Gatherer

public interface Gatherer

java.util.stream.Gatherer<T, A, R>

An intermediate operation that transforms a stream of input elements into a stream of output elements, optionally applying a final action when the end of the upstream is reached. The transformation may be stateless or stateful, and may buffer input before producing any output.

Gatherer operations can be performed either sequentially, or be parallelized -- if a combiner function is supplied.

There are many examples of gathering operations, including but not limited to: grouping elements into batches (windowing functions); de-duplicating consecutively similar elements; incremental accumulation functions (prefix scan); incremental reordering functions, etc. The class Gatherers provides implementations of common gathering operations.

See also:

Summary

Nested classes
`interface`	`Gatherer.Downstream<T>` A Downstream object is the next stage in a pipeline of operations, to which elements can be sent.
`interface`	`Gatherer.Integrator<A, T, R>` An Integrator receives elements and processes them, optionally using the supplied state, and optionally sends incremental results downstream.

Public methods
`default <RR> Gatherer<T, ?, RR>`	`andThen(Gatherer<? super R, ?, ? extends RR> that)` Returns a composed Gatherer which connects the output of this Gatherer to the input of that Gatherer.
`default BinaryOperator<A>`	`combiner()` A function which accepts two intermediate states and combines them into one.
`static <A> BinaryOperator<A>`	`defaultCombiner()` Returns a combiner which is the default combiner of a Gatherer.
`static <A, R> BiConsumer<A, Downstream<? super R>>`	`defaultFinisher()` Returns a `finisher` which is the default finisher of a `Gatherer`.
`static <A> Supplier<A>`	`defaultInitializer()` Returns an initializer which is the default initializer of a Gatherer.
`default BiConsumer<A, Downstream<? super R>>`	`finisher()` A function which accepts the final intermediate state and a `Downstream` object, allowing to perform a final action at the end of input elements.
`default Supplier<A>`	`initializer()` A function that produces an instance of the intermediate state used for this gathering operation.
`abstract Integrator<A, T, R>`	`integrator()` A function which integrates provided elements, potentially using the provided intermediate state, optionally producing output to the provided `Downstream`.
`static <T, R> Gatherer<T, Void, R>`	`of(Integrator<Void, T, R> integrator)` Returns a new, parallelizable, and stateless `Gatherer` described by the given `integrator`.
`static <T, A, R> Gatherer<T, A, R>`	`of(Supplier<A> initializer, Integrator<A, T, R> integrator, BinaryOperator<A> combiner, BiConsumer<A, Downstream<? super R>> finisher)` Returns a new, parallelizable, `Gatherer` described by the given `initializer`, `integrator`, `combiner` and `finisher`.
`static <T, R> Gatherer<T, Void, R>`	`of(Integrator<Void, T, R> integrator, BiConsumer<Void, Downstream<? super R>> finisher)` Returns a new, parallelizable, and stateless `Gatherer` described by the given `integrator` and `finisher`.
`static <T, A, R> Gatherer<T, A, R>`	`ofSequential(Supplier<A> initializer, Integrator<A, T, R> integrator)` Returns a new, sequential, `Gatherer` described by the given `initializer` and `integrator`.
`static <T, A, R> Gatherer<T, A, R>`	`ofSequential(Supplier<A> initializer, Integrator<A, T, R> integrator, BiConsumer<A, Downstream<? super R>> finisher)` Returns a new, sequential, `Gatherer` described by the given `initializer`, `integrator`, and `finisher`.
`static <T, R> Gatherer<T, Void, R>`	`ofSequential(Integrator<Void, T, R> integrator, BiConsumer<Void, Downstream<? super R>> finisher)` Returns a new, sequential, and stateless `Gatherer` described by the given `integrator` and `finisher`.
`static <T, R> Gatherer<T, Void, R>`	`ofSequential(Integrator<Void, T, R> integrator)` Returns a new, sequential, and stateless `Gatherer` described by the given `integrator`.

Parameters
`initializer`	`Supplier`: the initializer function for the new gatherer
`integrator`	`Integrator`: the integrator function for the new gatherer
`combiner`	`BinaryOperator`: the combiner function for the new gatherer
`finisher`	`BiConsumer`: the finisher function for the new gatherer

Gatherer

Summary

Nested classes

Public methods

Public methods

andThen

Implementation Requirements:

combiner

Implementation Requirements:

defaultCombiner

Implementation Requirements:

defaultFinisher

Implementation Requirements:

defaultInitializer

Implementation Requirements:

finisher

Implementation Requirements:

initializer

Implementation Requirements:

integrator

of

of

of

ofSequential

ofSequential

ofSequential

ofSequential