SubFlow

java.lang.Object
- akka.stream.javadsl.SubFlow<In,Out,Mat>

```
public class SubFlow<In,Out,Mat>
extends java.lang.Object
```
A “stream of streams” sub-flow of data elements, e.g. produced by groupBy. SubFlows cannot contribute to the super-flow’s materialized value since they are materialized later, during the runtime of the flow graph processing.

Constructor Summary

Constructors
Constructor and Description

SubFlow(SubFlow<Out,Mat,Flow<In,java.lang.Object,Mat>,Sink<In,Mat>> delegate)

Constructors
Constructor and Description
`SubFlow(SubFlow<Out,Mat,Flow<In,java.lang.Object,Mat>,Sink<In,Mat>> delegate)`

Method Summary

All Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`SubFlow<In,Out,Mat>`	`addAttributes(Attributes attr)` Add the given attributes to this Source.
`SubFlow<In,Out,Mat>`	`alsoTo(Graph<SinkShape<Out>,?> that)` Attaches the given `Sink` to this `Flow`, meaning that elements that passes through will also be sent to the `Sink`.
`SubFlow<Out,Mat,Flow<In,java.lang.Object,Mat>,Sink<In,Mat>>`	`asScala()` Converts this Flow to its Scala DSL counterpart
`SubFlow<In,Out,Mat>`	`async()` Put an asynchronous boundary around this `SubFlow`
`SubFlow<In,Out,Mat>`	`backpressureTimeout(scala.concurrent.duration.FiniteDuration timeout)` If the time between the emission of an element and the following downstream demand exceeds the provided timeout, the stream is failed with a `TimeoutException`.
`<S> SubFlow<In,S,Mat>`	`batch(long max, Function<Out,S> seed, Function2<S,Out,S> aggregate)` Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches until the subscriber is ready to accept them.
`<S> SubFlow<In,S,Mat>`	`batchWeighted(long max, Function<Out,java.lang.Object> costFn, Function<Out,S> seed, Function2<S,Out,S> aggregate)` Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches until the subscriber is ready to accept them.
`SubFlow<In,Out,Mat>`	`buffer(int size, OverflowStrategy overflowStrategy)` Adds a fixed size buffer in the flow that allows to store elements from a faster upstream until it becomes full.
`<T> SubFlow<In,T,Mat>`	`collect(scala.PartialFunction<Out,T> pf)` Transform this stream by applying the given partial function to each of the elements on which the function is defined as they pass through this processing step.
`SubFlow<In,Out,Mat>`	`completionTimeout(scala.concurrent.duration.FiniteDuration timeout)` If the completion of the stream does not happen until the provided timeout, the stream is failed with a `TimeoutException`.
`<T,M> SubFlow<In,T,Mat>`	`concat(Graph<SourceShape<T>,M> that)` Concatenate the given `Source` to this `Flow`, meaning that once this Flow’s input is exhausted and all result elements have been generated, the Source’s elements will be produced.
`Flow<In,Out,Mat>`	`concatSubstreams()` Flatten the sub-flows back into the super-flow by concatenating them.
`<O2> SubFlow<In,O2,Mat>`	`conflate(Function2<O2,O2,O2> aggregate)` Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary until the subscriber is ready to accept them.
`<S> SubFlow<In,S,Mat>`	`conflateWithSeed(Function<Out,S> seed, Function2<S,Out,S> aggregate)` Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary until the subscriber is ready to accept them.
`SubFlow<In,Out,Mat>`	`delay(scala.concurrent.duration.FiniteDuration of, DelayOverflowStrategy strategy)` Shifts elements emission in time by a specified amount.
`SubFlow<In,Out,Mat>`	`detach()` Detaches upstream demand from downstream demand without detaching the stream rates; in other words acts like a buffer of size 1.
`SubFlow<In,Out,Mat>`	`drop(long n)` Discard the given number of elements at the beginning of the stream.
`SubFlow<In,Out,Mat>`	`dropWhile(Predicate<Out> p)` Discard elements at the beginning of the stream while predicate is true.
`SubFlow<In,Out,Mat>`	`dropWithin(scala.concurrent.duration.FiniteDuration d)` Discard the elements received within the given duration at beginning of the stream.
`<U> SubFlow<In,U,Mat>`	`expand(Function<Out,java.util.Iterator<U>> extrapolate)` Allows a faster downstream to progress independently of a slower publisher by extrapolating elements from an older element until new element comes from the upstream.
`SubFlow<In,Out,Mat>`	`filter(Predicate<Out> p)` Only pass on those elements that satisfy the given predicate.
`SubFlow<In,Out,Mat>`	`filterNot(Predicate<Out> p)` Only pass on those elements that NOT satisfy the given predicate.
`<T,M> SubFlow<In,T,Mat>`	`flatMapConcat(Function<Out,? extends Graph<SourceShape<T>,M>> f)` Transform each input element into a `Source` of output elements that is then flattened into the output stream by concatenation, fully consuming one Source after the other.
`<T,M> SubFlow<In,T,Mat>`	`flatMapMerge(int breadth, Function<Out,? extends Graph<SourceShape<T>,M>> f)` Transform each input element into a `Source` of output elements that is then flattened into the output stream by merging, where at most `breadth` substreams are being consumed at any given time.
`<T> SubFlow<In,T,Mat>`	`fold(T zero, Function2<T,Out,T> f)` Similar to `scan` but only emits its result when the upstream completes, after which it also completes.
`<T> SubFlow<In,T,Mat>`	`foldAsync(T zero, Function2<T,Out,java.util.concurrent.CompletionStage<T>> f)` Similar to `fold` but with an asynchronous function.
`SubFlow<In,java.util.List<Out>,Mat>`	`grouped(int n)` Chunk up this stream into groups of the given size, with the last group possibly smaller than requested due to end-of-stream.
`SubFlow<In,java.util.List<Out>,Mat>`	`groupedWithin(int n, scala.concurrent.duration.FiniteDuration d)` Chunk up this stream into groups of elements received within a time window, or limited by the given number of elements, whatever happens first.
`SubFlow<In,Out,Mat>`	`idleTimeout(scala.concurrent.duration.FiniteDuration timeout)` If the time between two processed elements exceeds the provided timeout, the stream is failed with a `TimeoutException`.
`SubFlow<In,Out,Mat>`	`initialDelay(scala.concurrent.duration.FiniteDuration delay)` Delays the initial element by the specified duration.
`SubFlow<In,Out,Mat>`	`initialTimeout(scala.concurrent.duration.FiniteDuration timeout)` If the first element has not passed through this stage before the provided timeout, the stream is failed with a `TimeoutException`.
`<T> SubFlow<In,T,Mat>`	`interleave(Graph<SourceShape<T>,?> that, int segmentSize)` Interleave is a deterministic merge of the given `Source` with elements of this `Flow`.
`<T> SubFlow<In,T,Mat>`	`intersperse(T inject)` Intersperses stream with provided element, similar to how `scala.collection.immutable.List.mkString` injects a separator between a List's elements.
`<T> SubFlow<In,T,Mat>`	`intersperse(T start, T inject, T end)` Intersperses stream with provided element, similar to how `scala.collection.immutable.List.mkString` injects a separator between a List's elements.
`<U> SubFlow<In,U,Mat>`	`keepAlive(scala.concurrent.duration.FiniteDuration maxIdle, Creator<U> injectedElem)` Injects additional elements if upstream does not emit for a configured amount of time.
`SubFlow<In,Out,Mat>`	`limit(long n)` Ensure stream boundedness by limiting the number of elements from upstream.
`SubFlow<In,Out,Mat>`	`limitWeighted(long n, Function<Out,java.lang.Object> costFn)` Ensure stream boundedness by evaluating the cost of incoming elements using a cost function.
`SubFlow<In,Out,Mat>`	`log(java.lang.String name)` Logs elements flowing through the stream as well as completion and erroring.
`SubFlow<In,Out,Mat>`	`log(java.lang.String name, Function<Out,java.lang.Object> extract)` Logs elements flowing through the stream as well as completion and erroring.
