Module io.helidon.common.reactive

Package io.helidon.common.reactive

Interface Multi<T>

Type Parameters:

T - item type

All Superinterfaces:

Flow.Publisher<T>, Subscribable<T>

All Known Implementing Classes:

ConcatPublisher, MultiFromOutputStream, MultiTappedPublisher, OutputStreamMulti

public interface Multi<T>
extends Subscribable<T>

Represents a Flow.Publisher emitting zero or more items, optionally followed by an error or completion.

See Also:

• Single

Method Summary

Modifier and Type	Method	Description
default <U> Single<U>	collect(Collector<T,U> collector)	Collect the items of this Multi instance into a Single.
default <U> Single<U>	collect(Supplier<? extends U> collectionSupplier, BiConsumer<U,T> accumulator)	Collect the items of this Multi into a collection provided via a Supplier and mutated by a BiConsumer callback.
default Single<List<T>>	collectList()	Collect the items of this Multi instance into a Single of List.
default <A, R> Single<R>	collectStream(Collector<T,A,R> collector)	Collects up upstream items with the help of a the callbacks of a Collector.
default <U> Multi<U>	compose(Function<? super Multi<T>,? extends Flow.Publisher<? extends U>> composer)	Apply the given composer function to the current Multi instance and return aMulti wrapping the returned Flow.Publisher of this function.
static <T> Multi<T>	concat(Flow.Publisher<T> firstMulti, Flow.Publisher<T> secondMulti)	Concat streams to one.
static <T> Multi<T>	concat(Flow.Publisher<T> firstPublisher, Flow.Publisher<T> secondPublisher, Flow.Publisher<T>... morePublishers)	Concat streams to one.
static <T> Multi<T>	concatArray(Flow.Publisher<T>... publishers)	Concatenates an array of source Flow.Publishers by relaying items in order, non-overlappingly, one after the other finishes.
static <T> Multi<T>	create(Single<T> single)	Create a Multi instance wrapped around the given Single.
static <T> Multi<T>	create(Iterable<T> iterable)	Create a Multi instance that publishes the given iterable.
static <T> Multi<T>	create(CompletionStage<T> completionStage)	Wrap a CompletionStage into a Multi and signal its outcome non-blockingly.
static <T> Multi<T>	create(CompletionStage<T> completionStage, boolean nullMeansEmpty)	Wrap a CompletionStage into a Multi and signal its outcome non-blockingly.
static <T> Multi<T>	create(Flow.Publisher<T> source)	Create a Multi instance wrapped around the given publisher.
static <T> Multi<T>	create(Stream<T> stream)	Create a Multi instance that publishes the given Stream.
default Multi<T>	defaultIfEmpty(Supplier<? extends T> supplier)	Signals the default item supplied by specified supplier if the upstream is empty.
default Multi<T>	defaultIfEmpty(T defaultItem)	Signals the default item if the upstream is empty.
static <T> Multi<T>	defer(Supplier<? extends Flow.Publisher<? extends T>> supplier)	Call the given supplier function for each individual downstream Subscriber to return a Flow.Publisher to subscribe to.
default Multi<T>	distinct()	Filter out all duplicates.
default Multi<T>	dropWhile(Predicate<? super T> predicate)	Drop the longest prefix of elements from this stream that satisfy the given predicate.
static <T> Multi<T>	empty()	Get a Multi instance that completes immediately.
static <T> Multi<T>	error(Throwable error)	Create a Multi instance that reports the given exception to its subscriber(s).
default Multi<T>	filter(Predicate<? super T> predicate)	Filter stream items with provided predicate.
default Single<T>	first()	Get the first item of this Multi instance as a Single.
default <U> Multi<U>	flatMap(Function<? super T,? extends Flow.Publisher<? extends U>> publisherMapper)	Transform item with supplied function and flatten resulting Flow.Publisher to downstream.
default <U> Multi<U>	flatMap(Function<? super T,? extends Flow.Publisher<? extends U>> mapper, long maxConcurrency, boolean delayErrors, long prefetch)	Transform item with supplied function and flatten resulting Flow.Publisher to downstream while limiting the maximum number of concurrent inner Flow.Publishers and their in-flight item count, optionally aggregating and delaying all errors until all sources terminate.
default <U> Multi<U>	flatMapCompletionStage(Function<? super T,? extends CompletionStage<? extends U>> mapper)	Transform item with supplied function and flatten resulting CompletionStage results to downstream.
default <U> Multi<U>	flatMapIterable(Function<? super T,? extends Iterable<? extends U>> iterableMapper)	Transform item with supplied function and flatten resulting Iterable to downstream.
default <U> Multi<U>	flatMapIterable(Function<? super T,? extends Iterable<? extends U>> iterableMapper, int prefetch)	Transform item with supplied function and flatten resulting Iterable to downstream.
default <U> Multi<U>	flatMapOptional(Function<? super T,Optional<? extends U>> mapper)	Transform item with supplied function and flatten resulting Optional to downstream as one item if present or nothing if empty.
default Single<Void>	forEach(Consumer<? super T> consumer)	Terminal stage, invokes provided consumer for every item in the stream with no backpressure.
default Single<Void>	forEachCompletionStage(Function<? super T,CompletionStage<Void>> function)	Terminal stage, invokes provided consumer for every item in the stream with strict backpressure.
static <T> Multi<T>	from(Single<T> single)	Deprecated. use create(io.helidon.common.reactive.Single) instead
static <T> Multi<T>	from(Iterable<T> iterable)	Deprecated. use create(java.lang.Iterable) instead
static <T> Multi<T>	from(CompletionStage<T> completionStage)	Deprecated. use create(java.util.concurrent.CompletionStage) instead
static <T> Multi<T>	from(CompletionStage<T> completionStage, boolean nullMeansEmpty)	Deprecated. use create(java.util.concurrent.CompletionStage, boolean) instead
