com.aol.cyclops

Class Reducers

java.lang.Object

com.aol.cyclops.Reducers

public class Reducers
extends java.lang.Object

Class that holds Reducers, Monoids with a type conversion for reducing a dataset to a single value. Primary use case is the reduction of Streams to persistent collections e.g.

  
 PQueueX<Integer> q = Reducers.<Integer>toPQueueX()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Use with care, as the mapReduce method is not type safe

Constructor Summary

Constructors

Constructor and Description
Reducers()

Method Summary

Modifier and Type	Method and Description
static Reducer<java.lang.Double>	toCountDouble()
static Reducer<java.lang.Integer>	toCountInt()
static <T> Reducer<org.pcollections.PBag<T>>	toPBag() PBag<Integer> q = Reducers.<Integer>toPBag() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<PBagX<T>>	toPBagX() PBagX<Integer> q = Reducers.<Integer>toPBagX() .mapReduce(Stream.of(1,2,3,4));
static <K,V> Reducer<org.pcollections.PMap<K,V>>	toPMap() PMap<Integer,String> q = Reducers.<Integer,String>toPMap() .mapReduce(Stream.of(Arrays.asList("hello",1),Arrays.asList("world",2)));
static <K,V> Reducer<PMapX<K,V>>	toPMapX() PMapX<Integer,String> q = Reducers.<Integer,String>toPMapX() .mapReduce(Stream.of(Arrays.asList("hello",1),Arrays.asList("world",2)));
static <T> Reducer<org.pcollections.POrderedSet<T>>	toPOrderedSet() POrderedSet<Integer> q = Reducers.<Integer>toPOrderedSet() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<POrderedSetX<T>>	toPOrderedSetX() POrderedSetX<Integer> q = Reducers.<Integer>toPOrderedSetX() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<org.pcollections.PQueue<T>>	toPQueue() PQueue<Integer> q = Reducers.<Integer>toPQueue() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<PQueueX<T>>	toPQueueX() PQueueX<Integer> q = Reducers.<Integer>toPQueueX() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<org.pcollections.PSet<T>>	toPSet() PSet<Integer> q = Reducers.<Integer>toPSet() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<PSetX<T>>	toPSetX() PSetX<Integer> q = Reducers.<Integer>toPSetX() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<org.pcollections.PStack<T>>	toPStack() PStack<Integer> q = Reducers.<Integer>toPStack() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<org.pcollections.PStack<T>>	toPStackReversed() PStack<Integer> q = Reducers.<Integer>toPStackReversed() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<PStackX<T>>	toPStackX() PStackX<Integer> q = Reducers.<Integer>toPStackX() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<org.pcollections.PVector<T>>	toPVector() PVector<Integer> q = Reducers.<Integer>toPVector() .mapReduce(Stream.of(1,2,3,4));
static <T> Reducer<PVectorX<T>>	toPVectorX() PVectorX<Integer> q = Reducers.<Integer>toPVectorX() .mapReduce(Stream.of(1,2,3,4));
static Monoid<java.lang.String>	toString(java.lang.String joiner) Monoid for String concatonation
static Monoid<java.lang.Double>	toTotalDouble()
static Monoid<java.lang.Integer>	toTotalInt()

Methods inherited from class java.lang.Object

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

Constructor Detail

Reducers

public Reducers()

Method Detail

toPQueueX

public static <T> Reducer<PQueueX<T>> toPQueueX()

  
 PQueueX<Integer> q = Reducers.<Integer>toPQueueX()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer to PQueueX types

toPOrderedSetX

public static <T> Reducer<POrderedSetX<T>> toPOrderedSetX()

  
 POrderedSetX<Integer> q = Reducers.<Integer>toPOrderedSetX()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer to POrderedSetX

toPSetX

public static <T> Reducer<PSetX<T>> toPSetX()

  
 PSetX<Integer> q = Reducers.<Integer>toPSetX()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PSetX

toPStackX

public static <T> Reducer<PStackX<T>> toPStackX()

  
 PStackX<Integer> q = Reducers.<Integer>toPStackX()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PStackX

toPVectorX

public static <T> Reducer<PVectorX<T>> toPVectorX()

  
 PVectorX<Integer> q = Reducers.<Integer>toPVectorX()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PVectorX

toPBagX

public static <T> Reducer<PBagX<T>> toPBagX()

  
 PBagX<Integer> q = Reducers.<Integer>toPBagX()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PBagX

toPQueue

public static <T> Reducer<org.pcollections.PQueue<T>> toPQueue()

  
 PQueue<Integer> q = Reducers.<Integer>toPQueue()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer to PQueue types

toPOrderedSet

public static <T> Reducer<org.pcollections.POrderedSet<T>> toPOrderedSet()

  
 POrderedSet<Integer> q = Reducers.<Integer>toPOrderedSet()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer to POrderedSet

toPBag

public static <T> Reducer<org.pcollections.PBag<T>> toPBag()

  
 PBag<Integer> q = Reducers.<Integer>toPBag()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PBag

toPSet

public static <T> Reducer<org.pcollections.PSet<T>> toPSet()

  
 PSet<Integer> q = Reducers.<Integer>toPSet()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PSet

toPVector

public static <T> Reducer<org.pcollections.PVector<T>> toPVector()

  
 PVector<Integer> q = Reducers.<Integer>toPVector()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PVector

toPStack

public static <T> Reducer<org.pcollections.PStack<T>> toPStack()

  
 PStack<Integer> q = Reducers.<Integer>toPStack()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PStack

toPStackReversed

public static <T> Reducer<org.pcollections.PStack<T>> toPStackReversed()

  
 PStack<Integer> q = Reducers.<Integer>toPStackReversed()
                                .mapReduce(Stream.of(1,2,3,4));
 
 
 

Returns:

Reducer for PStack in reveresed order

toPMap

public static <K,V> Reducer<org.pcollections.PMap<K,V>> toPMap()

  
 PMap<Integer,String> q = Reducers.<Integer,String>toPMap()
                                .mapReduce(Stream.of(Arrays.asList("hello",1),Arrays.asList("world",2)));
 
 
 

Returns:

Reducer for PMap

toPMapX

public static <K,V> Reducer<PMapX<K,V>> toPMapX()

  
 PMapX<Integer,String> q = Reducers.<Integer,String>toPMapX()
                                        .mapReduce(Stream.of(Arrays.asList("hello",1),Arrays.asList("world",2)));
 
 
 

Returns:

Reducer for PMapX

toString

public static Monoid<java.lang.String> toString(java.lang.String joiner)

Monoid for String concatonation

Parameters:

joiner - String combiner

Returns:

toTotalInt

public static Monoid<java.lang.Integer> toTotalInt()

Returns:

Monoid for summing Ints

toCountInt

public static Reducer<java.lang.Integer> toCountInt()

Returns:

Reducer for counting number of values

toTotalDouble

public static Monoid<java.lang.Double> toTotalDouble()

Returns:

Monoid for summing doubles

toCountDouble

public static Reducer<java.lang.Double> toCountDouble()

Returns:

Reducer for counting doubles by converting toString to Double.valueOf( )