`SubFlow<In,Out,Mat>`	`log(java.lang.String name, Function<Out,java.lang.Object> extract, LoggingAdapter log)` Logs elements flowing through the stream as well as completion and erroring.
`SubFlow<In,Out,Mat>`	`log(java.lang.String name, LoggingAdapter log)` Logs elements flowing through the stream as well as completion and erroring.
`<T> SubFlow<In,T,Mat>`	`map(Function<Out,T> f)` Transform this stream by applying the given function to each of the elements as they pass through this processing step.
`<T> SubFlow<In,T,Mat>`	`mapAsync(int parallelism, Function<Out,java.util.concurrent.CompletionStage<T>> f)` Transform this stream by applying the given function to each of the elements as they pass through this processing step.
`<T> SubFlow<In,T,Mat>`	`mapAsyncUnordered(int parallelism, Function<Out,java.util.concurrent.CompletionStage<T>> f)` Transform this stream by applying the given function to each of the elements as they pass through this processing step.
`<T> SubFlow<In,T,Mat>`	`mapConcat(Function<Out,java.lang.Iterable<T>> f)` Transform each input element into an `Iterable` of output elements that is then flattened into the output stream.
`SubFlow<In,Out,Mat>`	`mapError(scala.PartialFunction<java.lang.Throwable,java.lang.Throwable> pf)` While similar to `recover` this stage can be used to transform an error signal to a different one without logging it as an error in the process.
`<T> SubFlow<In,T,Mat>`	`merge(Graph<SourceShape<T>,?> that)` Merge the given `Source` to this `Flow`, taking elements as they arrive from input streams, picking randomly when several elements ready.
`<U,M> SubFlow<In,U,Mat>`	`mergeSorted(Graph<SourceShape<U>,M> that, java.util.Comparator<U> comp)` Merge the given `Source` to this `Flow`, taking elements as they arrive from input streams, picking always the smallest of the available elements (waiting for one element from each side to be available).
`Flow<In,Out,Mat>`	`mergeSubstreams()` Flatten the sub-flows back into the super-flow by performing a merge without parallelism limit (i.e.
`Flow<In,Out,Mat>`	`mergeSubstreamsWithParallelism(int parallelism)` Flatten the sub-flows back into the super-flow by performing a merge with the given parallelism limit.
`SubFlow<In,Out,Mat>`	`named(java.lang.String name)` Add a name attribute to this Flow.
`<T,M> SubFlow<In,T,Mat>`	`orElse(Graph<SourceShape<T>,M> secondary)` Provides a secondary source that will be consumed if this source completes without any elements passing by.
`SubFlow<In,Pair<java.util.List<Out>,Source<Out,NotUsed>>,Mat>`	`prefixAndTail(int n)` Takes up to `n` elements from the stream (less than `n` only if the upstream completes before emitting `n` elements) and returns a pair containing a strict sequence of the taken element and a stream representing the remaining elements.
`<T,M> SubFlow<In,T,Mat>`	`prepend(Graph<SourceShape<T>,M> that)` Prepend the given `Source` to this `Flow`, meaning that before elements are generated from this Flow, the Source's elements will be produced until it is exhausted, at which point Flow elements will start being produced.
`<T> SubFlow<In,T,Mat>`	`recover(scala.PartialFunction<java.lang.Throwable,T> pf)` Recover allows to send last element on failure and gracefully complete the stream Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements.
`<T> SubFlow<In,T,Mat>`	`recoverWith(scala.PartialFunction<java.lang.Throwable,? extends Graph<SourceShape<T>,NotUsed>> pf)` Deprecated. Use recoverWithRetries instead. Since 2.4.4.
`<T> SubFlow<In,T,Mat>`	`recoverWithRetries(int attempts, scala.PartialFunction<java.lang.Throwable,? extends Graph<SourceShape<T>,NotUsed>> pf)` RecoverWithRetries allows to switch to alternative Source on flow failure.
`SubFlow<In,Out,Mat>`	`reduce(Function2<Out,Out,Out> f)` Similar to `fold` but uses first element as zero element.
`<T> SubFlow<In,T,Mat>`	`scan(T zero, Function2<T,Out,T> f)` Similar to `fold` but is not a terminal operation, emits its current value which starts at `zero` and then applies the current and next value to the given function `f`, emitting the next current value.
`<T> SubFlow<In,T,Mat>`	`scanAsync(T zero, Function2<T,Out,java.util.concurrent.CompletionStage<T>> f)` Similar to `scan` but with a asynchronous function, emits its current value which starts at `zero` and then applies the current and next value to the given function `f`, emitting a `Future` that resolves to the next current value.
`SubFlow<In,java.util.List<Out>,Mat>`	`sliding(int n, int step)` Apply a sliding window over the stream and return the windows as groups of elements, with the last group possibly smaller than requested due to end-of-stream.
`<T> SubFlow<In,T,Mat>`	`statefulMapConcat(Creator<Function<Out,java.lang.Iterable<T>>> f)` Transform each input element into an `Iterable` of output elements that is then flattened into the output stream.
`SubFlow<In,Out,Mat>`	`take(long n)` Terminate processing (and cancel the upstream publisher) after the given number of elements.
`SubFlow<In,Out,Mat>`	`takeWhile(Predicate<Out> p)` Terminate processing (and cancel the upstream publisher) after predicate returns false for the first time, Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
`SubFlow<In,Out,Mat>`	`takeWhile(Predicate<Out> p, boolean inclusive)` Terminate processing (and cancel the upstream publisher) after predicate returns false for the first time, including the first failed element iff inclusive is true Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
`SubFlow<In,Out,Mat>`	`takeWithin(scala.concurrent.duration.FiniteDuration d)` Terminate processing (and cancel the upstream publisher) after the given duration.
`SubFlow<In,Out,Mat>`	`throttle(int cost, scala.concurrent.duration.FiniteDuration per, int maximumBurst, Function<Out,java.lang.Integer> costCalculation, ThrottleMode mode)` Sends elements downstream with speed limited to `cost/per`.
`SubFlow<In,Out,Mat>`	`throttle(int elements, scala.concurrent.duration.FiniteDuration per, int maximumBurst, ThrottleMode mode)` Sends elements downstream with speed limited to `elements/per`.
`Sink<In,Mat>`	`to(Graph<SinkShape<Out>,?> sink)` Connect this `SubFlow` to a `Sink`, concatenating the processing steps of both.
`<U> SubFlow<In,U,Mat>`	`transform(Creator<Stage<Out,U>> mkStage)` Deprecated. Use via(GraphStage) instead. Since 2.4.3.
`<T,M> SubFlow<In,T,Mat>`	`via(Graph<FlowShape<Out,T>,M> flow)` Transform this `Flow` by appending the given processing steps.
`SubFlow<In,Out,Mat>`	`withAttributes(Attributes attr)` Change the attributes of this `Source` to the given ones and seal the list of attributes.
`<T> SubFlow<In,scala.Tuple2<Out,T>,Mat>`	`zip(Graph<SourceShape<T>,?> source)` Combine the elements of current `Flow` and the given `Source` into a stream of tuples.
`<Out2,Out3> SubFlow<In,Out3,Mat>`	`zipWith(Graph<SourceShape<Out2>,?> that, Function2<Out,Out2,Out3> combine)` Put together the elements of current `Flow` and the given `Source` into a stream of combined elements using a combiner function.
`SubFlow<In,Pair<Out,java.lang.Object>,Mat>`	`zipWithIndex()` Combine the elements of current `Flow` into a stream of tuples consisting of all elements paired with their index.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
 - SubFlow
```
public SubFlow(SubFlow<Out,Mat,Flow<In,java.lang.Object,Mat>,Sink<In,Mat>> delegate)
```
- Method Detail
 - asScala
```
public SubFlow<Out,Mat,Flow<In,java.lang.Object,Mat>,Sink<In,Mat>> asScala()
```
 Converts this Flow to its Scala DSL counterpart
 - mergeSubstreams
```
public Flow<In,Out,Mat> mergeSubstreams()
```
 Flatten the sub-flows back into the super-flow by performing a merge without parallelism limit (i.e. having an unbounded number of sub-flows active concurrently).
 This is identical in effect to mergeSubstreamsWithParallelism(Integer.MAX_VALUE).
 