static <T> Multi<T>	from(Flow.Publisher<T> source)	Deprecated. use create(java.util.concurrent.Flow.Publisher) instead
static <T> Multi<T>	from(Stream<T> stream)	Deprecated. use create(java.util.stream.Stream) instead
default Multi<T>	ifEmpty(Runnable ifEmpty)	Executes given Runnable when stream is finished without value(empty stream).
default Single<Void>	ignoreElements()	Terminal stage, ignore all items and complete returned Single<Void> successfully or exceptionally.
static Multi<Long>	interval(long initialDelay, long period, TimeUnit unit, ScheduledExecutorService executor)	Signal 0L after an initial delay, then 1L, 2L and so on periodically to the downstream.
static Multi<Long>	interval(long period, TimeUnit unit, ScheduledExecutorService executor)	Signal 0L, 1L and so on periodically to the downstream.
static <T> Multi<T>	just(Collection<T> items)	Create a Multi instance that publishes the given items to a single subscriber.
static <T> Multi<T>	just(T... items)	Create a Multi instance that publishes the given items to a single subscriber.
default Multi<T>	limit(long limit)	Limit stream to allow only specified number of items to pass.
default Multi<T>	log()	Log all signals onSubscribe, onNext, onError, onComplete, cancel and request coming to and from preceding operator.
default Multi<T>	log(Level level)	Log all signals onSubscribe, onNext, onError, onComplete, cancel and request coming to and from preceding operator.
default Multi<T>	log(Level level, boolean trace)	Log all signals onSubscribe, onNext, onError, onComplete, cancel and request coming to and from preceding operator.
default Multi<T>	log(Level level, String loggerName)	Log all signals onSubscribe, onNext, onError, onComplete, cancel and request coming to and from preceding operator.
default <U> Multi<U>	map(Function<? super T,? extends U> mapper)	Map this Multi instance to a new Multi of another type using the given Function.
static <T> Multi<T>	never()	Get a Multi instance that never completes.
default Multi<T>	observeOn(Executor executor)	Re-emit the upstream's signals to the downstream on the given executor's thread using a default buffer size of 32 and errors skipping ahead of items.
default Multi<T>	observeOn(Executor executor, int bufferSize, boolean delayError)	Re-emit the upstream's signals to the downstream on the given executor's thread.
default Multi<T>	onCancel(Runnable onCancel)	Executes given Runnable when a cancel signal is received.
default Multi<T>	onComplete(Runnable onComplete)	Executes given Runnable when onComplete signal is received.
default Multi<T>	onCompleteResume(T item)	Resume stream from single item if onComplete signal is intercepted.
default Multi<T>	onCompleteResumeWith(Flow.Publisher<? extends T> publisher)	Resume stream from supplied publisher if onComplete signal is intercepted.
default Multi<T>	onError(Consumer<? super Throwable> onErrorConsumer)	Executes given Runnable when onError signal is received.
default Multi<T>	onErrorResume(Function<? super Throwable,? extends T> onError)	Function providing one item to be submitted as onNext in case of onError signal is received.
default Multi<T>	onErrorResumeWith(Function<? super Throwable,? extends Flow.Publisher<? extends T>> onError)	Resume stream from supplied publisher if onError signal is intercepted.
default Multi<T>	onTerminate(Runnable onTerminate)	Executes given Runnable when any of signals onComplete, onCancel or onError is received.
default Multi<T>	peek(Consumer<? super T> consumer)	Invoke provided consumer for every item in stream.
static Multi<Integer>	range(int start, int count)	Emits a range of ever increasing integers.
static Multi<Long>	rangeLong(long start, long count)	Emits a range of ever increasing longs.
default Single<T>	reduce(BiFunction<T,T,T> reducer)	Combine subsequent items via a callback function and emit the final value result as a Single.
default <R> Single<R>	reduce(Supplier<? extends R> supplier, BiFunction<R,T,R> reducer)	Combine every upstream item with an accumulator value to produce a new accumulator value and emit the final accumulator value as a Single.
default Multi<T>	retry(long count)	Retry a failing upstream at most the given number of times before giving up.
default Multi<T>	retry(BiPredicate<? super Throwable,? super Long> predicate)	Retry a failing upstream if the predicate returns true.
default <U> Multi<T>	retryWhen(BiFunction<? super Throwable,? super Long,? extends Flow.Publisher<U>> whenFunction)	Retry a failing upstream when the given function returns a publisher that signals an item.
static <T> Multi<T>	singleton(T item)	Create a Multi that emits a pre-existing item and then completes.
default Multi<T>	skip(long skip)	Skip first n items, all the others are emitted.
default Multi<T>	switchIfEmpty(Flow.Publisher<T> other)	Switch to the other publisher if the upstream is empty.
default <U> Multi<T>	takeUntil(Flow.Publisher<U> other)	Relay upstream items until the other source signals an item or completes.
default Multi<T>	takeWhile(Predicate<? super T> predicate)	Take the longest prefix of elements from this stream that satisfy the given predicate.
default Multi<T>	timeout(long timeout, TimeUnit unit, ScheduledExecutorService executor)	Signals a TimeoutException if the upstream doesn't signal the next item, error or completion within the specified time.
default Multi<T>	timeout(long timeout, TimeUnit unit, ScheduledExecutorService executor, Flow.Publisher<T> fallback)	Switches to a fallback single if the upstream doesn't signal the next item, error or completion within the specified time.
static Multi<Long>	timer(long time, TimeUnit unit, ScheduledExecutorService executor)	Signal 0L and complete the sequence after the given time elapsed.
default <U> U	to(Function<? super Multi<T>,? extends U> converter)	Apply the given converter function to the current Multi instance and return the value returned by this function.

