StreamConverters

scala.jdk.StreamConverters$

This object provides extension methods to create Java Streams that operate on Scala collections (sequentially or in parallel). For more information on Java streams, consult the documentation (https://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html).

When writing Java code, use the explicit conversion methods defined in javaapi.StreamConverters instead.

The methods asJavaSeqStream and asJavaParStream convert a collection to a Java Stream:

scala> import scala.jdk.StreamConverters._

scala> val s = (1 to 10).toList.asJavaSeqStream
s: java.util.stream.IntStream = java.util.stream.IntPipeline$Head@7b1e5e55

scala> s.map(_ * 2).filter(_ > 5).toScala(List)
res1: List[Int] = List(6, 8, 10, 12, 14, 16, 18, 20)

Note: using parallel streams in the Scala REPL causes deadlocks, see https://github.com/scala/bug/issues/9076. As a workaround, use scala -Yrepl-class-based.

scala> def isPrime(n: Int): Boolean = !(2 +: (3 to Math.sqrt(n).toInt by 2) exists (n % _ == 0))
isPrime: (n: Int)Boolean

scala> (10000 to 1000000).asJavaParStream.filter(isPrime).toScala(Vector)
res6: scala.collection.immutable.Vector[Int] = Vector(10007, 10009, 10037, 10039, ...

A Java Stream provides operations on a sequence of elements. Streams are created from Spliterators, which are similar to Iterators with the additional capability to partition off some of their elements. This partitioning, if supported by the Spliterator, is used for parallelizing Stream operations.

Scala collections have a method stepper that returns a scala.collection.Stepper for the collection, which in turn can be converted to a Spliterator for creating a Java Stream.

The asJavaSeqStream extension method is available on any Scala collection. The asJavaParStream extension method can only be invoked on collections where the return type of the stepper method is marked with the scala.collection.Stepper.EfficientSplit marker trait. This trait is added to steppers that support partitioning, and therefore efficient parallel processing.

The following extension methods are available:

Collection Type

Extension Methods

IterableOnce

asJavaSeqStream

IndexedSeq, Arrays, BitSet, Accumulator, HashMap, HashSet, Range, TreeMap, TreeSet, Vector, Strings

asJavaParStream

Map

asJavaSeqKeyStream, asJavaSeqValueStream

HashMap, TreeMap

asJavaParKeyStream, asJavaParValueStream

Stepper

asJavaSeqStream

Stepper with EfficientSplit

asJavaParStream

Strings

asJavaSeqStream, asJavaParStream, asJavaSeqCharStream, asJavaParCharStream, asJavaSeqCodePointStream, asJavaParCodePointStream

Java streams

toScala, asJavaPrimitiveStream

The asJavaPrimitiveStream method converts a Stream[Int] to an IntStream. It is the dual of the boxed method defined on primitive streams (e.g., IntStream.boxed is a Stream[Integer]).

The toScala extension methods on Java streams collects the result of a stream pipeline into a Scala collection, for example stream.toScala(List), stream.toScala(Vector). Note that transformation operations on streams are lazy (also called "intermediate"), terminal operations such as forEach, count or toScala trigger the evaluation.

Collecting a parallel stream to a collection can be performed in parallel. This is beneficial if the target collection supports efficient merging of the segments that are built in parallel. To support this use case, the Scala standard library provides the Accumulator collection. This collection supports efficient parallel construction, and it has specialized subtypes for Int, Long and Double so that primitive Java streams can be collected to a Scala collection without boxing the elements.

Attributes

Source:
StreamConverters.scala
Graph
Supertypes
class Object
trait Matchable
class Any
Self type

Members list

Concise view

Type members

Inherited classlikes

implicit class AnyArrayHasSeqParStream[A <: AnyRef](a: Array[A])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class ByteArrayHasSeqParStream(a: Array[Byte])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class CharArrayHasSeqParStream(a: Array[Char])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class DoubleStreamHasToScala(stream: DoubleStream)

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class IntArrayHasSeqParStream(a: Array[Int])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class IntStreamHasToScala(stream: IntStream)

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class IterableHasSeqStream[A](cc: IterableOnce[A])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class IterableNonGenericHasParStream[A, C <: IterableOnce[_]](c: C)(implicit ev: C <:< IterableOnce[A])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class LongArrayHasSeqParStream(a: Array[Long])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class LongStreamHasToScala(stream: LongStream)

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class MapHasParKeyValueStream[K, V, CC <: (MapOps)](cc: CC[K, V])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class MapHasSeqKeyValueStream[K, V, CC <: (MapOps)](cc: CC[K, V])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class StepperHasParStream[A](stepper: Stepper[A] & EfficientSplit)

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class StepperHasSeqStream[A](stepper: Stepper[A])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class StreamHasToScala[A](stream: Stream[A])

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any
implicit class StringHasSeqParStream(s: String)

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
Graph
Supertypes
class Object
trait Matchable
class Any

Implicits

Inherited implicits

final implicit def AnyArrayHasSeqParStream[A <: AnyRef](a: Array[A]): AnyArrayHasSeqParStream[A]

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
final implicit def IterableHasSeqStream[A](cc: IterableOnce[A]): IterableHasSeqStream[A]

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
final implicit def IterableNonGenericHasParStream[A, C <: IterableOnce[_]](c: C)(implicit ev: C <:< IterableOnce[A]): IterableNonGenericHasParStream[A, C]

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
final implicit def MapHasParKeyValueStream[K, V, CC <: (MapOps)](cc: CC[K, V]): MapHasParKeyValueStream[K, V, CC]

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
final implicit def MapHasSeqKeyValueStream[K, V, CC <: (MapOps)](cc: CC[K, V]): MapHasSeqKeyValueStream[K, V, CC]

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
final implicit def StepperHasParStream[A](stepper: Stepper[A] & EfficientSplit): StepperHasParStream[A]

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
final implicit def StepperHasSeqStream[A](stepper: Stepper[A]): StepperHasSeqStream[A]

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala
final implicit def StreamHasToScala[A](stream: Stream[A]): StreamHasToScala[A]

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala

Attributes

Inherited from:
StreamExtensions
Source:
StreamExtensions.scala