 Returns:
 
 (undocumented)
 - mergeSubstreamsWithParallelism
```
public Flow<In,Out,Mat> mergeSubstreamsWithParallelism(int parallelism)
```
 Flatten the sub-flows back into the super-flow by performing a merge with the given parallelism limit. This means that only up to parallelism substreams will be executed at any given time. Substreams that are not yet executed are also not materialized, meaning that back-pressure will be exerted at the operator that creates the substreams when the parallelism limit is reached.
 
 Parameters:
 
 parallelism - (undocumented)
 
 Returns:
 
 (undocumented)
 - concatSubstreams
```
public Flow<In,Out,Mat> concatSubstreams()
```
 Flatten the sub-flows back into the super-flow by concatenating them. This is usually a bad idea when combined with groupBy since it can easily lead to deadlock—the concatenation does not consume from the second substream until the first has finished and the groupBy stage will get back-pressure from the second stream.
 This is identical in effect to mergeSubstreamsWithParallelism(1).
 
 Returns:
 
 (undocumented)
 - via
```
public <T,M> SubFlow<In,T,Mat> via(Graph<FlowShape<Out,T>,M> flow)
```
 Transform this Flow by appending the given processing steps.
```
 +----------------------------+
 | Resulting Flow |
 | |
 | +------+ +------+ |
 | | | | | |
 In ~~> | this | ~Out~> | flow | ~~> T
 | | | | | |
 | +------+ +------+ |
 +----------------------------+
 
```
 The materialized value of the combined Flow will be the materialized value of the current flow (ignoring the other Flow’s value), use viaMat if a different strategy is needed.
 Parameters:
 
 flow - (undocumented)
 
 Returns:
 
 (undocumented)
 - to
```
public Sink<In,Mat> to(Graph<SinkShape<Out>,?> sink)
```
 Connect this SubFlow to a Sink, concatenating the processing steps of both. This means that all sub-flows that result from the previous sub-stream operator will be attached to the given sink.
```
 +----------------------------+
 | Resulting Sink |
 | |
 | +------+ +------+ |
 | | | | | |
 In ~~> | flow | ~Out~> | sink | |
 | | | | | |
 | +------+ +------+ |
 +----------------------------+
 
```
 Parameters:
 
 sink - (undocumented)
 
 Returns:
 
 (undocumented)
 - map
```
public <T> SubFlow<In,T,Mat> map(Function<Out,T> f)
```
 Transform this stream by applying the given function to each of the elements as they pass through this processing step.
 '''Emits when''' the mapping function returns an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - mapConcat
```
public <T> SubFlow<In,T,Mat> mapConcat(Function<Out,java.lang.Iterable<T>> f)
```
 Transform each input element into an Iterable of output elements that is then flattened into the output stream.
 Make sure that the Iterable is immutable or at least not modified after being used as an output sequence. Otherwise the stream may fail with ConcurrentModificationException or other more subtle errors may occur.
 The returned Iterable MUST NOT contain null values, as they are illegal as stream elements - according to the Reactive Streams specification.
 '''Emits when''' the mapping function returns an element or there are still remaining elements from the previously calculated collection
 '''Backpressures when''' downstream backpressures or there are still remaining elements from the previously calculated collection
 '''Completes when''' upstream completes and all remaining elements has been emitted
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - statefulMapConcat
```
public <T> SubFlow<In,T,Mat> statefulMapConcat(Creator<Function<Out,java.lang.Iterable<T>>> f)
```
 Transform each input element into an Iterable of output elements that is then flattened into the output stream. The transformation is meant to be stateful, which is enabled by creating the transformation function anew for every materialization — the returned function will typically close over mutable objects to store state between invocations. For the stateless variant see mapConcat(akka.japi.function.Function<Out, java.lang.Iterable<T>>).
 Make sure that the Iterable is immutable or at least not modified after being used as an output sequence. Otherwise the stream may fail with ConcurrentModificationException or other more subtle errors may occur.
 The returned Iterable MUST NOT contain null values, as they are illegal as stream elements - according to the Reactive Streams specification.
 '''Emits when''' the mapping function returns an element or there are still remaining elements from the previously calculated collection
 '''Backpressures when''' downstream backpressures or there are still remaining elements from the previously calculated collection
 '''Completes when''' upstream completes and all remaining elements has been emitted
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - mapAsync
```
public <T> SubFlow<In,T,Mat> mapAsync(int parallelism,
 Function<Out,java.util.concurrent.CompletionStage<T>> f)
```
 Transform this stream by applying the given function to each of the elements as they pass through this processing step. The function returns a CompletionStage and the value of that future will be emitted downstream. The number of CompletionStages that shall run in parallel is given as the first argument to mapAsync. These CompletionStages may complete in any order, but the elements that are emitted downstream are in the same order as received from upstream.
 If the function f throws an exception or if the CompletionStage is completed with failure and the supervision decision is Supervision.stop() the stream will be completed with failure.
 If the function f throws an exception or if the CompletionStage is completed with failure and the supervision decision is Supervision.resume() or Supervision.restart() the element is dropped and the stream continues.
 The function f is always invoked on the elements in the order they arrive.
 '''Emits when''' the CompletionStage returned by the provided function finishes for the next element in sequence
 '''Backpressures when''' the number of CompletionStages reaches the configured parallelism and the downstream backpressures or the first CompletionStage is not completed
 '''Completes when''' upstream completes and all CompletionStages has been completed and all elements has been emitted
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 parallelism - (undocumented)
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 
 See Also:
 
 mapAsyncUnordered(int, akka.japi.function.Function<Out, java.util.concurrent.CompletionStage<T>>)
 - mapAsyncUnordered
```
public <T> SubFlow<In,T,Mat> mapAsyncUnordered(int parallelism,
 Function<Out,java.util.concurrent.CompletionStage<T>> f)
```
 Transform this stream by applying the given function to each of the elements as they pass through this processing step. The function returns a CompletionStage and the value of that future will be emitted downstream. The number of CompletionStages that shall run in parallel is given as the first argument to mapAsyncUnordered. Each processed element will be emitted downstream as soon as it is ready, i.e. it is possible that the elements are not emitted downstream in the same order as received from upstream.
 If the function f throws an exception or if the CompletionStage is completed with failure and the supervision decision is Supervision.stop() the stream will be completed with failure.
 If the function f throws an exception or if the CompletionStage is completed with failure and the supervision decision is Supervision.resume() or Supervision.restart() the element is dropped and the stream continues.
 The function f is always invoked on the elements in the order they arrive (even though the result of the CompletionStages returned by f might be emitted in a different order).
 '''Emits when''' any of the CompletionStages returned by the provided function complete
 '''Backpressures when''' the number of CompletionStages reaches the configured parallelism and the downstream backpressures
 '''Completes when''' upstream completes and all CompletionStages have been completed and all elements has been emitted
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 parallelism - (undocumented)
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 
 See Also:
 
 mapAsync(int, akka.japi.function.Function<Out, java.util.concurrent.CompletionStage<T>>)
 - filter
```
public SubFlow<In,Out,Mat> filter(Predicate<Out> p)
```
 Only pass on those elements that satisfy the given predicate.
 '''Emits when''' the given predicate returns true for the element
 '''Backpressures when''' the given predicate returns true for the element and downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 p - (undocumented)
 
 Returns:
 
 (undocumented)
 - filterNot
```
public SubFlow<In,Out,Mat> filterNot(Predicate<Out> p)
```
 Only pass on those elements that NOT satisfy the given predicate.
 '''Emits when''' the given predicate returns false for the element
 '''Backpressures when''' the given predicate returns false for the element and downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 p - (undocumented)
 
 Returns:
 
 (undocumented)
 - collect
```
public <T> SubFlow<In,T,Mat> collect(scala.PartialFunction<Out,T> pf)
```
 Transform this stream by applying the given partial function to each of the elements on which the function is defined as they pass through this processing step. Non-matching elements are filtered out.
 '''Emits when''' the provided partial function is defined for the element
 '''Backpressures when''' the partial function is defined for the element and downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 pf - (undocumented)
 
