public interface CompletionStage<T>
A stage of a possibly asynchronous computation, that performs an action or computes a value when another CompletionStage completes. A stage completes upon termination of its computation, but this may in turn trigger other dependent stages. The functionality defined in this interface takes only a few basic forms, which expand out to a larger set of methods to capture a range of usage styles:
stage.thenApply(x -> square(x)).thenAccept(x ->
System.out.print(x)).thenRun(() -> System.out.println()). An additional form (compose) applies functions of stages themselves, rather than their results. Executor). The execution properties of default and async modes are specified by CompletionStage implementations, not this interface. Methods with explicit Executor arguments may have arbitrary execution properties, and might not even support concurrent execution, but are arranged for processing in a way that accommodates asynchrony. whenComplete allows injection of an action regardless of outcome, otherwise preserving the outcome in its completion. Method handle additionally allows the stage to compute a replacement result that may enable further processing by other dependent stages. In all other cases, if a stage's computation terminates abruptly with an (unchecked) exception or error, then all dependent stages requiring its completion complete exceptionally as well, with a CompletionException holding the exception as its cause. If a stage is dependent on both of two stages, and both complete exceptionally, then the CompletionException may correspond to either one of these exceptions. If a stage is dependent on either of two others, and only one of them completes exceptionally, no guarantees are made about whether the dependent stage completes normally or exceptionally. In the case of method whenComplete, when the supplied action itself encounters an exception, then the stage exceptionally completes with this exception if not already completed exceptionally.All methods adhere to the above triggering, execution, and exceptional completion specifications (which are not repeated in individual method specifications). Additionally, while arguments used to pass a completion result (that is, for parameters of type T) for methods accepting them may be null, passing a null value for any other parameter will result in a NullPointerException being thrown.
This interface does not define methods for initially creating, forcibly completing normally or exceptionally, probing completion status or results, or awaiting completion of a stage. Implementations of CompletionStage may provide means of achieving such effects, as appropriate. Method toCompletableFuture() enables interoperability among different implementations of this interface by providing a common conversion type.
<U> CompletionStage<U> thenApply(Function<? super T,? extends U> fn)
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.
U - the function's return typefn - the function to use to compute the value of the returned CompletionStage<U> CompletionStage<U> thenApplyAsync(Function<? super T,? extends U> fn)
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.
U - the function's return typefn - the function to use to compute the value of the returned CompletionStage<U> CompletionStage<U> thenApplyAsync(Function<? super T,? extends U> fn,
Executor executor) 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.
U - the function's return typefn - the function to use to compute the value of the returned CompletionStageexecutor - the executor to use for asynchronous executionCompletionStage<Void> thenAccept(Consumer<? super T> action)
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.
action - the action to perform before completing the returned CompletionStageCompletionStage<Void> thenAcceptAsync(Consumer<? super T> action)
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.
action - the action to perform before completing the returned CompletionStageCompletionStage<Void> thenAcceptAsync(Consumer<? super T> action,
Executor executor) 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.
action - the action to perform before completing the returned CompletionStageexecutor - the executor to use for asynchronous executionCompletionStage<Void> thenRun(Runnable action)
Returns a new CompletionStage that, when this stage completes normally, executes the given action. See the CompletionStage documentation for rules covering exceptional completion.
action - the action to perform before completing the returned CompletionStageCompletionStage<Void> thenRunAsync(Runnable action)
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.
action - the action to perform before completing the returned CompletionStageCompletionStage<Void> thenRunAsync(Runnable action,
Executor executor) 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.
action - the action to perform before completing the returned CompletionStageexecutor - the executor to use for asynchronous execution<U,V> CompletionStage<V> thenCombine(CompletionStage<? extends U> other,
BiFunction<? super T,? super U,? extends V> fn) 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.
U - the type of the other CompletionStage's resultV - the function's return typeother - the other CompletionStagefn - the function to use to compute the value of the returned CompletionStage<U,V> CompletionStage<V> thenCombineAsync(CompletionStage<? extends U> other,
BiFunction<? super T,? super U,? extends V> fn) 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.
U - the type of the other CompletionStage's resultV - the function's return typeother - the other CompletionStagefn - the function to use to compute the value of the returned CompletionStage<U,V> CompletionStage<V> thenCombineAsync(CompletionStage<? extends U> other,
BiFunction<? super T,? super U,? extends V> fn,
Executor executor) 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.
U - the type of the other CompletionStage's resultV - the function's return typeother - the other CompletionStagefn - the function to use to compute the value of the returned CompletionStageexecutor - the executor to use for asynchronous execution<U> CompletionStage<Void> thenAcceptBoth(CompletionStage<? extends U> other,
BiConsumer<? super T,? super U> action) 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.
U - the type of the other CompletionStage's resultother - the other CompletionStageaction - the action to perform before completing the returned CompletionStage<U> CompletionStage<Void> thenAcceptBothAsync(CompletionStage<? extends U> other,
BiConsumer<? super T,? super U> action) 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.
