Added in API level Baklava

Gatherer

interface Gatherer<T : Any!, A : Any!, R : Any!>

java.util.stream.Gatherer

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 java.util.stream.Gatherers provides implementations of common gathering operations.

Summary

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

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

Public methods

andThen

Added in API level Baklava

open fun <RR : Any!> andThen(that: Gatherer<in R, *, out RR>!): Gatherer<T, *, RR>!

Returns a composed Gatherer which connects the output of this Gatherer to the input of that Gatherer.

Parameters
`that`	Gatherer<in R, *, out RR>!: the other gatherer
`<RR>`	The type of output of that Gatherer

Return
`Gatherer<T, *, RR>!`	returns a composed Gatherer which connects the output of this Gatherer as input that Gatherer

Exceptions
`java.lang.NullPointerException`	if the argument is `null`

combiner

Added in API level Baklava

open fun combiner(): BinaryOperator<A>!

A function which accepts two intermediate states and combines them into one.

Return
`BinaryOperator<A>!`	a function which accepts two intermediate states and combines them into one

defaultCombiner

Added in API level Baklava

open static fun <A : Any!> defaultCombiner(): BinaryOperator<A>!

Returns a combiner which is the default combiner of a Gatherer. The returned combiner identifies that the owning Gatherer must only be evaluated sequentially.

Parameters
`<A>`	the type of the state of the returned combiner

Return
`BinaryOperator<A>!`	the instance of the default combiner

See Also

java.util.stream.Gatherer#combiner()

defaultFinisher

Added in API level Baklava

open static fun <A : Any!, R : Any!> defaultFinisher(): BiConsumer<A, Gatherer.Downstream<in R>!>!

Returns a finisher which is the default finisher of a Gatherer. The returned finisher identifies that the owning Gatherer performs no additional actions at the end of input.

Parameters
`<A>`	the type of the state of the returned finisher
`<R>`	the type of the Downstream of the returned finisher

Return
`BiConsumer<A, Gatherer.Downstream<in R>!>!`	the instance of the default finisher

See Also

java.util.stream.Gatherer#finisher()

defaultInitializer

Added in API level Baklava

open static fun <A : Any!> defaultInitializer(): Supplier<A>!

Returns an initializer which is the default initializer of a Gatherer. The returned initializer identifies that the owner Gatherer is stateless.

Parameters
`<A>`	the type of the state of the returned initializer

Return
`Supplier<A>!`	the instance of the default initializer

See Also

java.util.stream.Gatherer#initializer()

finisher

Added in API level Baklava

open fun finisher(): BiConsumer<A, Gatherer.Downstream<in R>!>!

A function which accepts the final intermediate state and a Downstream object, allowing to perform a final action at the end of input elements.

Return
`BiConsumer<A, Gatherer.Downstream<in R>!>!`	a function which transforms the intermediate result to the final result(s) which are then passed on to the provided Downstream

initializer

Added in API level Baklava

open fun initializer(): Supplier<A>!

A function that produces an instance of the intermediate state used for this gathering operation.

Return
`Supplier<A>!`	A function that produces an instance of the intermediate state used for this gathering operation

integrator

Added in API level Baklava

abstract fun integrator(): Gatherer.Integrator<A, T, R>!

A function which integrates provided elements, potentially using the provided intermediate state, optionally producing output to the provided Downstream.

Return
`Gatherer.Integrator<A, T, R>!`	a function which integrates provided elements, potentially using the provided state, optionally producing output to the provided Downstream

of

Added in API level Baklava

open static fun <T : Any!, A : Any!, R : Any!> of(
    initializer: Supplier<A>!, 
    integrator: Gatherer.Integrator<A, T, R>!, 
    combiner: BinaryOperator<A>!, 
    finisher: BiConsumer<A, Gatherer.Downstream<in R>!>!
): Gatherer<T, A, R>!

Returns a new, parallelizable, Gatherer described by the given initializer, integrator, combiner and finisher.

Parameters
`initializer`	Supplier<A>!: the initializer function for the new gatherer
`integrator`	Gatherer.Integrator<A, T, R>!: the integrator function for the new gatherer
`combiner`	BinaryOperator<A>!: the combiner function for the new gatherer
`finisher`	BiConsumer<A, Gatherer.Downstream<in R>!>!: the finisher function for the new gatherer
`<T>`	the type of input elements for the new gatherer
`<A>`	the type of state for the new gatherer
`<R>`	the type of results for the new gatherer

Return
`Gatherer<T, A, R>!`	the new `Gatherer`

Exceptions
`java.lang.NullPointerException`	if any argument is `null`

of

Added in API level Baklava

open static fun <T : Any!, R : Any!> of(integrator: Gatherer.Integrator<Void!, T, R>!): Gatherer<T, Void!, R>!