Methods inherited from interface java.util.concurrent.Flow.Publisher

subscribe

Methods inherited from interface io.helidon.common.reactive.Subscribable

subscribe, subscribe, subscribe, subscribe

Method Details

concat

static <T> Multi<T> concat(Flow.Publisher<T> firstMulti,
 Flow.Publisher<T> secondMulti)

Concat streams to one.

Type Parameters:

T - item type

Parameters:

firstMulti - first stream

secondMulti - second stream

Returns:

Multi

concat

@SafeVarargs
static <T> Multi<T> concat(Flow.Publisher<T> firstPublisher,
 Flow.Publisher<T> secondPublisher,
 Flow.Publisher<T>... morePublishers)

Concat streams to one.

Type Parameters:

T - item type

Parameters:

firstPublisher - first stream

secondPublisher - second stream

morePublishers - more publishers to concat

Returns:

Multi

concatArray

@SafeVarargs
static <T> Multi<T> concatArray(Flow.Publisher<T>... publishers)

Concatenates an array of source Flow.Publishers by relaying items in order, non-overlappingly, one after the other finishes.

Type Parameters:

T - item type

Parameters:

publishers - more publishers to concat

Returns:

Multi

defer

static <T> Multi<T> defer(Supplier<? extends Flow.Publisher<? extends T>> supplier)

Call the given supplier function for each individual downstream Subscriber to return a Flow.Publisher to subscribe to.

Type Parameters:

T - the element type of the sequence

Parameters:

supplier - the callback to return a Flow.Publisher for each Subscriber

Returns:

Multi

Throws:

NullPointerException - if supplier is null

empty

static <T> Multi<T> empty()

Get a Multi instance that completes immediately.

Type Parameters:

T - item type

Returns:

Multi

error

static <T> Multi<T> error(Throwable error)

Create a Multi instance that reports the given exception to its subscriber(s). The exception is reported by invoking Flow.Subscriber.onError(java.lang.Throwable) when Flow.Publisher.subscribe(Subscriber) is called.

Type Parameters:

T - item type

Parameters:

error - exception to hold

Returns:

Multi

Throws:

NullPointerException - if error is null

from

@Deprecated
static <T> Multi<T> from(CompletionStage<T> completionStage)

Deprecated.

use create(java.util.concurrent.CompletionStage) instead

Wrap a CompletionStage into a Multi and signal its outcome non-blockingly.

A null result from the CompletionStage will yield a NullPointerException signal.

Type Parameters:

T - the element type of the stage and result

Parameters:

completionStage - the CompletionStage to

Returns:

Multi

See Also:

• create(CompletionStage, boolean)

from

@Deprecated
static <T> Multi<T> from(CompletionStage<T> completionStage,
 boolean nullMeansEmpty)

Deprecated.

use create(java.util.concurrent.CompletionStage, boolean) instead

Wrap a CompletionStage into a Multi and signal its outcome non-blockingly.

