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/OpenJDK 8

Class CompletableFuture<T>

All Implemented Interfaces:
CompletionStage<T>, Future<T>
public class CompletableFuture<T>
extends Object
implements Future<T>, CompletionStage<T>

A Future that may be explicitly completed (setting its value and status), and may be used as a CompletionStage, supporting dependent functions and actions that trigger upon its completion.

When two or more threads attempt to complete, completeExceptionally, or cancel a CompletableFuture, only one of them succeeds.

In addition to these and related methods for directly manipulating status and results, CompletableFuture implements interface CompletionStage with the following policies:

  • Actions supplied for dependent completions of non-async methods may be performed by the thread that completes the current CompletableFuture, or by any other caller of a completion method.
  • All async methods without an explicit Executor argument are performed using the ForkJoinPool.commonPool() (unless it does not support a parallelism level of at least two, in which case, a new Thread is created to run each task). To simplify monitoring, debugging, and tracking, all generated asynchronous tasks are instances of the marker interface CompletableFuture.AsynchronousCompletionTask.
  • All CompletionStage methods are implemented independently of other public methods, so the behavior of one method is not impacted by overrides of others in subclasses.

CompletableFuture also implements Future with the following policies:

  • Since (unlike FutureTask) this class has no direct control over the computation that causes it to be completed, cancellation is treated as just another form of exceptional completion. Method cancel has the same effect as completeExceptionally(new CancellationException()). Method isCompletedExceptionally() can be used to determine if a CompletableFuture completed in any exceptional fashion.
  • In case of exceptional completion with a CompletionException, methods get() and get(long, TimeUnit) throw an ExecutionException with the same cause as held in the corresponding CompletionException. To simplify usage in most contexts, this class also defines methods join() and getNow(T) that instead throw the CompletionException directly in these cases.
Since:
1.8

Nested Classes

Nested Classes
Modifier and Type Class and Description
static interface  CompletableFuture.AsynchronousCompletionTask

A marker interface identifying asynchronous tasks produced by async methods.

Constructors

CompletableFuture

public CompletableFuture()

Creates a new incomplete CompletableFuture.

Methods

supplyAsync

public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier)

Returns a new CompletableFuture that is asynchronously completed by a task running in the ForkJoinPool.commonPool() with the value obtained by calling the given Supplier.

Type Parameters:
U - the function's return type
Parameters:
supplier - a function returning the value to be used to complete the returned CompletableFuture
Returns:
the new CompletableFuture

supplyAsync

public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier,
                                                   Executor executor)

Returns a new CompletableFuture that is asynchronously completed by a task running in the given executor with the value obtained by calling the given Supplier.

Type Parameters:
U - the function's return type
Parameters:
supplier - a function returning the value to be used to complete the returned CompletableFuture
executor - the executor to use for asynchronous execution
Returns:
the new CompletableFuture

runAsync

public static CompletableFuture<Void> runAsync(Runnable runnable)

Returns a new CompletableFuture that is asynchronously completed by a task running in the ForkJoinPool.commonPool() after it runs the given action.

Parameters:
runnable - the action to run before completing the returned CompletableFuture
Returns:
the new CompletableFuture

runAsync

public static CompletableFuture<Void> runAsync(Runnable runnable,
                                               Executor executor)

Returns a new CompletableFuture that is asynchronously completed by a task running in the given executor after it runs the given action.

Parameters:
runnable - the action to run before completing the returned CompletableFuture
executor - the executor to use for asynchronous execution
Returns:
the new CompletableFuture

completedFuture

public static <U> CompletableFuture<U> completedFuture(U value)

Returns a new CompletableFuture that is already completed with the given value.

Type Parameters:
U - the type of the value
Parameters:
value - the value
Returns:
the completed CompletableFuture

isDone

public boolean isDone()

Returns true if completed in any fashion: normally, exceptionally, or via cancellation.

