Package org.consensusj.analytics.util.collector

Class LargestSliceCollector<E,N extends Number & Comparable<? super N>>

java.lang.Object

org.consensusj.analytics.util.collector.LargestSliceCollector<E,N>

Type Parameters:

E - The type of objects

N - The subclass of Number to use, must be Comparable

All Implemented Interfaces:

Collector<E,LargestSliceAccumulator<E,N>,LargestSliceList<E,N>>

public class LargestSliceCollector<E,N extends Number & Comparable<? super N>>
extends Object
implements Collector<E,LargestSliceAccumulator<E,N>,LargestSliceList<E,N>>

Collector that collects the n objects containing the "largest slices" of an input stream of type <E>. Each object must have a numeric "slice size" of type <N> determined by a sliceSizeExtractor provided to the constructor. The result is a LargestSliceList containing the n largest slices (LargestSliceList.getSliceList()) and the sum of the slice sizes (LargestSliceList.getTotalOther()) of the filtered/excluded objects. The idea is the results can easily be converted to a Pie Chart.

The objects streamed must be unique, non-null, and a sliceSizeExtractor must be provided that will return a Comparable subclass of Number. The internal LargestSliceAccumulator is a mutable implementation of LargestSliceList

Note: Be careful to use only a single sliceSizeExtractor or you can end up with LargestSliceList objects with incompatible search orders (comparators).

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.stream.Collector

Collector.Characteristics

Constructor Summary

Constructors

Constructor	Description
LargestSliceCollector(int n, Function<E,N> sliceSizeExtractor, N zero, BinaryOperator<N> additionOperator)	Construct a LargestSliceCollector to collect n objects of type <E>.

Method Summary

Modifier and Type	Method	Description
BiConsumer<LargestSliceAccumulator<E,N>,E>	accumulator()
Set<Collector.Characteristics>	characteristics()	Note that our accumulator won't work correctly or efficiently if a single accumulator is used from multiple threads.
BinaryOperator<LargestSliceAccumulator<E,N>>	combiner()
Function<LargestSliceAccumulator<E,N>,LargestSliceList<E,N>>	finisher()	Return a finisher function.
Supplier<LargestSliceAccumulator<E,N>>	supplier()

Methods inherited from class java.lang.Object

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

Constructor Details

LargestSliceCollector

public LargestSliceCollector(int n,
 Function<E,N> sliceSizeExtractor,
 N zero,
 BinaryOperator<N> additionOperator)

Construct a LargestSliceCollector to collect n objects of type <E>. The remaining constructor parameters provide support for the necessary internal calculations for types <E> and <N>.

Parameters:

n - Number of "slices" to collect

sliceSizeExtractor - A Function to return the slice size of an object

zero - The value of zero for type N

additionOperator - addition operator for type N

Method Details

supplier

public Supplier<LargestSliceAccumulator<E,N>> supplier()

Specified by:

supplier in interface Collector<E,LargestSliceAccumulator<E,N extends Number & Comparable<? super N>>,LargestSliceList<E,N extends Number & Comparable<? super N>>>

accumulator

public BiConsumer<LargestSliceAccumulator<E,N>,E> accumulator()

Specified by:

accumulator in interface Collector<E,LargestSliceAccumulator<E,N extends Number & Comparable<? super N>>,LargestSliceList<E,N extends Number & Comparable<? super N>>>

combiner

public BinaryOperator<LargestSliceAccumulator<E,N>> combiner()

Specified by:

combiner in interface Collector<E,LargestSliceAccumulator<E,N extends Number & Comparable<? super N>>,LargestSliceList<E,N extends Number & Comparable<? super N>>>

finisher

public Function<LargestSliceAccumulator<E,N>,LargestSliceList<E,N>> finisher()

Return a finisher function.

Specified by:

finisher in interface Collector<E,LargestSliceAccumulator<E,N extends Number & Comparable<? super N>>,LargestSliceList<E,N extends Number & Comparable<? super N>>>

Returns:

A finisher function

characteristics

public Set<Collector.Characteristics> characteristics()

Note that our accumulator won't work correctly or efficiently if a single accumulator is used from multiple threads. It works with parallel streams, but not with a CONCURRENT collector. See: https://stackoverflow.com/questions/22350288/parallel-streams-collectors-and-thread-safety

Specified by:

characteristics in interface Collector<E,LargestSliceAccumulator<E,N extends Number & Comparable<? super N>>,LargestSliceList<E,N extends Number & Comparable<? super N>>>

Returns:

The characteristics of this collector.