 Returns:
 
 (undocumented)
 - grouped
```
public SubFlow<In,java.util.List<Out>,Mat> grouped(int n)
```
 Chunk up this stream into groups of the given size, with the last group possibly smaller than requested due to end-of-stream.
 n must be positive, otherwise IllegalArgumentException is thrown.
 '''Emits when''' the specified number of elements has been accumulated or upstream completed
 '''Backpressures when''' a group has been assembled and downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 n - (undocumented)
 
 Returns:
 
 (undocumented)
 - limit
```
public SubFlow<In,Out,Mat> limit(long n)
```
 Ensure stream boundedness by limiting the number of elements from upstream. If the number of incoming elements exceeds max, it will signal upstream failure StreamLimitException downstream.
 Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
 The stream will be completed without producing any elements if n is zero or negative.
 '''Emits when''' the specified number of elements to take has not yet been reached
 '''Backpressures when''' downstream backpressures
 '''Completes when''' the defined number of elements has been taken or upstream completes
 '''Cancels when''' the defined number of elements has been taken or downstream cancels
 See also Flow.take, Flow.takeWithin, Flow.takeWhile
 
 Parameters:
 
 n - (undocumented)
 
 Returns:
 
 (undocumented)
 - limitWeighted
```
public SubFlow<In,Out,Mat> limitWeighted(long n,
 Function<Out,java.lang.Object> costFn)
```
 Ensure stream boundedness by evaluating the cost of incoming elements using a cost function. Exactly how many elements will be allowed to travel downstream depends on the evaluated cost of each element. If the accumulated cost exceeds max, it will signal upstream failure StreamLimitException downstream.
 Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
 The stream will be completed without producing any elements if n is zero or negative.
 '''Emits when''' the specified number of elements to take has not yet been reached
 '''Backpressures when''' downstream backpressures
 '''Completes when''' the defined number of elements has been taken or upstream completes
 '''Cancels when''' the defined number of elements has been taken or downstream cancels
 See also Flow.take, Flow.takeWithin, Flow.takeWhile
 
 Parameters:
 
 n - (undocumented)
 
 costFn - (undocumented)
 
 Returns:
 
 (undocumented)
 - sliding
```
public SubFlow<In,java.util.List<Out>,Mat> sliding(int n,
 int step)
```
 Apply a sliding window over the stream and return the windows as groups of elements, with the last group possibly smaller than requested due to end-of-stream.
 n must be positive, otherwise IllegalArgumentException is thrown. step must be positive, otherwise IllegalArgumentException is thrown.
 '''Emits when''' enough elements have been collected within the window or upstream completed
 '''Backpressures when''' a window has been assembled and downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 n - (undocumented)
 
 step - (undocumented)
 
 Returns:
 
 (undocumented)
 - scan
```
public <T> SubFlow<In,T,Mat> scan(T zero,
 Function2<T,Out,T> f)
```
 Similar to fold but is not a terminal operation, emits its current value which starts at zero and then applies the current and next value to the given function f, emitting the next current value.
 If the function f throws an exception and the supervision decision is Supervision.restart() current value starts at zero again the stream will continue.
 '''Emits when''' the function scanning the element returns a new element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 zero - (undocumented)
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - scanAsync
```
public <T> SubFlow<In,T,Mat> scanAsync(T zero,
 Function2<T,Out,java.util.concurrent.CompletionStage<T>> f)
```
 Similar to scan but with a asynchronous function, emits its current value which starts at zero and then applies the current and next value to the given function f, emitting a Future that resolves to the next current value.
 If the function f throws an exception and the supervision decision is akka.stream.Supervision.Restart current value starts at zero again the stream will continue.
 If the function f throws an exception and the supervision decision is akka.stream.Supervision.Resume current value starts at the previous current value, or zero when it doesn't have one, and the stream will continue.
 '''Emits when''' the future returned by f completes
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes and the last future returned by f completes
 '''Cancels when''' downstream cancels
 See also FlowOps.scan
 
 Parameters:
 
 zero - (undocumented)
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - fold
```
public <T> SubFlow<In,T,Mat> fold(T zero,
 Function2<T,Out,T> f)
```
 Similar to scan but only emits its result when the upstream completes, after which it also completes. Applies the given function f towards its current and next value, yielding the next current value.
 If the function f throws an exception and the supervision decision is Supervision.restart() current value starts at zero again the stream will continue.
 '''Emits when''' upstream completes
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 zero - (undocumented)
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - foldAsync
```
public <T> SubFlow<In,T,Mat> foldAsync(T zero,
 Function2<T,Out,java.util.concurrent.CompletionStage<T>> f)
```
 Similar to fold but with an asynchronous function. Applies the given function towards its current and next value, yielding the next current value.
 If the function f returns a failure and the supervision decision is akka.stream.Supervision.Restart current value starts at zero again the stream will continue.
 '''Emits when''' upstream completes
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 zero - (undocumented)
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - reduce
```
public SubFlow<In,Out,Mat> reduce(Function2<Out,Out,Out> f)
```
 Similar to fold but uses first element as zero element. Applies the given function towards its current and next value, yielding the next current value.
 '''Emits when''' upstream completes
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - intersperse
```
public <T> SubFlow<In,T,Mat> intersperse(T start,
 T inject,
 T end)
```
 Intersperses stream with provided element, similar to how scala.collection.immutable.List.mkString injects a separator between a List's elements.
 Additionally can inject start and end marker elements to stream.
 Examples:
```
 Source<Integer, ?> nums = Source.from(Arrays.asList(0, 1, 2, 3));
 nums.intersperse(","); // 1 , 2 , 3
 nums.intersperse("[", ",", "]"); // [ 1 , 2 , 3 ]
 
```
 In case you want to only prepend or only append an element (yet still use the intercept feature to inject a separator between elements, you may want to use the following pattern instead of the 3-argument version of intersperse (See Source.concat for semantics details):
```
 Source.single(">> ").concat(flow.intersperse(","))
 flow.intersperse(",").concat(Source.single("END"))
 
```
 '''Emits when''' upstream emits (or before with the start element if provided)
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 Parameters:
 
 start - (undocumented)
 
 inject - (undocumented)
 
 end - (undocumented)
 
 Returns:
 
 (undocumented)
 - intersperse
```
public <T> SubFlow<In,T,Mat> intersperse(T inject)
```
 Intersperses stream with provided element, similar to how scala.collection.immutable.List.mkString injects a separator between a List's elements.
 Additionally can inject start and end marker elements to stream.
 Examples:
```
 Source<Integer, ?> nums = Source.from(Arrays.asList(0, 1, 2, 3));
 nums.intersperse(","); // 1 , 2 , 3
 nums.intersperse("[", ",", "]"); // [ 1 , 2 , 3 ]
 
```
 '''Emits when''' upstream emits (or before with the start element if provided)
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 Parameters:
 
 inject - (undocumented)
 
 Returns:
 
 (undocumented)
 - groupedWithin
```
public SubFlow<In,java.util.List<Out>,Mat> groupedWithin(int n,
 scala.concurrent.duration.FiniteDuration d)
```
 Chunk up this stream into groups of elements received within a time window, or limited by the given number of elements, whatever happens first. Empty groups will not be emitted if no elements are received from upstream. The last group before end-of-stream will contain the buffered elements since the previously emitted group.
 '''Emits when''' the configured time elapses since the last group has been emitted
 '''Backpressures when''' the configured time elapses since the last group has been emitted
 '''Completes when''' upstream completes (emits last group)
 '''Cancels when''' downstream completes
 n must be positive, and d must be greater than 0 seconds, otherwise IllegalArgumentException is thrown.
 