Specified by:
isDone in interface Future<T>
Returns:
true if completed

get

public T get()
      throws InterruptedException,
             ExecutionException

Waits if necessary for this future to complete, and then returns its result.

Specified by:
get in interface Future<T>
Returns:
the result value
Throws:
CancellationException - if this future was cancelled
ExecutionException - if this future completed exceptionally
InterruptedException - if the current thread was interrupted while waiting

get

public T get(long timeout,
             TimeUnit unit)
      throws InterruptedException,
             ExecutionException,
             TimeoutException

Waits if necessary for at most the given time for this future to complete, and then returns its result, if available.

Specified by:
get in interface Future<T>
Parameters:
timeout - the maximum time to wait
unit - the time unit of the timeout argument
Returns:
the result value
Throws:
CancellationException - if this future was cancelled
ExecutionException - if this future completed exceptionally
InterruptedException - if the current thread was interrupted while waiting
TimeoutException - if the wait timed out

join

public T join()

Returns the result value when complete, or throws an (unchecked) exception if completed exceptionally. To better conform with the use of common functional forms, if a computation involved in the completion of this CompletableFuture threw an exception, this method throws an (unchecked) CompletionException with the underlying exception as its cause.

Returns:
the result value
Throws:
CancellationException - if the computation was cancelled
CompletionException - if this future completed exceptionally or a completion computation threw an exception

getNow

public T getNow(T valueIfAbsent)

Returns the result value (or throws any encountered exception) if completed, else returns the given valueIfAbsent.

Parameters:
valueIfAbsent - the value to return if not completed
Returns:
the result value, if completed, else the given valueIfAbsent
Throws:
CancellationException - if the computation was cancelled
CompletionException - if this future completed exceptionally or a completion computation threw an exception

complete

public boolean complete(T value)

If not already completed, sets the value returned by get() and related methods to the given value.

Parameters:
value - the result value
Returns:
true if this invocation caused this CompletableFuture to transition to a completed state, else false

completeExceptionally

public boolean completeExceptionally(Throwable ex)

If not already completed, causes invocations of get() and related methods to throw the given exception.

Parameters:
ex - the exception
Returns:
true if this invocation caused this CompletableFuture to transition to a completed state, else false

thenApply

public <U> CompletableFuture<U> thenApply(Function<? super T,? extends U> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed with this stage's result as the argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenApply in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
fn - the function to use to compute the value of the returned CompletionStage
Returns:
the new CompletionStage

thenApplyAsync

public <U> CompletableFuture<U> thenApplyAsync(Function<? super T,? extends U> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed using this stage's default asynchronous execution facility, with this stage's result as the argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenApplyAsync in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
fn - the function to use to compute the value of the returned CompletionStage
Returns:
the new CompletionStage

thenApplyAsync

public <U> CompletableFuture<U> thenApplyAsync(Function<? super T,? extends U> fn,
                                               Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed using the supplied Executor, with this stage's result as the argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenApplyAsync in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
fn - the function to use to compute the value of the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

thenAccept

public CompletableFuture<Void> thenAccept(Consumer<? super T> action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed with this stage's result as the argument to the supplied action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenAccept in interface CompletionStage<T>
Parameters:
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

thenAcceptAsync

public CompletableFuture<Void> thenAcceptAsync(Consumer<? super T> action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed using this stage's default asynchronous execution facility, with this stage's result as the argument to the supplied action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenAcceptAsync in interface CompletionStage<T>
Parameters:
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

thenAcceptAsync

public CompletableFuture<Void> thenAcceptAsync(Consumer<? super T> action,
                                               Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed using the supplied Executor, with this stage's result as the argument to the supplied action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenAcceptAsync in interface CompletionStage<T>
Parameters:
action - the action to perform before completing the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

thenRun

public CompletableFuture<Void> thenRun(Runnable action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, executes the given action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenRun in interface CompletionStage<T>
Parameters:
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