Returns a new, parallelizable, and stateless Gatherer described by the given integrator.

Parameters
`integrator`	Gatherer.Integrator<Void!, T, R>!: the integrator function for the new gatherer
`<T>`	the type of input elements for the new gatherer
`<R>`	the type of results for the new gatherer

Return
`Gatherer<T, Void!, R>!`	the new `Gatherer`

Exceptions
`java.lang.NullPointerException`	if any argument is `null`

of

Added in API level Baklava

open static fun <T : Any!, R : Any!> of(
    integrator: Gatherer.Integrator<Void!, T, R>!, 
    finisher: BiConsumer<Void!, Gatherer.Downstream<in R>!>!
): Gatherer<T, Void!, R>!

Returns a new, parallelizable, and stateless Gatherer described by the given integrator and finisher.

Parameters
`integrator`	Gatherer.Integrator<Void!, T, R>!: the integrator function for the new gatherer
`finisher`	BiConsumer<Void!, Gatherer.Downstream<in R>!>!: the finisher function for the new gatherer
`<T>`	the type of input elements for the new gatherer
`<R>`	the type of results for the new gatherer

Return
`Gatherer<T, Void!, R>!`	the new `Gatherer`

Exceptions
`java.lang.NullPointerException`	if any argument is `null`

ofSequential

Added in API level Baklava

open static fun <T : Any!, A : Any!, R : Any!> ofSequential(
    initializer: Supplier<A>!, 
    integrator: Gatherer.Integrator<A, T, R>!
): Gatherer<T, A, R>!

Returns a new, sequential, Gatherer described by the given initializer and integrator.

Parameters
`initializer`	Supplier<A>!: the initializer function for the new gatherer
`integrator`	Gatherer.Integrator<A, T, R>!: the integrator function for the new gatherer
`<T>`	the type of input elements for the new gatherer
`<A>`	the type of state for the new gatherer
`<R>`	the type of results for the new gatherer

Return
`Gatherer<T, A, R>!`	the new `Gatherer`

Exceptions
`java.lang.NullPointerException`	if any argument is `null`

ofSequential

Added in API level Baklava

open static fun <T : Any!, A : Any!, R : Any!> ofSequential(
    initializer: Supplier<A>!, 
    integrator: Gatherer.Integrator<A, T, R>!, 
    finisher: BiConsumer<A, Gatherer.Downstream<in R>!>!
): Gatherer<T, A, R>!

Returns a new, sequential, Gatherer described by the given initializer, integrator, and finisher.

Parameters
`initializer`	Supplier<A>!: the initializer function for the new gatherer
`integrator`	Gatherer.Integrator<A, T, R>!: the integrator function for the new gatherer
`finisher`	BiConsumer<A, Gatherer.Downstream<in R>!>!: the finisher function for the new gatherer
`<T>`	the type of input elements for the new gatherer
`<A>`	the type of state for the new gatherer
`<R>`	the type of results for the new gatherer

Return
`Gatherer<T, A, R>!`	the new `Gatherer`

Exceptions
`java.lang.NullPointerException`	if any argument is `null`

ofSequential

Added in API level Baklava

open static fun <T : Any!, R : Any!> ofSequential(integrator: Gatherer.Integrator<Void!, T, R>!): Gatherer<T, Void!, R>!

Returns a new, sequential, and stateless Gatherer described by the given integrator.

Parameters
`integrator`	Gatherer.Integrator<Void!, T, R>!: the integrator function for the new gatherer
`<T>`	the type of input elements for the new gatherer
`<R>`	the type of results for the new gatherer

Return
`Gatherer<T, Void!, R>!`	the new `Gatherer`

Exceptions
`java.lang.NullPointerException`	if the argument is `null`

ofSequential

Added in API level Baklava

open static fun <T : Any!, R : Any!> ofSequential(
    integrator: Gatherer.Integrator<Void!, T, R>!, 
    finisher: BiConsumer<Void!, Gatherer.Downstream<in R>!>!
): Gatherer<T, Void!, R>!

Returns a new, sequential, and stateless Gatherer described by the given integrator and finisher.

Parameters
`integrator`	Gatherer.Integrator<Void!, T, R>!: the integrator function for the new gatherer
`finisher`	BiConsumer<Void!, Gatherer.Downstream<in R>!>!: the finisher function for the new gatherer
`<T>`	the type of input elements for the new gatherer
`<R>`	the type of results for the new gatherer

Return
`Gatherer<T, Void!, R>!`	the new `Gatherer`

Exceptions
`java.lang.NullPointerException`	if any argument is `null`