blasd.apex.core.stream

Class ApexStreamHelper

java.lang.Object

blasd.apex.core.stream.ApexStreamHelper

public class ApexStreamHelper
extends Object

Various helpers for Java8 Stream

Author:

Benoit Lacelle

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.slf4j.Logger	LOGGER

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ApexStreamHelper()

Method Summary

Modifier and Type	Method and Description
static <T> long	consumeByPartition(Stream<T> stream, Consumer<Queue<T>> consumer, int partitionSize) Enable consuming a stream by blocks of size controlled by the Queue
static <T> long	consumeByPartition(Supplier<? extends BlockingQueue<T>> queueSupplier, Stream<T> stream, Consumer<Queue<T>> consumer) Deprecated. as one may provide a queueSupplier with queues without no bounded capacity
static <T> com.google.common.base.Predicate<T>	distinctByKey(Function<? super T,?> keyExtractor) persons.stream().filter(distinctByKey(p -> p.getName());
static <T> Stream<T>	emptyStream() Deprecated.
static <T> IntStream	indexesOf(List<T> list, com.google.common.base.Predicate<T> predicate)
static <T> OptionalInt	indexOf(List<T> list, com.google.common.base.Predicate<T> predicate) Justfor the sake of the example
static <T> Stream<T>	singleton(T item)
static <T,K,U,M extends Map<K,U>> Collector<T,?,M>	toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, Supplier<M> mapSupplier) http://stackoverflow.com/questions/31004899/java-8-collectors-tomap-sortedmap
static <T> Stream<T>	toStream(Iterable<T> iterable) Deprecated.
static <T> Stream<T>	toStream(Iterator<T> iterator) Deprecated.

Methods inherited from class java.lang.Object

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

Field Detail

LOGGER

protected static final org.slf4j.Logger LOGGER

Constructor Detail

ApexStreamHelper

protected ApexStreamHelper()

Method Detail

toStream

@Deprecated
public static <T> Stream<T> toStream(Iterator<T> iterator)

Deprecated.

toStream

@Deprecated
public static <T> Stream<T> toStream(Iterable<T> iterable)

Deprecated.

The safer way to produce a Stream: not parallel. Typically because ActivePivot re-use Object[] or IRecordReader while traversing an ICursor

Parameters:

iterable -

Returns:

singleton

public static <T> Stream<T> singleton(T item)

indexOf

@Beta
public static <T> OptionalInt indexOf(List<T> list,
                                            com.google.common.base.Predicate<T> predicate)

Justfor the sake of the example

Parameters:

list -

predicate -

Returns:

indexesOf

@Beta
public static <T> IntStream indexesOf(List<T> list,
                                            com.google.common.base.Predicate<T> predicate)

consumeByPartition

@Beta
public static <T> long consumeByPartition(Stream<T> stream,
                                                Consumer<Queue<T>> consumer,
                                                int partitionSize)

Enable consuming a stream by blocks of size controlled by the Queue

Parameters:

queueSupplier - we may need multiple queues if the stream is parallel

stream - the stream to process

consumer - the operation to apply on each partition, which size is controlled by the capacity of the queue

Returns:

how many entries have been processed

consumeByPartition

@Beta
 @Deprecated
public static <T> long consumeByPartition(Supplier<? extends BlockingQueue<T>> queueSupplier,
                                                             Stream<T> stream,
                                                             Consumer<Queue<T>> consumer)

Deprecated. as one may provide a queueSupplier with queues without no bounded capacity

emptyStream

@Deprecated
public static <T> Stream<T> emptyStream()

Deprecated.

Prevfent the requirement for a diamond

Returns:

an empty Stream

toMap

public static <T,K,U,M extends Map<K,U>> Collector<T,?,M> toMap(Function<? super T,? extends K> keyMapper,
                                                                Function<? super T,? extends U> valueMapper,
                                                                Supplier<M> mapSupplier)

http://stackoverflow.com/questions/31004899/java-8-collectors-tomap-sortedmap

Parameters:

keyMapper -

valueMapper -

mapSupplier -

Returns:

distinctByKey

public static <T> com.google.common.base.Predicate<T> distinctByKey(Function<? super T,?> keyExtractor)

persons.stream().filter(distinctByKey(p -> p.getName());

Parameters:

keyExtractor -

Returns:

a Predicate to be used in Stream.filter It will behaves like having a distinct on given property