thenRunAsync

public CompletableFuture<Void> thenRunAsync(Runnable action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, executes the given action using this stage's default asynchronous execution facility. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenRunAsync in interface CompletionStage<T>
Parameters:
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

thenRunAsync

public CompletableFuture<Void> thenRunAsync(Runnable action,
                                            Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, executes the given action using the supplied Executor. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenRunAsync in interface CompletionStage<T>
Parameters:
action - the action to perform before completing the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

thenCombine

public <U,V> CompletableFuture<V> thenCombine(CompletionStage<? extends U> other,
                                              BiFunction<? super T,? super U,? extends V> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage both complete normally, is executed with the two results as arguments to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenCombine in interface CompletionStage<T>
Type Parameters:
U - the type of the other CompletionStage's result
V - the function's return type
Parameters:
other - the other CompletionStage
fn - the function to use to compute the value of the returned CompletionStage
Returns:
the new CompletionStage

thenCombineAsync

public <U,V> CompletableFuture<V> thenCombineAsync(CompletionStage<? extends U> other,
                                                   BiFunction<? super T,? super U,? extends V> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage complete normally, is executed using this stage's default asynchronous execution facility, with the two results as arguments to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenCombineAsync in interface CompletionStage<T>
Type Parameters:
U - the type of the other CompletionStage's result
V - the function's return type
Parameters:
other - the other CompletionStage
fn - the function to use to compute the value of the returned CompletionStage
Returns:
the new CompletionStage

thenCombineAsync

public <U,V> CompletableFuture<V> thenCombineAsync(CompletionStage<? extends U> other,
                                                   BiFunction<? super T,? super U,? extends V> fn,
                                                   Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage complete normally, is executed using the supplied executor, with the two results as arguments to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenCombineAsync in interface CompletionStage<T>
Type Parameters:
U - the type of the other CompletionStage's result
V - the function's return type
Parameters:
other - the other CompletionStage
fn - the function to use to compute the value of the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

thenAcceptBoth

public <U> CompletableFuture<Void> thenAcceptBoth(CompletionStage<? extends U> other,
                                                  BiConsumer<? super T,? super U> action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage both complete normally, is executed with the two results as arguments to the supplied action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenAcceptBoth in interface CompletionStage<T>
Type Parameters:
U - the type of the other CompletionStage's result
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

thenAcceptBothAsync

public <U> CompletableFuture<Void> thenAcceptBothAsync(CompletionStage<? extends U> other,
                                                       BiConsumer<? super T,? super U> action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage complete normally, is executed using this stage's default asynchronous execution facility, with the two results as arguments to the supplied action.

Specified by:
thenAcceptBothAsync in interface CompletionStage<T>
Type Parameters:
U - the type of the other CompletionStage's result
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

thenAcceptBothAsync

public <U> CompletableFuture<Void> thenAcceptBothAsync(CompletionStage<? extends U> other,
                                                       BiConsumer<? super T,? super U> action,
                                                       Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage complete normally, is executed using the supplied executor, with the two results as arguments to the supplied function.

Specified by:
thenAcceptBothAsync in interface CompletionStage<T>
Type Parameters:
U - the type of the other CompletionStage's result
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

runAfterBoth

public CompletableFuture<Void> runAfterBoth(CompletionStage<?> other,
                                            Runnable action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage both complete normally, executes the given action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
runAfterBoth in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

runAfterBothAsync

public CompletableFuture<Void> runAfterBothAsync(CompletionStage<?> other,
                                                 Runnable action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage complete normally, executes the given action using this stage's default asynchronous execution facility. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
runAfterBothAsync in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

runAfterBothAsync

public CompletableFuture<Void> runAfterBothAsync(CompletionStage<?> other,
                                                 Runnable action,
                                                 Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this and the other given stage complete normally, executes the given action using the supplied executor. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
runAfterBothAsync in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

applyToEither

public <U> CompletableFuture<U> applyToEither(CompletionStage<? extends T> other,
                                              Function<? super T,U> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, is executed with the corresponding result as argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
applyToEither in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
other - the other CompletionStage
fn - the function to use to compute the value of the returned CompletionStage
Returns:
the new CompletionStage

