Package org.aksw.commons.util.stream

Class CollapseRunsSpecBase<T,K,V>

java.lang.Object

org.aksw.commons.util.stream.CollapseRunsSpecBase<T,K,V>

Type Parameters:

T - The upstream (input) item type

K - The key type by which to group items

V - The type of the result of grouping items

Direct Known Subclasses:

CollapseRunsOperationBase, CollapseRunsSpec

public class CollapseRunsSpecBase<T,K,V>
extends Object

Base class with core attributes for partial reduction of consecutive items sharing some attribute (referred to as group key). This class is shared between specification and operation implementations. The most similar implementation I am aware of is https://github.com/amaembo/streamex/blob/master/src/main/java/one/util/streamex/CollapseSpliterator.java There are minor differences in the models though: - Sequential group by only creates a single accumulator per group and feeds all consecutive items to it. - StreamEx seems to create multiple accumulators together with a combine function When accumulating consecutive triples into a graph it does not make much sense having to combine individual graphs as this is quite an expensive operation due to the unnecessary indexing overhead involved. (i.e. indexing of triples only to combine them afterwards anyway)

Author:

raven

Field Summary

Fields

Modifier and Type	Field	Description
protected BiFunction<? super V,? super T,? extends V>	accAdd	Reduce an item with the accumulator to obtain a new accumulator
protected BiFunction<? super Long,? super K,? extends V>	accCtor	Constructor function for accumulators.
protected Function<? super T,? extends K>	getGroupKey	Function to derive a group key from an item in the flow
protected BiPredicate<? super K,? super K>	groupKeyCompare	Comparison whether two group keys are equal

Constructor Summary

Constructors

Constructor	Description
CollapseRunsSpecBase(Function<? super T,? extends K> getGroupKey, BiPredicate<? super K,? super K> groupKeyCompare, BiFunction<? super Long,? super K,? extends V> accCtor, BiFunction<? super V,? super T,? extends V> accAdd)
CollapseRunsSpecBase(CollapseRunsSpecBase<T,K,V> other)

Method Summary

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

getGroupKey

protected Function<? super T,? extends K> getGroupKey

Function to derive a group key from an item in the flow

groupKeyCompare

protected BiPredicate<? super K,? super K> groupKeyCompare

Comparison whether two group keys are equal

accCtor

protected BiFunction<? super Long,? super K,? extends V> accCtor

Constructor function for accumulators. Receives item index and group key

accAdd

protected BiFunction<? super V,? super T,? extends V> accAdd

Reduce an item with the accumulator to obtain a new accumulator

Constructor Details

CollapseRunsSpecBase

public CollapseRunsSpecBase(CollapseRunsSpecBase<T,K,V> other)

CollapseRunsSpecBase

public CollapseRunsSpecBase(Function<? super T,? extends K> getGroupKey,
 BiPredicate<? super K,? super K> groupKeyCompare,
 BiFunction<? super Long,? super K,? extends V> accCtor,
 BiFunction<? super V,? super T,? extends V> accAdd)