Package org.hortonmachine.gears.utils

Class StreamUtils

java.lang.Object

org.hortonmachine.gears.utils.StreamUtils

public class StreamUtils
extends Object

Utilities for Streams. This more a streams j8 documentation then something to really use.

Use .peek(e->sysout) to debug without interference on the stream's items

Use primitive streams were possible: IntStream, LongStream, DoubleStream.

Intermediate Methods, which produce again streams:

• map
• filter
• distinct
• sorted
• peek
• limit
• substream
• parallel
• sequential
• unordered

Terminate Methods, after which the stream is consumed and no more operations can be performed on it:

• forEach
• forEachOrdered
• toArray
• reduce
• collect
• min
• max
• count
• anyMatch
• allMatch
• noneMatch
• findFirst
• findAny
• iterator

Short-circuit Methods, that stop stream processing once conditions are satisfied.

• anyMatch
• allMatch
• noneMatch
• findFirst
• findAny
• limit
• substream

Author:

Antonello Andrea (www.hydrologis.com)

Constructor Summary

Constructors

Constructor	Description
StreamUtils()

Method Summary

Modifier and Type	Method	Description
static long	countStrings(Stream<String> stream, boolean distinct, boolean ignoreCase)
static <T> Stream<T>	distinct(Stream<T> stream)
static <T> Stream<T>	findAll(Stream<T> stream, Predicate<T> predicate)
static <T> T	findAny(Stream<T> stream, Predicate<T> predicate)	Find an element in the stream.
static <T> Stream<T>	fromArray(T[] array)
static <T> Stream<T>	fromList(List<T> list)
static <T> Stream<T>	fromListParallel(List<T> list)
static <T> Stream<T>	fromSupplier(Supplier<T> supplier)
static String	getString(Stream<Object> stream, String separator, String prefix, String suffix)
static <T,R> void	printLongStats(Stream<T> stream, ToLongFunction<T> summarizingFunction)
static <T> List<T>	toList(Stream<T> stream)
static <T,K,V> Map<K,V>	toMap(Stream<T> stream, Function<T,K> keySupplier, Function<T,V> valueSupplier)	Collect stream to map.
static <T,K,R> Map<R,List<T>>	toMapGroupBy(Stream<T> stream, Function<T,R> groupingFunction)	Collect a map by grouping based on the object's field.
static <T> Map<Boolean,List<T>>	toMapPartition(Stream<T> stream, Predicate<T> predicate)	Split a stream into a map with true and false.
static <T,K> Map<K,T>	toMapWithToStringValue(Stream<T> stream, Function<T,K> keySupplier)
static <T> Set<T>	toSet(Stream<T> stream)
static <T> TreeSet<T>	toTreeSet(Stream<T> stream)

Methods inherited from class java.lang.Object

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

Constructor Detail

StreamUtils

public StreamUtils()

Method Detail

fromArray

public static <T> Stream<T> fromArray(T[] array)

fromList

public static <T> Stream<T> fromList(List<T> list)

fromListParallel

public static <T> Stream<T> fromListParallel(List<T> list)

fromSupplier

public static <T> Stream<T> fromSupplier(Supplier<T> supplier)

distinct

public static <T> Stream<T> distinct(Stream<T> stream)

countStrings

public static long countStrings(Stream<String> stream,
                                boolean distinct,
                                boolean ignoreCase)

getString

public static String getString(Stream<Object> stream,
                               String separator,
                               String prefix,
                               String suffix)

toList

public static <T> List<T> toList(Stream<T> stream)

toSet

public static <T> Set<T> toSet(Stream<T> stream)

toTreeSet

public static <T> TreeSet<T> toTreeSet(Stream<T> stream)

toMap

public static <T,K,V> Map<K,V> toMap(Stream<T> stream,
                                                       Function<T,K> keySupplier,
                                                       Function<T,V> valueSupplier)

Collect stream to map.

Parameters:

stream - the stream to convert.

keySupplier - the supplier for the key, ex. Object::getId()

valueSupplier - the value supplier, ex. Object::getValue()

Returns:

the map.

toMapWithToStringValue

public static <T,K> Map<K,T> toMapWithToStringValue(Stream<T> stream,
                                                                Function<T,K> keySupplier)

toMapGroupBy

public static <T,K,R> Map<R,List<T>> toMapGroupBy(Stream<T> stream,
                                                                    Function<T,R> groupingFunction)

Collect a map by grouping based on the object's field.

Parameters:

stream - the stream to collect.

groupingFunction - the function supplying the grouping field, ex. Object::getField()

Returns:

the map of lists.

toMapPartition

public static <T> Map<Boolean,List<T>> toMapPartition(Stream<T> stream,
                                                            Predicate<T> predicate)

Split a stream into a map with true and false.

Parameters:

stream - the stream to collect.

predicate - the predicate to use to define true or false, ex. e->e.getValue().equals("test")

Returns:

the map of lists.

printLongStats

public static <T,R> void printLongStats(Stream<T> stream,
                                              ToLongFunction<T> summarizingFunction)

findAny

public static <T> T findAny(Stream<T> stream,
                            Predicate<T> predicate)

Find an element in the stream.

Parameters:

stream - the stream to check. This should be parallel.

predicate - the predicate to use.

Returns:

the element or null.

findAll

public static <T> Stream<T> findAll(Stream<T> stream,
                                    Predicate<T> predicate)