U - the type of the other CompletionStage's resultother - the other CompletionStageaction - the action to perform before completing the returned CompletionStage<U> CompletionStage<Void> thenAcceptBothAsync(CompletionStage<? extends U> other,
BiConsumer<? super T,? super U> action,
Executor executor) 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.
U - the type of the other CompletionStage's resultother - the other CompletionStageaction - the action to perform before completing the returned CompletionStageexecutor - the executor to use for asynchronous executionCompletionStage<Void> runAfterBoth(CompletionStage<?> other,
Runnable action) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageCompletionStage<Void> runAfterBothAsync(CompletionStage<?> other,
Runnable action) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageCompletionStage<Void> runAfterBothAsync(CompletionStage<?> other,
Runnable action,
Executor executor) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageexecutor - the executor to use for asynchronous execution<U> CompletionStage<U> applyToEither(CompletionStage<? extends T> other,
Function<? super T,U> fn) 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.
U - the function's return typeother - the other CompletionStagefn - the function to use to compute the value of the returned CompletionStage<U> CompletionStage<U> applyToEitherAsync(CompletionStage<? extends T> other,
Function<? super T,U> fn) 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.
U - the function's return typeother - the other CompletionStagefn - the function to use to compute the value of the returned CompletionStage<U> CompletionStage<U> applyToEitherAsync(CompletionStage<? extends T> other,
Function<? super T,U> fn,
Executor executor) 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.
U - the function's return typeother - the other CompletionStagefn - the function to use to compute the value of the returned CompletionStageexecutor - the executor to use for asynchronous executionCompletionStage<Void> acceptEither(CompletionStage<? extends T> other,
Consumer<? super T> action) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageCompletionStage<Void> acceptEitherAsync(CompletionStage<? extends T> other,
Consumer<? super T> action) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageCompletionStage<Void> acceptEitherAsync(CompletionStage<? extends T> other,
Consumer<? super T> action,
Executor executor) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageexecutor - the executor to use for asynchronous executionCompletionStage<Void> runAfterEither(CompletionStage<?> other,
Runnable action) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageCompletionStage<Void> runAfterEitherAsync(CompletionStage<?> other,
Runnable action) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageCompletionStage<Void> runAfterEitherAsync(CompletionStage<?> other,
Runnable action,
Executor executor) 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.
other - the other CompletionStageaction - the action to perform before completing the returned CompletionStageexecutor - the executor to use for asynchronous execution<U> CompletionStage<U> thenCompose(Function<? super T,? extends CompletionStage<U>> fn)
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.
U - the type of the returned CompletionStage's resultfn - the function returning a new CompletionStage<U> CompletionStage<U> thenComposeAsync(Function<? super T,? extends CompletionStage<U>> fn)
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.
U - the type of the returned CompletionStage's resultfn - the function returning a new CompletionStage<U> CompletionStage<U> thenComposeAsync(Function<? super T,? extends CompletionStage<U>> fn,
Executor executor) 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.
U - the type of the returned CompletionStage's resultfn - the function returning a new CompletionStageexecutor - the executor to use for asynchronous executionCompletionStage<T> exceptionally(Function<Throwable,? extends T> fn)
Returns a new CompletionStage that, when this stage completes exceptionally, is executed with this stage's exception as the argument to the supplied function. Otherwise, if this stage completes normally, then the returned stage also completes normally with the same value.
fn - the function to use to compute the value of the returned CompletionStage if this CompletionStage completed exceptionallyCompletionStage<T> whenComplete(BiConsumer<? super T,? super Throwable> action)
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.
action - the action to performCompletionStage<T> whenCompleteAsync(BiConsumer<? super T,? super Throwable> action)
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.
action - the action to performCompletionStage<T> whenCompleteAsync(BiConsumer<? super T,? super Throwable> action,
Executor executor) 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.
action - the action to performexecutor - the executor to use for asynchronous execution<U> CompletionStage<U> handle(BiFunction<? super T,Throwable,? extends U> fn)
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.
U - the function's return typefn - the function to use to compute the value of the returned CompletionStage<U> CompletionStage<U> handleAsync(BiFunction<? super T,Throwable,? extends U> fn)
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.
U - the function's return typefn - the function to use to compute the value of the returned CompletionStage<U> CompletionStage<U> handleAsync(BiFunction<? super T,Throwable,? extends U> fn,
Executor executor) 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.
U - the function's return typefn - the function to use to compute the value of the returned CompletionStageexecutor - the executor to use for asynchronous executionCompletableFuture<T> toCompletableFuture()
Returns a CompletableFuture maintaining the same completion properties as this stage. If this stage is already a CompletableFuture, this method may return this stage itself. Otherwise, invocation of this method may be equivalent in effect to thenApply(x -> x), but returning an instance of type CompletableFuture. A CompletionStage implementation that does not choose to interoperate with others may throw UnsupportedOperationException.
UnsupportedOperationException - if this implementation does not interoperate with CompletableFuture
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