Module io.smallrye.mutiny

Package io.smallrye.mutiny.groups

Interface Gatherer<I,ACC,O>

Type Parameters:

I - the type of the items emitted by the upstream

ACC - the type of the accumulator

O - the type of the items emitted to the downstream

All Known Implementing Classes:

Gatherers.DefaultGatherer

@Experimental("This API is still being designed and may change in the future")
public interface Gatherer<I,ACC,O>

A Gatherer operator transforms a stream of items by accumulating them into an accumulator and extracting items from that accumulator when certain conditions are met.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	Gatherer.Builder<I>	Builder for creating a Gatherer.
static final record	Gatherer.Extraction<ACC,O>	An extraction result containing the next accumulator and the next item to emit.
static class	Gatherer.ExtractStep<I,ACC>	The second step in the builder to gather items emitted by a Multi into an accumulator.
static class	Gatherer.FinalizerStep<I,ACC,O>	The third step in the builder to gather items emitted by a Multi into an accumulator.
static class	Gatherer.InitialAccumulatorStep<I,ACC>	The first step in the builder to gather items emitted by a Multi into an accumulator.

Method Summary

Modifier and Type	Method	Description
ACC	accumulate(ACC accumulator, I item)	Accumulates an item into the accumulator.
ACC	accumulator()	Creates a new accumulator.
Optional<Gatherer.Extraction<ACC,O>>	extract(ACC accumulator, boolean upstreamCompleted)	Extracts an item from the accumulator.
Optional<O>	finalize(ACC accumulator)	Finalizes the accumulator and extracts the final item, if any.

Method Details

accumulator

ACC accumulator()

Creates a new accumulator.

Returns:

a new accumulator

accumulate

ACC accumulate(ACC accumulator,
 I item)

Accumulates an item into the accumulator.

Parameters:

accumulator - the current accumulator

item - the item to accumulate

Returns:

the updated accumulator

extract

Optional<Gatherer.Extraction<ACC,O>> extract(ACC accumulator,
 boolean upstreamCompleted)

Extracts an item from the accumulator.

Parameters:

accumulator - the current accumulator

upstreamCompleted - whether the upstream has completed

Returns:

an Optional containing a Extraction with the updated accumulator and the extracted item, or an empty Optional if no item can be extracted

finalize

Optional<O> finalize(ACC accumulator)

Finalizes the accumulator and extracts the final item, if any. This method is called when the upstream has completed and no more items can be extracted using the extract method.

Parameters:

accumulator - the current accumulator

Returns:

an Optional containing the final item, or an empty Optional if no final item can be extracted