 Parameters:
 
 n - (undocumented)
 
 d - (undocumented)
 
 Returns:
 
 (undocumented)
 - delay
```
public SubFlow<In,Out,Mat> delay(scala.concurrent.duration.FiniteDuration of,
 DelayOverflowStrategy strategy)
```
 Shifts elements emission in time by a specified amount. It allows to store elements in internal buffer while waiting for next element to be emitted. Depending on the defined DelayOverflowStrategy it might drop elements or backpressure the upstream if there is no space available in the buffer.
 Delay precision is 10ms to avoid unnecessary timer scheduling cycles
 Internal buffer has default capacity 16. You can set buffer size by calling withAttributes(inputBuffer)
 '''Emits when''' there is a pending element in the buffer and configured time for this element elapsed * EmitEarly - strategy do not wait to emit element if buffer is full
 '''Backpressures when''' depending on OverflowStrategy * Backpressure - backpressures when buffer is full * DropHead, DropTail, DropBuffer - never backpressures * Fail - fails the stream if buffer gets full
 '''Completes when''' upstream completes and buffered elements has been drained
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 of - time to shift all messages
 
 strategy - Strategy that is used when incoming elements cannot fit inside the buffer
 
 Returns:
 
 (undocumented)
 - drop
```
public SubFlow<In,Out,Mat> drop(long n)
```
 Discard the given number of elements at the beginning of the stream. No elements will be dropped if n is zero or negative.
 '''Emits when''' the specified number of elements has been dropped already
 '''Backpressures when''' the specified number of elements has been dropped and downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 n - (undocumented)
 
 Returns:
 
 (undocumented)
 - dropWithin
```
public SubFlow<In,Out,Mat> dropWithin(scala.concurrent.duration.FiniteDuration d)
```
 Discard the elements received within the given duration at beginning of the stream.
 '''Emits when''' the specified time elapsed and a new upstream element arrives
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 d - (undocumented)
 
 Returns:
 
 (undocumented)
 - takeWhile
```
public SubFlow<In,Out,Mat> takeWhile(Predicate<Out> p)
```
 Terminate processing (and cancel the upstream publisher) after predicate returns false for the first time, Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
 The stream will be completed without producing any elements if predicate is false for the first stream element.
 '''Emits when''' the predicate is true
 '''Backpressures when''' downstream backpressures
 '''Completes when''' predicate returned false (or 1 after predicate returns false if inclusive or upstream completes
 '''Cancels when''' predicate returned false or downstream cancels
 
 Parameters:
 
 p - (undocumented)
 
 Returns:
 
 (undocumented)
 - takeWhile
```
public SubFlow<In,Out,Mat> takeWhile(Predicate<Out> p,
 boolean inclusive)
```
 Terminate processing (and cancel the upstream publisher) after predicate returns false for the first time, including the first failed element iff inclusive is true Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
 The stream will be completed without producing any elements if predicate is false for the first stream element.
 '''Emits when''' the predicate is true
 '''Backpressures when''' downstream backpressures
 '''Completes when''' predicate returned false (or 1 after predicate returns false if inclusive or upstream completes
 '''Cancels when''' predicate returned false or downstream cancels
 
 Parameters:
 
 p - (undocumented)
 
 inclusive - (undocumented)
 
 Returns:
 
 (undocumented)
 - dropWhile
```
public SubFlow<In,Out,Mat> dropWhile(Predicate<Out> p)
```
 Discard elements at the beginning of the stream while predicate is true. All elements will be taken after predicate returns false first time.
 '''Emits when''' predicate returned false and for all following stream elements
 '''Backpressures when''' predicate returned false and downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 p - (undocumented)
 
 Returns:
 
 (undocumented)
 - recover
```
public <T> SubFlow<In,T,Mat> recover(scala.PartialFunction<java.lang.Throwable,T> pf)
```
 Recover allows to send last element on failure and gracefully complete the stream Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This stage can recover the failure signal, but not the skipped elements, which will be dropped.
 Throwing an exception inside recover _will_ be logged on ERROR level automatically.
 '''Emits when''' element is available from the upstream or upstream is failed and pf returns an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or upstream failed with exception pf can handle
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 pf - (undocumented)
 
 Returns:
 
 (undocumented)
 - recoverWith
```
public <T> SubFlow<In,T,Mat> recoverWith(scala.PartialFunction<java.lang.Throwable,? extends Graph<SourceShape<T>,NotUsed>> pf)
```
 Deprecated. Use recoverWithRetries instead. Since 2.4.4.
 
 RecoverWith allows to switch to alternative Source on flow failure. It will stay in effect after a failure has been recovered so that each time there is a failure it is fed into the pf and a new Source may be materialized.
 Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This stage can recover the failure signal, but not the skipped elements, which will be dropped.
 Throwing an exception inside recoverWith _will_ be logged on ERROR level automatically.
 '''Emits when''' element is available from the upstream or upstream is failed and element is available from alternative Source
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or upstream failed with exception pf can handle
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 pf - (undocumented)
 
 Returns:
 
 (undocumented)
 - recoverWithRetries
```
public <T> SubFlow<In,T,Mat> recoverWithRetries(int attempts,
 scala.PartialFunction<java.lang.Throwable,? extends Graph<SourceShape<T>,NotUsed>> pf)
```
 RecoverWithRetries allows to switch to alternative Source on flow failure. It will stay in effect after a failure has been recovered up to attempts number of times so that each time there is a failure it is fed into the pf and a new Source may be materialized. Note that if you pass in 0, this won't attempt to recover at all. Passing in a negative number will behave exactly the same as recoverWith.
 Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This stage can recover the failure signal, but not the skipped elements, which will be dropped.
 Throwing an exception inside recoverWithRetries _will_ be logged on ERROR level automatically.
 '''Emits when''' element is available from the upstream or upstream is failed and element is available from alternative Source
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or upstream failed with exception pf can handle
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 attempts - (undocumented)
 
 pf - (undocumented)
 
 Returns:
 
 (undocumented)
 - mapError
```
public SubFlow<In,Out,Mat> mapError(scala.PartialFunction<java.lang.Throwable,java.lang.Throwable> pf)
```
 While similar to recover this stage can be used to transform an error signal to a different one *without* logging it as an error in the process. So in that sense it is NOT exactly equivalent to recover(t => throw t2) since recover would log the t2 error.
 Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This stage can recover the failure signal, but not the skipped elements, which will be dropped.
 Similarily to recover throwing an exception inside mapError _will_ be logged.
 '''Emits when''' element is available from the upstream or upstream is failed and pf returns an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or upstream failed with exception pf can handle
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 pf - (undocumented)
 
 Returns:
 
 (undocumented)
 - take
```
public SubFlow<In,Out,Mat> take(long n)
```
 Terminate processing (and cancel the upstream publisher) after the given number of elements. Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
 The stream will be completed without producing any elements if n is zero or negative.
 '''Emits when''' the specified number of elements to take has not yet been reached
 '''Backpressures when''' downstream backpressures
 '''Completes when''' the defined number of elements has been taken or upstream completes
 '''Cancels when''' the defined number of elements has been taken or downstream cancels
 
 Parameters:
 
 n - (undocumented)
 
 Returns:
 
 (undocumented)
 - takeWithin
```
public SubFlow<In,Out,Mat> takeWithin(scala.concurrent.duration.FiniteDuration d)
```
 Terminate processing (and cancel the upstream publisher) after the given duration. Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
 Note that this can be combined with take(long) to limit the number of elements within the duration.
 '''Emits when''' an upstream element arrives
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or timer fires
 '''Cancels when''' downstream cancels or timer fires
 
 Parameters:
 
 d - (undocumented)
 
 Returns:
 
 (undocumented)
 - conflateWithSeed
```
public <S> SubFlow<In,S,Mat> conflateWithSeed(Function<Out,S> seed,
 Function2<S,Out,S> aggregate)
```
 Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary until the subscriber is ready to accept them. For example a conflate step might average incoming numbers if the upstream publisher is faster.
 This version of conflate allows to derive a seed from the first element and change the aggregated type to be different than the input type. See Flow.conflate for a simpler version that does not change types.
 This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not duplicate elements.
 '''Emits when''' downstream stops backpressuring and there is a conflated element available
 '''Backpressures when''' never
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 see also SubFlow.conflate SubFlow.batch SubFlow.batchWeighted
 
 Parameters:
 
 seed - Provides the first state for a conflated value using the first unconsumed element as a start
 
 aggregate - Takes the currently aggregated value and the current pending element to produce a new aggregate
 