Type Parameters:

T - the element type of the stage and result

Parameters:

completionStage - the CompletionStage to

nullMeansEmpty - if true, a null result is interpreted to be an empty sequence if false, the resulting sequence fails with NullPointerException

Returns:

Multi

from

@Deprecated
static <T> Multi<T> from(Iterable<T> iterable)

Deprecated.

use create(java.lang.Iterable) instead

Create a Multi instance that publishes the given iterable.

Type Parameters:

T - item type

Parameters:

iterable - iterable to publish

Returns:

Multi

Throws:

NullPointerException - if iterable is null

from

@Deprecated
static <T> Multi<T> from(Flow.Publisher<T> source)

Deprecated.

use create(java.util.concurrent.Flow.Publisher) instead

Create a Multi instance wrapped around the given publisher.

Type Parameters:

T - item type

Parameters:

source - source publisher

Returns:

Multi

Throws:

NullPointerException - if source is null

from

@Deprecated
static <T> Multi<T> from(Single<T> single)

Deprecated.

use create(io.helidon.common.reactive.Single) instead

Create a Multi instance wrapped around the given Single.

Type Parameters:

T - item type

Parameters:

single - source Single publisher

Returns:

Multi

Throws:

NullPointerException - if source is null

from

@Deprecated
static <T> Multi<T> from(Stream<T> stream)

Deprecated.

use create(java.util.stream.Stream) instead

Create a Multi instance that publishes the given Stream.

Note that Streams can be only consumed once, therefore, the returned Multi will signal IllegalStateException if multiple subscribers try to consume it.

The operator calls BaseStream.close() when the stream finishes, fails or the flow gets canceled. To avoid closing the stream automatically, it is recommended to turn the Stream into an Iterable via BaseStream.iterator() and use create(Iterable):

     Stream<T> stream = ...
     Multi<T> multi = Multi.create(stream::iterator);
     

Type Parameters:

T - item type

Parameters:

stream - the Stream to publish

Returns:

Multi

Throws:

NullPointerException - if stream is null

create

static <T> Multi<T> create(CompletionStage<T> completionStage)

Wrap a CompletionStage into a Multi and signal its outcome non-blockingly.

A null result from the CompletionStage will yield a NullPointerException signal.

Type Parameters:

T - the element type of the stage and result

Parameters:

completionStage - the CompletionStage to

Returns:

Multi

See Also:

• create(CompletionStage, boolean)

create

static <T> Multi<T> create(CompletionStage<T> completionStage,
 boolean nullMeansEmpty)

Wrap a CompletionStage into a Multi and signal its outcome non-blockingly.

Type Parameters:

T - the element type of the stage and result

Parameters:

completionStage - the CompletionStage to

nullMeansEmpty - if true, a null result is interpreted to be an empty sequence if false, the resulting sequence fails with NullPointerException

Returns:

Multi

create

static <T> Multi<T> create(Iterable<T> iterable)

Create a Multi instance that publishes the given iterable.

Type Parameters:

T - item type

Parameters:

iterable - iterable to publish

Returns:

Multi

Throws:

NullPointerException - if iterable is null

create

static <T> Multi<T> create(Flow.Publisher<T> source)

Create a Multi instance wrapped around the given publisher.

Type Parameters:

T - item type

Parameters:

source - source publisher

Returns:

Multi

Throws:

NullPointerException - if source is null

create

static <T> Multi<T> create(Single<T> single)

Create a Multi instance wrapped around the given Single.

Type Parameters:

T - item type

Parameters:

single - source Single publisher

Returns:

Multi

Throws:

NullPointerException - if source is null

create

static <T> Multi<T> create(Stream<T> stream)

Create a Multi instance that publishes the given Stream.

Note that Streams can be only consumed once, therefore, the returned Multi will signal IllegalStateException if multiple subscribers try to consume it.

The operator calls BaseStream.close() when the stream finishes, fails or the flow gets canceled. To avoid closing the stream automatically, it is recommended to turn the Stream into an Iterable via BaseStream.iterator() and use create(Iterable):

     Stream<T> stream = ...
     Multi<T> multi = Multi.create(stream::iterator);
     

Type Parameters:

T - item type

Parameters:

stream - the Stream to publish

Returns:

Multi

Throws:

NullPointerException - if stream is null

interval

static Multi<Long> interval(long period,
 TimeUnit unit,
 ScheduledExecutorService executor)

Signal 0L, 1L and so on periodically to the downstream.

Note that if the downstream applies backpressure, subsequent values may be delivered instantly upon further requests from the downstream.

Parameters:

period - the initial and in-between time

unit - the time unit

executor - the scheduled executor to use for the periodic emission

Returns:

Multi

Throws:

NullPointerException - if unit or executor is null

interval

static Multi<Long> interval(long initialDelay,
 long period,
 TimeUnit unit,
 ScheduledExecutorService executor)

Signal 0L after an initial delay, then 1L, 2L and so on periodically to the downstream.

