter - a Consumer for reporting errors during execution

Returns:

an ExecutionContext backed by the given ExecutorService

fromExecutorService

public scala.concurrent.ExecutionContextExecutorService fromExecutorService(java.util.concurrent.ExecutorService e)

Creates an ExecutionContext from a given ExecutorService, using the default reporter for uncaught exceptions which will just call .printStackTrace().

Parameters:

e - an ExecutorService

Returns:

an ExecutionContext backed by the given ExecutorService

fromExecutor

public scala.concurrent.ExecutionContextExecutor fromExecutor(java.util.concurrent.Executor e,
                                                              java.util.function.Consumer<java.lang.Throwable> reporter)

Creates an ExecutionContext from a given Executor, using the given Consumer for reporting errors. The latter can be created as in the following example:

 final ExecutionContext ec = Converter.fromExecutor(es, thr -> thr.printStackTrace());
 

Parameters:

e - an Executor

reporter - a Consumer for reporting errors during execution

Returns:

an ExecutionContext backed by the given Executor

fromExecutor

public scala.concurrent.ExecutionContextExecutor fromExecutor(java.util.concurrent.Executor e)

Creates an ExecutionContext from a given Executor, using the default reporter for uncaught exceptions which will just call .printStackTrace().

Parameters:

e - an Executor

Returns:

an ExecutionContext backed by the given Executor

globalExecutionContext

public scala.concurrent.ExecutionContext globalExecutionContext()

Return the global ExecutionContext for Scala Futures.

Returns:

the ExecutionContext

promise

public <T> scala.concurrent.Promise<T> promise()

Construct an empty scala.concurrent.Promise.

Returns:

a Promise which is not yet completed

keptPromise

public <T> scala.concurrent.Promise<T> keptPromise(T v)

Construct an already fulfilled scala.concurrent.Promise which holds the given value.

Parameters:

v - (undocumented)

Returns:

the fulfilled Promise

failedPromise

public <T> scala.concurrent.Promise<T> failedPromise(java.lang.Throwable ex)

Construct an already fulfilled scala.concurrent.Promise which holds the given failure.

Parameters:

ex - (undocumented)

Returns:

the fulfilled Promise

FutureOps

public <T> FutureConverters.FutureOps<T> FutureOps(scala.concurrent.Future<T> f)

CompletionStageOps

public <T> FutureConverters.CompletionStageOps<T> CompletionStageOps(java.util.concurrent.CompletionStage<T> cs)