applyToEitherAsync

public <U> CompletableFuture<U> applyToEitherAsync(CompletionStage<? extends T> other,
                                                   Function<? super T,U> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, is executed using this stage's default asynchronous execution facility, with the corresponding result as argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
applyToEitherAsync in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
other - the other CompletionStage
fn - the function to use to compute the value of the returned CompletionStage
Returns:
the new CompletionStage

applyToEitherAsync

public <U> CompletableFuture<U> applyToEitherAsync(CompletionStage<? extends T> other,
                                                   Function<? super T,U> fn,
                                                   Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, is executed using the supplied executor, with the corresponding result as argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
applyToEitherAsync in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
other - the other CompletionStage
fn - the function to use to compute the value of the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

acceptEither

public CompletableFuture<Void> acceptEither(CompletionStage<? extends T> other,
                                            Consumer<? super T> action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, is executed with the corresponding result as argument to the supplied action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
acceptEither in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

acceptEitherAsync

public CompletableFuture<Void> acceptEitherAsync(CompletionStage<? extends T> other,
                                                 Consumer<? super T> action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, is executed using this stage's default asynchronous execution facility, with the corresponding result as argument to the supplied action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
acceptEitherAsync in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

acceptEitherAsync

public CompletableFuture<Void> acceptEitherAsync(CompletionStage<? extends T> other,
                                                 Consumer<? super T> action,
                                                 Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, is executed using the supplied executor, with the corresponding result as argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
acceptEitherAsync in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

runAfterEither

public CompletableFuture<Void> runAfterEither(CompletionStage<?> other,
                                              Runnable action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, executes the given action. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
runAfterEither in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

runAfterEitherAsync

public CompletableFuture<Void> runAfterEitherAsync(CompletionStage<?> other,
                                                   Runnable action)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, executes the given action using this stage's default asynchronous execution facility. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
runAfterEitherAsync in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
Returns:
the new CompletionStage

runAfterEitherAsync

public CompletableFuture<Void> runAfterEitherAsync(CompletionStage<?> other,
                                                   Runnable action,
                                                   Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when either this or the other given stage complete normally, executes the given action using the supplied executor. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
runAfterEitherAsync in interface CompletionStage<T>
Parameters:
other - the other CompletionStage
action - the action to perform before completing the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

thenCompose

public <U> CompletableFuture<U> thenCompose(Function<? super T,? extends CompletionStage<U>> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed with this stage as the argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenCompose in interface CompletionStage<T>
Type Parameters:
U - the type of the returned CompletionStage's result
Parameters:
fn - the function returning a new CompletionStage
Returns:
the CompletionStage

thenComposeAsync

public <U> CompletableFuture<U> thenComposeAsync(Function<? super T,? extends CompletionStage<U>> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed using this stage's default asynchronous execution facility, with this stage as the argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenComposeAsync in interface CompletionStage<T>
Type Parameters:
U - the type of the returned CompletionStage's result
Parameters:
fn - the function returning a new CompletionStage
Returns:
the CompletionStage

thenComposeAsync

public <U> CompletableFuture<U> thenComposeAsync(Function<? super T,? extends CompletionStage<U>> fn,
                                                 Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes normally, is executed using the supplied Executor, with this stage's result as the argument to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Specified by:
thenComposeAsync in interface CompletionStage<T>
Type Parameters:
U - the type of the returned CompletionStage's result
Parameters:
fn - the function returning a new CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the CompletionStage

whenComplete

public CompletableFuture<T> whenComplete(BiConsumer<? super T,? super Throwable> action)

Description copied from interface: CompletionStage

Returns a new CompletionStage with the same result or exception as this stage, that executes the given action when this stage completes.