Note that if the downstream applies backpressure, subsequent values may be delivered instantly upon further requests from the downstream.

Parameters:

initialDelay - the time before signaling 0L

period - the in-between wait time for values 1L, 2L and so on

unit - the time unit

executor - the scheduled executor to use for the periodic emission

Returns:

Multi

Throws:

NullPointerException - if unit or executor is null

just

static <T> Multi<T> just(Collection<T> items)

Create a Multi instance that publishes the given items to a single subscriber.

Type Parameters:

T - item type

Parameters:

items - items to publish

Returns:

Multi

Throws:

NullPointerException - if items is null

just

@SafeVarargs
static <T> Multi<T> just(T... items)

Create a Multi instance that publishes the given items to a single subscriber.

Type Parameters:

T - item type

Parameters:

items - items to publish

Returns:

Multi

Throws:

NullPointerException - if items is null

never

static <T> Multi<T> never()

Get a Multi instance that never completes.

Type Parameters:

T - item type

Returns:

Multi

range

static Multi<Integer> range(int start,
 int count)

Emits a range of ever increasing integers.

Parameters:

start - the initial integer value

count - the number of integers to emit

Returns:

Multi

Throws:

IllegalArgumentException - if count is negative

rangeLong

static Multi<Long> rangeLong(long start,
 long count)

Emits a range of ever increasing longs.

Parameters:

start - the initial long value

count - the number of longs to emit

Returns:

Multi

Throws:

IllegalArgumentException - if count is negative

singleton

static <T> Multi<T> singleton(T item)

Create a Multi that emits a pre-existing item and then completes.

Type Parameters:

T - the type of the item

Parameters:

item - the item to emit.

Returns:

Multi

Throws:

NullPointerException - if item is null

timer

static Multi<Long> timer(long time,
 TimeUnit unit,
 ScheduledExecutorService executor)

Signal 0L and complete the sequence after the given time elapsed.

Parameters:

time - the time to wait before signaling 0L and completion

unit - the unit of time

executor - the executor to run the waiting on

Returns:

Multi

Throws:

NullPointerException - if unit or executor is null

collect

default <U> Single<U> collect(Collector<T,U> collector)

Collect the items of this Multi instance into a Single.

Type Parameters:

U - collector container type

Parameters:

collector - collector to use

Returns:

Single

Throws:

NullPointerException - if collector is null

collect

default <U> Single<U> collect(Supplier<? extends U> collectionSupplier,
 BiConsumer<U,T> accumulator)

Collect the items of this Multi into a collection provided via a Supplier and mutated by a BiConsumer callback.

Type Parameters:

U - the type of the collection and result

Parameters:

collectionSupplier - the Supplier that is called for each incoming Flow.Subscriber to create a fresh collection to collect items into

accumulator - the BiConsumer that receives the collection and the current item to put in

Returns:

Single

Throws:

NullPointerException - if collectionSupplier or combiner is null

collectList

default Single<List<T>> collectList()

Collect the items of this Multi instance into a Single of List.

Returns:

Single

collectStream

default <A,
R> Single<R> collectStream(Collector<T,A,R> collector)

Collects up upstream items with the help of a the callbacks of a Collector.

Type Parameters:

A - the accumulator type

R - the result type

Parameters:

collector - the collector whose supplier(), accumulator() and finisher() callbacks are used for collecting upstream items into a final form.

Returns:

Single

Throws:

NullPointerException - if collector is null

compose

default <U> Multi<U> compose(Function<? super Multi<T>,? extends Flow.Publisher<? extends U>> composer)

Apply the given composer function to the current Multi instance and return aMulti wrapping the returned Flow.Publisher of this function.

Note that the composer function is executed upon calling this method immediately and not when the resulting sequence gets subscribed to.

Type Parameters:

U - the output element type

Parameters:

composer - the function that receives the current Multi instance and should return a Flow.Publisher to be wrapped into a Multie to be returned by the method

Returns:

Multi

Throws:

NullPointerException - if composer is null

defaultIfEmpty

default Multi<T> defaultIfEmpty(T defaultItem)

Signals the default item if the upstream is empty.

Specified by:

defaultIfEmpty in interface Subscribable<T>

Parameters:

defaultItem - the item to signal if the upstream is empty

Returns:

Multi

Throws:

NullPointerException - if defaultItem is null

defaultIfEmpty

default Multi<T> defaultIfEmpty(Supplier<? extends T> supplier)

Signals the default item supplied by specified supplier if the upstream is empty.

Specified by:

defaultIfEmpty in interface Subscribable<T>

Parameters:

supplier - of the default value

Returns:

Multi

Throws:

NullPointerException - if supplier is null

distinct

default Multi<T> distinct()

Filter out all duplicates.