 Returns:
 
 (undocumented)
 - conflate
```
public <O2> SubFlow<In,O2,Mat> conflate(Function2<O2,O2,O2> aggregate)
```
 Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary until the subscriber is ready to accept them. For example a conflate step might average incoming numbers if the upstream publisher is faster.
 This version of conflate does not change the output type of the stream. See SubFlow.conflateWithSeed for a more flexible version that can take a seed function and transform elements while rolling up.
 This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not duplicate elements.
 '''Emits when''' downstream stops backpressuring and there is a conflated element available
 '''Backpressures when''' never
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 see also SubFlow.conflateWithSeed SubFlow.batch SubFlow.batchWeighted
 
 Parameters:
 
 aggregate - Takes the currently aggregated value and the current pending element to produce a new aggregate
 
 Returns:
 
 (undocumented)
 - batch
```
public <S> SubFlow<In,S,Mat> batch(long max,
 Function<Out,S> seed,
 Function2<S,Out,S> aggregate)
```
 Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches until the subscriber is ready to accept them. For example a batch step might store received elements in an array up to the allowed max limit if the upstream publisher is faster.
 This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not duplicate elements.
 '''Emits when''' downstream stops backpressuring and there is an aggregated element available
 '''Backpressures when''' there are max batched elements and 1 pending element and downstream backpressures
 '''Completes when''' upstream completes and there is no batched/pending element waiting
 '''Cancels when''' downstream cancels
 See also SubFlow.conflate, SubFlow.batchWeighted
 
 Parameters:
 
 max - maximum number of elements to batch before backpressuring upstream (must be positive non-zero)
 
 seed - Provides the first state for a batched value using the first unconsumed element as a start
 
 aggregate - Takes the currently batched value and the current pending element to produce a new aggregate
 
 Returns:
 
 (undocumented)
 - batchWeighted
```
public <S> SubFlow<In,S,Mat> batchWeighted(long max,
 Function<Out,java.lang.Object> costFn,
 Function<Out,S> seed,
 Function2<S,Out,S> aggregate)
```
 Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches until the subscriber is ready to accept them. For example a batch step might concatenate ByteString elements up to the allowed max limit if the upstream publisher is faster.
 This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not duplicate elements.
 Batching will apply for all elements, even if a single element cost is greater than the total allowed limit. In this case, previous batched elements will be emitted, then the "heavy" element will be emitted (after being applied with the seed function) without batching further elements with it, and then the rest of the incoming elements are batched.
 '''Emits when''' downstream stops backpressuring and there is a batched element available
 '''Backpressures when''' there are max weighted batched elements + 1 pending element and downstream backpressures
 '''Completes when''' upstream completes and there is no batched/pending element waiting
 '''Cancels when''' downstream cancels
 See also SubFlow.conflate, SubFlow.batch
 
 Parameters:
 
 max - maximum weight of elements to batch before backpressuring upstream (must be positive non-zero)
 
 costFn - a function to compute a single element weight
 
 seed - Provides the first state for a batched value using the first unconsumed element as a start
 
 aggregate - Takes the currently batched value and the current pending element to produce a new batch
 
 Returns:
 
 (undocumented)
 - expand
```
public  SubFlow<In,U,Mat> expand(Function<Out,java.util.Iterator> extrapolate)
```
 Allows a faster downstream to progress independently of a slower publisher by extrapolating elements from an older element until new element comes from the upstream. For example an expand step might repeat the last element for the subscriber until it receives an update from upstream.
 This element will never "drop" upstream elements as all elements go through at least one extrapolation step. This means that if the upstream is actually faster than the upstream it will be backpressured by the downstream subscriber.
 Expand does not support Supervision.restart() and Supervision.resume(). Exceptions from the seed or extrapolate functions will complete the stream with failure.
 '''Emits when''' downstream stops backpressuring
 '''Backpressures when''' downstream backpressures or iterator runs empty
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 seed - Provides the first state for extrapolation using the first unconsumed element
 
 extrapolate - Takes the current extrapolation state to produce an output element and the next extrapolation state.
 
 Returns:
 
 (undocumented)
 - buffer
```
public SubFlow<In,Out,Mat> buffer(int size,
 OverflowStrategy overflowStrategy)
```
 Adds a fixed size buffer in the flow that allows to store elements from a faster upstream until it becomes full. Depending on the defined OverflowStrategy it might drop elements or backpressure the upstream if there is no space available
 '''Emits when''' downstream stops backpressuring and there is a pending element in the buffer
 '''Backpressures when''' depending on OverflowStrategy * Backpressure - backpressures when buffer is full * DropHead, DropTail, DropBuffer - never backpressures * Fail - fails the stream if buffer gets full
 '''Completes when''' upstream completes and buffered elements has been drained
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 size - The size of the buffer in element count
 
 overflowStrategy - Strategy that is used when incoming elements cannot fit inside the buffer
 
 Returns:
 
 (undocumented)
 - transform
```
public  SubFlow<In,U,Mat> transform(Creator<Stage<Out,U>> mkStage)
```
 Deprecated. Use via(GraphStage) instead. Since 2.4.3.
 
 Generic transformation of a stream with a custom processing Stage. This operator makes it possible to extend the Flow API when there is no specialized operator that performs the transformation.
 
 Parameters:
 
 mkStage - (undocumented)
 
 Returns:
 
 (undocumented)
 - prefixAndTail
```
public SubFlow<In,Pair<java.util.List<Out>,Source<Out,NotUsed>>,Mat> prefixAndTail(int n)
```
 Takes up to n elements from the stream (less than n only if the upstream completes before emitting n elements) and returns a pair containing a strict sequence of the taken element and a stream representing the remaining elements. If ''n'' is zero or negative, then this will return a pair of an empty collection and a stream containing the whole upstream unchanged.
 In case of an upstream error, depending on the current state - the master stream signals the error if less than n elements has been seen, and therefore the substream has not yet been emitted - the tail substream signals the error after the prefix and tail has been emitted by the main stream (at that point the main stream has already completed)
 '''Emits when''' the configured number of prefix elements are available. Emits this prefix, and the rest as a substream
 '''Backpressures when''' downstream backpressures or substream backpressures
 '''Completes when''' prefix elements has been consumed and substream has been consumed
 '''Cancels when''' downstream cancels or substream cancels
 
 Parameters:
 
 n - (undocumented)
 
 Returns:
 
 (undocumented)
 - flatMapConcat
```
public <T,M> SubFlow<In,T,Mat> flatMapConcat(Function<Out,? extends Graph<SourceShape<T>,M>> f)
```
 Transform each input element into a Source of output elements that is then flattened into the output stream by concatenation, fully consuming one Source after the other.
 '''Emits when''' a currently consumed substream has an element available
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes and all consumed substreams complete
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - flatMapMerge
```
public <T,M> SubFlow<In,T,Mat> flatMapMerge(int breadth,
 Function<Out,? extends Graph<SourceShape<T>,M>> f)
```
 Transform each input element into a Source of output elements that is then flattened into the output stream by merging, where at most breadth substreams are being consumed at any given time.
 '''Emits when''' a currently consumed substream has an element available
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes and all consumed substreams complete
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 breadth - (undocumented)
 
 f - (undocumented)
 
 Returns:
 
 (undocumented)
 - concat
```
public <T,M> SubFlow<In,T,Mat> concat(Graph<SourceShape<T>,M> that)
```
 Concatenate the given Source to this Flow, meaning that once this Flow’s input is exhausted and all result elements have been generated, the Source’s elements will be produced.
 Note that the Source is materialized together with this Flow and just kept from producing elements by asserting back-pressure until its time comes.
 If this Flow gets upstream error - no elements from the given Source will be pulled.
 '''Emits when''' element is available from current stream or from the given Source when current is completed
 '''Backpressures when''' downstream backpressures
 '''Completes when''' given Source completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 that - (undocumented)
 
 Returns:
 