When this stage is complete, the given action is invoked with the result (or null if none) and the exception (or null if none) of this stage as arguments. The returned stage is completed when the action returns. If the supplied action itself encounters an exception, then the returned stage exceptionally completes with this exception unless this stage also completed exceptionally.

Specified by:
whenComplete in interface CompletionStage<T>
Parameters:
action - the action to perform
Returns:
the new CompletionStage

whenCompleteAsync

public CompletableFuture<T> whenCompleteAsync(BiConsumer<? super T,? super Throwable> action)

Description copied from interface: CompletionStage

Returns a new CompletionStage with the same result or exception as this stage, that executes the given action using this stage's default asynchronous execution facility when this stage completes.

When this stage is complete, the given action is invoked with the result (or null if none) and the exception (or null if none) of this stage as arguments. The returned stage is completed when the action returns. If the supplied action itself encounters an exception, then the returned stage exceptionally completes with this exception unless this stage also completed exceptionally.

Specified by:
whenCompleteAsync in interface CompletionStage<T>
Parameters:
action - the action to perform
Returns:
the new CompletionStage

whenCompleteAsync

public CompletableFuture<T> whenCompleteAsync(BiConsumer<? super T,? super Throwable> action,
                                              Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage with the same result or exception as this stage, that executes the given action using the supplied Executor when this stage completes.

When this stage is complete, the given action is invoked with the result (or null if none) and the exception (or null if none) of this stage as arguments. The returned stage is completed when the action returns. If the supplied action itself encounters an exception, then the returned stage exceptionally completes with this exception unless this stage also completed exceptionally.

Specified by:
whenCompleteAsync in interface CompletionStage<T>
Parameters:
action - the action to perform
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

handle

public <U> CompletableFuture<U> handle(BiFunction<? super T,Throwable,? extends U> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes either normally or exceptionally, is executed with this stage's result and exception as arguments to the supplied function.

When this stage is complete, the given function is invoked with the result (or null if none) and the exception (or null if none) of this stage as arguments, and the function's result is used to complete the returned stage.

Specified by:
handle in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
fn - the function to use to compute the value of the returned CompletionStage
Returns:
the new CompletionStage

handleAsync

public <U> CompletableFuture<U> handleAsync(BiFunction<? super T,Throwable,? extends U> fn)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes either normally or exceptionally, is executed using this stage's default asynchronous execution facility, with this stage's result and exception as arguments to the supplied function.

When this stage is complete, the given function is invoked with the result (or null if none) and the exception (or null if none) of this stage as arguments, and the function's result is used to complete the returned stage.

Specified by:
handleAsync in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
fn - the function to use to compute the value of the returned CompletionStage
Returns:
the new CompletionStage

handleAsync

public <U> CompletableFuture<U> handleAsync(BiFunction<? super T,Throwable,? extends U> fn,
                                            Executor executor)

Description copied from interface: CompletionStage

Returns a new CompletionStage that, when this stage completes either normally or exceptionally, is executed using the supplied executor, with this stage's result and exception as arguments to the supplied function.

When this stage is complete, the given function is invoked with the result (or null if none) and the exception (or null if none) of this stage as arguments, and the function's result is used to complete the returned stage.

Specified by:
handleAsync in interface CompletionStage<T>
Type Parameters:
U - the function's return type
Parameters:
fn - the function to use to compute the value of the returned CompletionStage
executor - the executor to use for asynchronous execution
Returns:
the new CompletionStage

toCompletableFuture

public CompletableFuture<T> toCompletableFuture()

Returns this CompletableFuture.

Specified by:
toCompletableFuture in interface CompletionStage<T>
Returns:
this CompletableFuture

exceptionally

public CompletableFuture<T> exceptionally(Function<Throwable,? extends T> fn)

Returns a new CompletableFuture that is completed when this CompletableFuture completes, with the result of the given function of the exception triggering this CompletableFuture's completion when it completes exceptionally; otherwise, if this CompletableFuture completes normally, then the returned CompletableFuture also completes normally with the same value. Note: More flexible versions of this functionality are available using methods whenComplete and handle.