Returns:

Multi

dropWhile

default Multi<T> dropWhile(Predicate<? super T> predicate)

Drop the longest prefix of elements from this stream that satisfy the given predicate. As long as predicate returns true, items from upstream are NOT sent to downstream but being dropped, predicate is never called again after it returns false for the first time.

Parameters:

predicate - predicate to filter stream with

Returns:

Multi

filter

default Multi<T> filter(Predicate<? super T> predicate)

Filter stream items with provided predicate.

Parameters:

predicate - predicate to filter stream with

Returns:

Multi

first

default Single<T> first()

Get the first item of this Multi instance as a Single.

Returns:

Single

flatMap

default <U> Multi<U> flatMap(Function<? super T,? extends Flow.Publisher<? extends U>> publisherMapper)

Transform item with supplied function and flatten resulting Flow.Publisher to downstream.

Specified by:

flatMap in interface Subscribable<T>

Type Parameters:

U - output item type

Parameters:

publisherMapper - Function receiving item as parameter and returning Flow.Publisher

Returns:

Multi

flatMap

default <U> Multi<U> flatMap(Function<? super T,? extends Flow.Publisher<? extends U>> mapper,
 long maxConcurrency,
 boolean delayErrors,
 long prefetch)

Transform item with supplied function and flatten resulting Flow.Publisher to downstream while limiting the maximum number of concurrent inner Flow.Publishers and their in-flight item count, optionally aggregating and delaying all errors until all sources terminate.

Type Parameters:

U - output item type

Parameters:

mapper - Function receiving item as parameter and returning Flow.Publisher

maxConcurrency - the maximum number of inner sources to run

delayErrors - if true, any error from the main and inner sources are aggregated and delayed until all of them terminate

prefetch - the number of items to request upfront from the inner sources, then request 75% more after 75% has been delivered

Returns:

Multi

flatMapCompletionStage

default <U> Multi<U> flatMapCompletionStage(Function<? super T,? extends CompletionStage<? extends U>> mapper)

Transform item with supplied function and flatten resulting CompletionStage results to downstream. As reactive streams forbids null values, error signal with NullPointerException is sent to downstream when CompletionStage result is null.

Type Parameters:

U - output item type

Parameters:

mapper - Function receiving item as parameter and returning CompletionStage

Returns:

Multi

Throws:

NullPointerException - if mapper is null

flatMapIterable

default <U> Multi<U> flatMapIterable(Function<? super T,? extends Iterable<? extends U>> iterableMapper)

Transform item with supplied function and flatten resulting Iterable to downstream.

Specified by:

flatMapIterable in interface Subscribable<T>

Type Parameters:

U - output item type

Parameters:

iterableMapper - Function receiving item as parameter and returning Iterable

Returns:

Multi

flatMapIterable

default <U> Multi<U> flatMapIterable(Function<? super T,? extends Iterable<? extends U>> iterableMapper,
 int prefetch)

Transform item with supplied function and flatten resulting Iterable to downstream.

Type Parameters:

U - output item type

Parameters:

iterableMapper - Function receiving item as parameter and returning Iterable

prefetch - the number of upstream items to request upfront, then 75% of this value after 75% received and mapped

Returns:

Multi

flatMapOptional

default <U> Multi<U> flatMapOptional(Function<? super T,Optional<? extends U>> mapper)

Transform item with supplied function and flatten resulting Optional to downstream as one item if present or nothing if empty.

Type Parameters:

U - output item type

Parameters:

mapper - Function receiving item as parameter and returning Optional

Returns:

Multi

limit

default Multi<T> limit(long limit)

Limit stream to allow only specified number of items to pass.

Parameters:

limit - with expected number of items to be produced

Returns:

Multi

map

default <U> Multi<U> map(Function<? super T,? extends U> mapper)

Map this Multi instance to a new Multi of another type using the given Function.

Specified by:

map in interface Subscribable<T>

Type Parameters:

U - mapped item type

Parameters:

mapper - mapper

Returns:

Multi

Throws:

NullPointerException - if mapper is null

observeOn

default Multi<T> observeOn(Executor executor)

Re-emit the upstream's signals to the downstream on the given executor's thread using a default buffer size of 32 and errors skipping ahead of items.

Specified by:

observeOn in interface Subscribable<T>

Parameters:

executor - the executor to signal the downstream from.

Returns:

Multi

Throws:

NullPointerException - if executor is null

See Also:

• observeOn(Executor, int, boolean)

observeOn

default Multi<T> observeOn(Executor executor,
 int bufferSize,
 boolean delayError)

Re-emit the upstream's signals to the downstream on the given executor's thread.