 (undocumented)
 - prepend
```
public <T,M> SubFlow<In,T,Mat> prepend(Graph<SourceShape<T>,M> that)
```
 Prepend the given Source to this Flow, meaning that before elements are generated from this Flow, the Source's elements will be produced until it is exhausted, at which point Flow elements will start being produced.
 Note that this Flow will be materialized together with the Source and just kept from producing elements by asserting back-pressure until its time comes.
 If the given Source gets upstream error - no elements from this Flow will be pulled.
 '''Emits when''' element is available from the given Source or from current stream when the Source is completed
 '''Backpressures when''' downstream backpressures
 '''Completes when''' this Flow completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 that - (undocumented)
 
 Returns:
 
 (undocumented)
 - orElse
```
public <T,M> SubFlow<In,T,Mat> orElse(Graph<SourceShape<T>,M> secondary)
```
 Provides a secondary source that will be consumed if this source completes without any elements passing by. As soon as the first element comes through this stream, the alternative will be cancelled.
 Note that this Flow will be materialized together with the Source and just kept from producing elements by asserting back-pressure until its time comes or it gets cancelled.
 On errors the stage is failed regardless of source of the error.
 '''Emits when''' element is available from first stream or first stream closed without emitting any elements and an element is available from the second stream
 '''Backpressures when''' downstream backpressures
 '''Completes when''' the primary stream completes after emitting at least one element, when the primary stream completes without emitting and the secondary stream already has completed or when the secondary stream completes
 '''Cancels when''' downstream cancels and additionally the alternative is cancelled as soon as an element passes by from this stream.
 
 Parameters:
 
 secondary - (undocumented)
 
 Returns:
 
 (undocumented)
 - alsoTo
```
public SubFlow<In,Out,Mat> alsoTo(Graph<SinkShape<Out>,?> that)
```
 Attaches the given Sink to this Flow, meaning that elements that passes through will also be sent to the Sink.
 '''Emits when''' element is available and demand exists both from the Sink and the downstream.
 '''Backpressures when''' downstream or Sink backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 that - (undocumented)
 
 Returns:
 
 (undocumented)
 - merge
```
public <T> SubFlow<In,T,Mat> merge(Graph<SourceShape<T>,?> that)
```
 Merge the given Source to this Flow, taking elements as they arrive from input streams, picking randomly when several elements ready.
 '''Emits when''' one of the inputs has an element available
 '''Backpressures when''' downstream backpressures
 '''Completes when''' all upstreams complete
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 that - (undocumented)
 
 Returns:
 
 (undocumented)
 - interleave
```
public <T> SubFlow<In,T,Mat> interleave(Graph<SourceShape<T>,?> that,
 int segmentSize)
```
 Interleave is a deterministic merge of the given Source with elements of this Flow. It first emits segmentSize number of elements from this flow to downstream, then - same amount for that source, then repeat process.
 Example:
```
 Source(List(1, 2, 3)).interleave(List(4, 5, 6, 7), 2) // 1, 2, 4, 5, 3, 6, 7
 
```
 After one of upstreams is complete than all the rest elements will be emitted from the second one
 If it gets error from one of upstreams - stream completes with failure.
 '''Emits when''' element is available from the currently consumed upstream
 '''Backpressures when''' downstream backpressures. Signal to current upstream, switch to next upstream when received segmentSize elements
 '''Completes when''' the Flow and given Source completes
 '''Cancels when''' downstream cancels
 Parameters:
 
 that - (undocumented)
 
 segmentSize - (undocumented)
 
 Returns:
 
 (undocumented)
 - mergeSorted
```
public <U,M> SubFlow<In,U,Mat> mergeSorted(Graph<SourceShape,M> that,
 java.util.Comparator comp)
```
 Merge the given Source to this Flow, taking elements as they arrive from input streams, picking always the smallest of the available elements (waiting for one element from each side to be available). This means that possible contiguity of the input streams is not exploited to avoid waiting for elements, this merge will block when one of the inputs does not have more elements (and does not complete).
 '''Emits when''' all of the inputs have an element available
 '''Backpressures when''' downstream backpressures
 '''Completes when''' all upstreams complete
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 that - (undocumented)
 
 comp - (undocumented)
 
 Returns:
 
 (undocumented)
 - zip
```
public <T> SubFlow<In,scala.Tuple2<Out,T>,Mat> zip(Graph<SourceShape<T>,?> source)
```
 Combine the elements of current Flow and the given Source into a stream of tuples.
 '''Emits when''' all of the inputs has an element available
 '''Backpressures when''' downstream backpressures
 '''Completes when''' any upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 source - (undocumented)
 
 Returns:
 
 (undocumented)
 - zipWith
```
public <Out2,Out3> SubFlow<In,Out3,Mat> zipWith(Graph<SourceShape<Out2>,?> that,
 Function2<Out,Out2,Out3> combine)
```
 Put together the elements of current Flow and the given Source into a stream of combined elements using a combiner function.
 '''Emits when''' all of the inputs has an element available
 '''Backpressures when''' downstream backpressures
 '''Completes when''' any upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 that - (undocumented)
 
 combine - (undocumented)
 
 Returns:
 
 (undocumented)
 - zipWithIndex
```
public SubFlow<In,Pair<Out,java.lang.Object>,Mat> zipWithIndex()
```
 Combine the elements of current Flow into a stream of tuples consisting of all elements paired with their index. Indices start at 0.
 '''Emits when''' upstream emits an element and is paired with their index
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Returns:
 
 (undocumented)
 - initialTimeout
```
public SubFlow<In,Out,Mat> initialTimeout(scala.concurrent.duration.FiniteDuration timeout)
```
 If the first element has not passed through this stage before the provided timeout, the stream is failed with a TimeoutException.
 '''Emits when''' upstream emits an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or fails if timeout elapses before first element arrives
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 timeout - (undocumented)
 
 Returns:
 
 (undocumented)
 - completionTimeout
```
public SubFlow<In,Out,Mat> completionTimeout(scala.concurrent.duration.FiniteDuration timeout)
```
 If the completion of the stream does not happen until the provided timeout, the stream is failed with a TimeoutException.
 '''Emits when''' upstream emits an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or fails if timeout elapses before upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 timeout - (undocumented)
 
 Returns:
 
 (undocumented)
 - idleTimeout
```
public SubFlow<In,Out,Mat> idleTimeout(scala.concurrent.duration.FiniteDuration timeout)
```
 If the time between two processed elements exceeds the provided timeout, the stream is failed with a TimeoutException. The timeout is checked periodically, so the resolution of the check is one period (equals to timeout value).
 '''Emits when''' upstream emits an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or fails if timeout elapses between two emitted elements
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 timeout - (undocumented)
 
 Returns:
 
 (undocumented)
 - backpressureTimeout
```
public SubFlow<In,Out,Mat> backpressureTimeout(scala.concurrent.duration.FiniteDuration timeout)
```
 If the time between the emission of an element and the following downstream demand exceeds the provided timeout, the stream is failed with a TimeoutException. The timeout is checked periodically, so the resolution of the check is one period (equals to timeout value).
 '''Emits when''' upstream emits an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes or fails if timeout elapses between element emission and downstream demand.
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 timeout - (undocumented)
 
 Returns:
 
 (undocumented)
 - keepAlive
```
public  SubFlow<In,U,Mat> keepAlive(scala.concurrent.duration.FiniteDuration maxIdle,
 Creator injectedElem)
```
 Injects additional elements if upstream does not emit for a configured amount of time. In other words, this stage attempts to maintains a base rate of emitted elements towards the downstream.
 If the downstream backpressures then no element is injected until downstream demand arrives. Injected elements do not accumulate during this period.
 Upstream elements are always preferred over injected elements.
 '''Emits when''' upstream emits an element or if the upstream was idle for the configured period
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 maxIdle - (undocumented)
 
 injectedElem - (undocumented)
 
 Returns:
 