Specified by:
exceptionally in interface CompletionStage<T>
Parameters:
fn - the function to use to compute the value of the returned CompletableFuture if this CompletableFuture completed exceptionally
Returns:
the new CompletableFuture

allOf

public static CompletableFuture<Void> allOf(CompletableFuture<?>... cfs)

Returns a new CompletableFuture that is completed when all of the given CompletableFutures complete. If any of the given CompletableFutures complete exceptionally, then the returned CompletableFuture also does so, with a CompletionException holding this exception as its cause. Otherwise, the results, if any, of the given CompletableFutures are not reflected in the returned CompletableFuture, but may be obtained by inspecting them individually. If no CompletableFutures are provided, returns a CompletableFuture completed with the value null.

Among the applications of this method is to await completion of a set of independent CompletableFutures before continuing a program, as in: CompletableFuture.allOf(c1, c2, c3).join();.

Parameters:
cfs - the CompletableFutures
Returns:
a new CompletableFuture that is completed when all of the given CompletableFutures complete
Throws:
NullPointerException - if the array or any of its elements are null

anyOf

public static CompletableFuture<Object> anyOf(CompletableFuture<?>... cfs)

Returns a new CompletableFuture that is completed when any of the given CompletableFutures complete, with the same result. Otherwise, if it completed exceptionally, the returned CompletableFuture also does so, with a CompletionException holding this exception as its cause. If no CompletableFutures are provided, returns an incomplete CompletableFuture.

Parameters:
cfs - the CompletableFutures
Returns:
a new CompletableFuture that is completed with the result or exception of any of the given CompletableFutures when one completes
Throws:
NullPointerException - if the array or any of its elements are null

cancel

public boolean cancel(boolean mayInterruptIfRunning)

If not already completed, completes this CompletableFuture with a CancellationException. Dependent CompletableFutures that have not already completed will also complete exceptionally, with a CompletionException caused by this CancellationException.

Specified by:
cancel in interface Future<T>
Parameters:
mayInterruptIfRunning - this value has no effect in this implementation because interrupts are not used to control processing.
Returns:
true if this task is now cancelled

isCancelled

public boolean isCancelled()

Returns true if this CompletableFuture was cancelled before it completed normally.

Specified by:
isCancelled in interface Future<T>
Returns:
true if this CompletableFuture was cancelled before it completed normally

isCompletedExceptionally

public boolean isCompletedExceptionally()

Returns true if this CompletableFuture completed exceptionally, in any way. Possible causes include cancellation, explicit invocation of completeExceptionally, and abrupt termination of a CompletionStage action.

Returns:
true if this CompletableFuture completed exceptionally

obtrudeValue

public void obtrudeValue(T value)

Forcibly sets or resets the value subsequently returned by method get() and related methods, whether or not already completed. This method is designed for use only in error recovery actions, and even in such situations may result in ongoing dependent completions using established versus overwritten outcomes.

Parameters:
value - the completion value

obtrudeException

public void obtrudeException(Throwable ex)

Forcibly causes subsequent invocations of method get() and related methods to throw the given exception, whether or not already completed. This method is designed for use only in error recovery actions, and even in such situations may result in ongoing dependent completions using established versus overwritten outcomes.

Parameters:
ex - the exception
Throws:
NullPointerException - if the exception is null

getNumberOfDependents

public int getNumberOfDependents()

Returns the estimated number of CompletableFutures whose completions are awaiting completion of this CompletableFuture. This method is designed for use in monitoring system state, not for synchronization control.

Returns:
the number of dependent CompletableFutures

toString

public String toString()

Returns a string identifying this CompletableFuture, as well as its completion state. The state, in brackets, contains the String "Completed Normally" or the String "Completed Exceptionally", or the String "Not completed" followed by the number of CompletableFutures dependent upon its completion, if any.

Overrides:
toString in class Object
Returns:
a string identifying this CompletableFuture, as well as its state

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