Parameters:

executor - the executor to signal the downstream from.

bufferSize - the number of items to prefetch and buffer at a time

delayError - if true, errors are emitted after items, if false, errors may cut ahead of items during emission

Returns:

Multi

Throws:

NullPointerException - if executor is null

onCancel

default Multi<T> onCancel(Runnable onCancel)

Executes given Runnable when a cancel signal is received.

Specified by:

onCancel in interface Subscribable<T>

Parameters:

onCancel - Runnable to be executed.

Returns:

Multi

onComplete

default Multi<T> onComplete(Runnable onComplete)

Executes given Runnable when onComplete signal is received.

Specified by:

onComplete in interface Subscribable<T>

Parameters:

onComplete - Runnable to be executed.

Returns:

Multi

onError

default Multi<T> onError(Consumer<? super Throwable> onErrorConsumer)

Executes given Runnable when onError signal is received.

Specified by:

onError in interface Subscribable<T>

Parameters:

onErrorConsumer - Consumer to be executed.

Returns:

Multi

onErrorResume

default Multi<T> onErrorResume(Function<? super Throwable,? extends T> onError)

Function providing one item to be submitted as onNext in case of onError signal is received.

Specified by:

onErrorResume in interface Subscribable<T>

Parameters:

onError - Function receiving Throwable as argument and producing one item to resume stream with.

Returns:

Multi

onErrorResumeWith

default Multi<T> onErrorResumeWith(Function<? super Throwable,? extends Flow.Publisher<? extends T>> onError)

Resume stream from supplied publisher if onError signal is intercepted.

Specified by:

onErrorResumeWith in interface Subscribable<T>

Parameters:

onError - supplier of new stream publisher

Returns:

Multi

onCompleteResume

default Multi<T> onCompleteResume(T item)

Resume stream from single item if onComplete signal is intercepted. Effectively do an append to the stream.

Specified by:

onCompleteResume in interface Subscribable<T>

Parameters:

item - one item to resume stream with

Returns:

Multi

onCompleteResumeWith

default Multi<T> onCompleteResumeWith(Flow.Publisher<? extends T> publisher)

Resume stream from supplied publisher if onComplete signal is intercepted.

Specified by:

onCompleteResumeWith in interface Subscribable<T>

Parameters:

publisher - new stream publisher

Returns:

Multi

onTerminate

default Multi<T> onTerminate(Runnable onTerminate)

Executes given Runnable when any of signals onComplete, onCancel or onError is received.

Specified by:

onTerminate in interface Subscribable<T>

Parameters:

onTerminate - Runnable to be executed.

Returns:

Multi

ifEmpty

default Multi<T> ifEmpty(Runnable ifEmpty)

Executes given Runnable when stream is finished without value(empty stream).

Parameters:

ifEmpty - Runnable to be executed.

Returns:

Multi

peek

default Multi<T> peek(Consumer<? super T> consumer)

Invoke provided consumer for every item in stream.

Specified by:

peek in interface Subscribable<T>

Parameters:

consumer - consumer to be invoked

Returns:

Multi

log

default Multi<T> log()

Log all signals onSubscribe, onNext, onError, onComplete, cancel and request coming to and from preceding operator.

Returns:

Multi

log

default Multi<T> log(Level level)

Log all signals onSubscribe, onNext, onError, onComplete, cancel and request coming to and from preceding operator.

Parameters:

level - a logging level value

Returns:

Multi

log

default Multi<T> log(Level level,
 String loggerName)

Log all signals onSubscribe, onNext, onError, onComplete, cancel and request coming to and from preceding operator.

Parameters:

level - a logging level value

loggerName - custom logger name

Returns:

Multi

log

default Multi<T> log(Level level,
 boolean trace)

Log all signals onSubscribe, onNext, onError, onComplete, cancel and request coming to and from preceding operator.

Enabled trace option has a negative impact on performance and should NOT be used in production.

Parameters:

level - a logging level value

trace - if true position of operator is looked up from stack and logged

Returns:

Multi

reduce

default Single<T> reduce(BiFunction<T,T,T> reducer)

Combine subsequent items via a callback function and emit the final value result as a Single.

If the upstream is empty, the resulting Single is also empty. If the upstream contains only one item, the reducer function is not invoked and the resulting Single will have only that single item.

Parameters:

reducer - the function called with the first value or the previous result, the current upstream value and should return a new value

Returns:

Single

reduce

default <R> Single<R> reduce(Supplier<? extends R> supplier,
 BiFunction<R,T,R> reducer)

Combine every upstream item with an accumulator value to produce a new accumulator value and emit the final accumulator value as a Single.

Type Parameters:

R - the accumulator and result type

Parameters:

supplier - the function to return the initial accumulator value for each incoming Subscriber

reducer - the function that receives the current accumulator value, the current upstream value and should return a new accumulator value

Returns:

Single

retry

default Multi<T> retry(long count)

Retry a failing upstream at most the given number of times before giving up.