 (undocumented)
 - throttle
```
public SubFlow<In,Out,Mat> throttle(int elements,
 scala.concurrent.duration.FiniteDuration per,
 int maximumBurst,
 ThrottleMode mode)
```
 Sends elements downstream with speed limited to elements/per. In other words, this stage set the maximum rate for emitting messages. This combinator works for streams where all elements have the same cost or length.
 Throttle implements the token bucket model. There is a bucket with a given token capacity (burst size or maximumBurst). Tokens drops into the bucket at a given rate and can be spared for later use up to bucket capacity to allow some burstiness. Whenever stream wants to send an element, it takes as many tokens from the bucket as number of elements. If there isn't any, throttle waits until the bucket accumulates enough tokens. Bucket is full when stream just materialized and started.
 Parameter mode manages behaviour when upstream is faster than throttle rate: - akka.stream.ThrottleMode.Shaping makes pauses before emitting messages to meet throttle rate - akka.stream.ThrottleMode.Enforcing fails with exception when upstream is faster than throttle rate
 '''Emits when''' upstream emits an element and configured time per each element elapsed
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 elements - (undocumented)
 
 per - (undocumented)
 
 maximumBurst - (undocumented)
 
 mode - (undocumented)
 
 Returns:
 
 (undocumented)
 - throttle
```
public SubFlow<In,Out,Mat> throttle(int cost,
 scala.concurrent.duration.FiniteDuration per,
 int maximumBurst,
 Function<Out,java.lang.Integer> costCalculation,
 ThrottleMode mode)
```
 Sends elements downstream with speed limited to cost/per. Cost is calculating for each element individually by calling calculateCost function. This combinator works for streams when elements have different cost(length). Streams of ByteString for example.
 Throttle implements the token bucket model. There is a bucket with a given token capacity (burst size or maximumBurst). Tokens drops into the bucket at a given rate and can be spared for later use up to bucket capacity to allow some burstiness. Whenever stream wants to send an element, it takes as many tokens from the bucket as element cost. If there isn't any, throttle waits until the bucket accumulates enough tokens. Elements that costs more than the allowed burst will be delayed proportionally to their cost minus available tokens, meeting the target rate.
 Parameter mode manages behaviour when upstream is faster than throttle rate: - akka.stream.ThrottleMode.Shaping makes pauses before emitting messages to meet throttle rate - akka.stream.ThrottleMode.Enforcing fails with exception when upstream is faster than throttle rate. Enforcing cannot emit elements that cost more than the maximumBurst
 It is recommended to use non-zero burst sizes as they improve both performance and throttling precision by allowing the implementation to avoid using the scheduler when input rates fall below the enforced limit and to reduce most of the inaccuracy caused by the scheduler resolution (which is in the range of milliseconds).
 Throttler always enforces the rate limit, but in certain cases (mostly due to limited scheduler resolution) it enforces a tighter bound than what was prescribed. This can be also mitigated by increasing the burst size.
 '''Emits when''' upstream emits an element and configured time per each element elapsed
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 cost - (undocumented)
 
 per - (undocumented)
 
 maximumBurst - (undocumented)
 
 costCalculation - (undocumented)
 
 mode - (undocumented)
 
 Returns:
 
 (undocumented)
 - detach
```
public SubFlow<In,Out,Mat> detach()
```
 Detaches upstream demand from downstream demand without detaching the stream rates; in other words acts like a buffer of size 1.
 '''Emits when''' upstream emits an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Returns:
 
 (undocumented)
 - initialDelay
```
public SubFlow<In,Out,Mat> initialDelay(scala.concurrent.duration.FiniteDuration delay)
```
 Delays the initial element by the specified duration.
 '''Emits when''' upstream emits an element if the initial delay is already elapsed
 '''Backpressures when''' downstream backpressures or initial delay is not yet elapsed
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 delay - (undocumented)
 
 Returns:
 
 (undocumented)
 - withAttributes
```
public SubFlow<In,Out,Mat> withAttributes(Attributes attr)
```
 Change the attributes of this Source to the given ones and seal the list of attributes. This means that further calls will not be able to remove these attributes, but instead add new ones. Note that this operation has no effect on an empty Flow (because the attributes apply only to the contained processing stages).
 
 Parameters:
 
 attr - (undocumented)
 
 Returns:
 
 (undocumented)
 - addAttributes
```
public SubFlow<In,Out,Mat> addAttributes(Attributes attr)
```
 Add the given attributes to this Source. Further calls to withAttributes will not remove these attributes. Note that this operation has no effect on an empty Flow (because the attributes apply only to the contained processing stages).
 
 Parameters:
 
 attr - (undocumented)
 
 Returns:
 
 (undocumented)
 - named
```
public SubFlow<In,Out,Mat> named(java.lang.String name)
```
 Add a name attribute to this Flow.
 
 Parameters:
 
 name - (undocumented)
 
 Returns:
 
 (undocumented)
 - async
```
public SubFlow<In,Out,Mat> async()
```
 Put an asynchronous boundary around this SubFlow
 
 Returns:
 
 (undocumented)
 - log
```
public SubFlow<In,Out,Mat> log(java.lang.String name,
 Function<Out,java.lang.Object> extract,
 LoggingAdapter log)
```
 Logs elements flowing through the stream as well as completion and erroring.
 By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be adjusted according to your needs by providing a custom Attributes.LogLevels attribute on the given Flow:
 The extract function will be applied to each element before logging, so it is possible to log only those fields of a complex object flowing through this element.
 Uses the given LoggingAdapter for logging.
 '''Emits when''' the mapping function returns an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 name - (undocumented)
 
 extract - (undocumented)
 
 log - (undocumented)
 
 Returns:
 
 (undocumented)
 - log
```
public SubFlow<In,Out,Mat> log(java.lang.String name,
 Function<Out,java.lang.Object> extract)
```
 Logs elements flowing through the stream as well as completion and erroring.
 By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be adjusted according to your needs by providing a custom Attributes.LogLevels attribute on the given Flow:
 The extract function will be applied to each element before logging, so it is possible to log only those fields of a complex object flowing through this element.
 Uses an internally created LoggingAdapter which uses akka.stream.Log as it's source (use this class to configure slf4j loggers).
 '''Emits when''' the mapping function returns an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 name - (undocumented)
 
 extract - (undocumented)
 
 Returns:
 
 (undocumented)
 - log
```
public SubFlow<In,Out,Mat> log(java.lang.String name,
 LoggingAdapter log)
```
 Logs elements flowing through the stream as well as completion and erroring.
 By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be adjusted according to your needs by providing a custom Attributes.LogLevels attribute on the given Flow:
 Uses the given LoggingAdapter for logging.
 '''Emits when''' the mapping function returns an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 name - (undocumented)
 
 log - (undocumented)
 
 Returns:
 
 (undocumented)
 - log
```
public SubFlow<In,Out,Mat> log(java.lang.String name)
```
 Logs elements flowing through the stream as well as completion and erroring.
 By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be adjusted according to your needs by providing a custom Attributes.LogLevels attribute on the given Flow.
 Uses an internally created LoggingAdapter which uses akka.stream.Log as it's source (use this class to configure slf4j loggers).
 '''Emits when''' the mapping function returns an element
 '''Backpressures when''' downstream backpressures
 '''Completes when''' upstream completes
 '''Cancels when''' downstream cancels
 
 Parameters:
 
 name - (undocumented)
 
 Returns:
 
 (undocumented)

Class SubFlow<In,Out,Mat>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

SubFlow

Method Detail

asScala

mergeSubstreams

mergeSubstreamsWithParallelism

concatSubstreams

via

to

map

mapConcat

statefulMapConcat

mapAsync

mapAsyncUnordered

filter

filterNot

collect

grouped

limit

limitWeighted

sliding

scan

scanAsync

fold

foldAsync

reduce

intersperse

intersperse

groupedWithin

delay

drop

dropWithin

takeWhile

takeWhile

dropWhile

recover

recoverWith

recoverWithRetries

mapError

take

takeWithin

conflateWithSeed

conflate

batch

batchWeighted

expand

buffer

transform

prefixAndTail

flatMapConcat

flatMapMerge

concat

prepend

orElse

alsoTo

merge

interleave

mergeSorted

zip

zipWith

zipWithIndex

initialTimeout

completionTimeout

idleTimeout

backpressureTimeout

keepAlive

throttle

throttle

detach

initialDelay

withAttributes

addAttributes

named

async

log

log