Specified by:

retry in interface Subscribable<T>

Parameters:

count - the number of times to retry; 0 means no retry at all

Returns:

Multi

Throws:

IllegalArgumentException - if count is negative

See Also:

• retryWhen(BiFunction)

retry

default Multi<T> retry(BiPredicate<? super Throwable,? super Long> predicate)

Retry a failing upstream if the predicate returns true.

Specified by:

retry in interface Subscribable<T>

Parameters:

predicate - the predicate that receives the latest failure Throwable the number of times the retry happened so far (0-based) and should return true to retry the upstream again or false to signal the latest failure

Returns:

Multi

Throws:

NullPointerException - if predicate is null

See Also:

• retryWhen(BiFunction)

retryWhen

default <U> Multi<T> retryWhen(BiFunction<? super Throwable,? super Long,? extends Flow.Publisher<U>> whenFunction)

Retry a failing upstream when the given function returns a publisher that signals an item.

If the publisher returned by the function completes, the repetition stops and this Multi is completed. If the publisher signals an error, the repetition stops and this Multi will signal this error.

Specified by:

retryWhen in interface Subscribable<T>

Type Parameters:

U - the element type of the retry-signal sequence

Parameters:

whenFunction - the function that receives the latest failure Throwable the number of times the retry happened so far (0-based) and should return a Flow.Publisher that should signal an item to retry again, complete to stop and complete this Multi or signal an error to have this Multi emit that error as well.

Returns:

Multi

Throws:

NullPointerException - if whenFunction is null

skip

default Multi<T> skip(long skip)

Skip first n items, all the others are emitted.

Parameters:

skip - number of items to be skipped

Returns:

Multi

switchIfEmpty

default Multi<T> switchIfEmpty(Flow.Publisher<T> other)

Switch to the other publisher if the upstream is empty.

Parameters:

other - the publisher to switch to if the upstream is empty.

Returns:

Multi

Throws:

NullPointerException - if other is null

takeUntil

default <U> Multi<T> takeUntil(Flow.Publisher<U> other)

Relay upstream items until the other source signals an item or completes.

Specified by:

takeUntil in interface Subscribable<T>

Type Parameters:

U - the element type of the other sequence

Parameters:

other - the other sequence to signal the end of the main sequence

Returns:

Multi

Throws:

NullPointerException - if other is null

takeWhile

default Multi<T> takeWhile(Predicate<? super T> predicate)

Take the longest prefix of elements from this stream that satisfy the given predicate. As long as predicate returns true, items from upstream are sent to downstream, when predicate returns false stream is completed.

Parameters:

predicate - predicate to filter stream with

Returns:

Multi

timeout

default Multi<T> timeout(long timeout,
 TimeUnit unit,
 ScheduledExecutorService executor)

Signals a TimeoutException if the upstream doesn't signal the next item, error or completion within the specified time.

Specified by:

timeout in interface Subscribable<T>

Parameters:

timeout - the time to wait for the upstream to signal

unit - the time unit

executor - the executor to use for waiting for the upstream signal

Returns:

Multi

Throws:

NullPointerException - if unit or executor is null

timeout

default Multi<T> timeout(long timeout,
 TimeUnit unit,
 ScheduledExecutorService executor,
 Flow.Publisher<T> fallback)

Switches to a fallback single if the upstream doesn't signal the next item, error or completion within the specified time.

Parameters:

timeout - the time to wait for the upstream to signal

unit - the time unit

executor - the executor to use for waiting for the upstream signal

fallback - the Single to switch to if the upstream doesn't signal in time

Returns:

Multi

Throws:

NullPointerException - if unit, executor or fallback is null

to

default <U> U to(Function<? super Multi<T>,? extends U> converter)

Apply the given converter function to the current Multi instance and return the value returned by this function.

Note that the converter function is executed upon calling this method immediately and not when the resulting sequence gets subscribed to.

Type Parameters:

U - the output type

Parameters:

converter - the function that receives the current Multi instance and should return a value to be returned by the method

Returns:

the value returned by the function

Throws:

NullPointerException - if converter is null

forEach

default Single<Void> forEach(Consumer<? super T> consumer)

Terminal stage, invokes provided consumer for every item in the stream with no backpressure.

Parameters:

consumer - consumer to be invoked for each item

Returns:

Single completed when the stream terminates

forEachCompletionStage

default Single<Void> forEachCompletionStage(Function<? super T,CompletionStage<Void>> function)

Terminal stage, invokes provided consumer for every item in the stream with strict backpressure. Items are requested 1 by 1 with no prefetch always waiting for each completion stage to complete before requesting another item.

Parameters:

function - invoked for each item returning completion stage to signal asynchronous completion

Returns:

Single completed when the stream terminates

ignoreElements

default Single<Void> ignoreElements()

Terminal stage, ignore all items and complete returned Single<Void> successfully or exceptionally.

Returns:

Single completed when the stream terminates