Scala Standard Library2.12.20 < Back

Packages

package root
This is the documentation for the Scala standard library.
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like Int, Float, Array or Option which are accessible in all Scala compilation units without explicit qualification or imports.
Notable packages include:
- scala.collection and its sub-packages contain Scala's collections framework
  - scala.collection.immutable - Immutable, sequential data-structures such as Vector, List, Range, HashMap or HashSet
  - scala.collection.mutable - Mutable, sequential data-structures such as ArrayBuffer, StringBuilder, HashMap or HashSet
  - scala.collection.concurrent - Mutable, concurrent data-structures such as TrieMap
  - scala.collection.parallel.immutable - Immutable, parallel data-structures such as ParVector, ParRange, ParHashMap or ParHashSet
  - scala.collection.parallel.mutable - Mutable, parallel data-structures such as ParArray, ParHashMap, ParTrieMap or ParHashSet
- scala.concurrent - Primitives for concurrent programming such as Futures and Promises
- scala.io - Input and output operations
- scala.math - Basic math functions and additional numeric types like BigInt and BigDecimal
- scala.sys - Interaction with other processes and the operating system
- scala.util.matching - Regular expressions
Other packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
- scala.reflect - Scala's reflection API (scala-reflect.jar)
- scala.xml - XML parsing, manipulation, and serialization (scala-xml.jar)
- scala.swing - A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)
- scala.util.parsing - Parser combinators (scala-parser-combinators.jar)
Automatic imports
Identifiers in the scala package and the scala.Predef object are always in scope by default.
Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example, List is an alias for scala.collection.immutable.List.
Other aliases refer to classes provided by the underlying platform. For example, on the JVM, String is an alias for java.lang.String.
Definition Classes
root
package scala
Core Scala types.
Core Scala types. They are always available without an explicit import.

Definition Classes
root
package collection
Contains the base traits and objects needed to use and extend Scala's collection library.
Contains the base traits and objects needed to use and extend Scala's collection library.
Guide
A detailed guide for using the collections library is available at http://docs.scala-lang.org/overviews/collections/introduction.html. Developers looking to extend the collections library can find a description of its architecture at http://docs.scala-lang.org/overviews/core/architecture-of-scala-collections.html.
Using Collections
It is convenient to treat all collections as either a scala.collection.Traversable or scala.collection.Iterable, as these traits define the vast majority of operations on a collection.
Collections can, of course, be treated as specifically as needed, and the library is designed to ensure that the methods that transform collections will return a collection of the same type:
```
scala> val array = Array(1,2,3,4,5,6)
array: Array[Int] = Array(1, 2, 3, 4, 5, 6)

scala> array map { _.toString }
res0: Array[String] = Array(1, 2, 3, 4, 5, 6)

scala> val list = List(1,2,3,4,5,6)
list: List[Int] = List(1, 2, 3, 4, 5, 6)

scala> list map { _.toString }
res1: List[String] = List(1, 2, 3, 4, 5, 6)
```
Creating Collections
The most common way to create a collection is to use its companion object as a factory. The three most commonly used collections are scala.collection.Seq, scala.collection.immutable.Set, and scala.collection.immutable.Map. They can be used directly as shown below since their companion objects are all available as type aliases in either the scala package or in scala.Predef. New collections are created like this:
```
scala> val seq = Seq(1,2,3,4,1)
seq: Seq[Int] = List(1, 2, 3, 4, 1)

scala> val set = Set(1,2,3,4,1)
set: scala.collection.immutable.Set[Int] = Set(1, 2, 3, 4)

scala> val map = Map(1 -> "one", 2 -> "two", 3 -> "three", 2 -> "too")
map: scala.collection.immutable.Map[Int,String] = Map(1 -> one, 2 -> too, 3 -> three)
```
It is also typical to prefer the scala.collection.immutable collections over those in scala.collection.mutable; the types aliased in the scala.Predef object are the immutable versions.
Also note that the collections library was carefully designed to include several implementations of each of the three basic collection types. These implementations have specific performance characteristics which are described in the guide.
The concrete parallel collections also have specific performance characteristics which are described in the parallel collections guide
Converting to and from Java Collections
The scala.collection.JavaConverters object provides a collection of decorators that allow converting between Scala and Java collections using asScala and asJava methods.
Definition Classes
scala
package parallel
Package object for parallel collections.
Package object for parallel collections.

Definition Classes
collection
package immutable

Definition Classes
parallel
package mutable

Definition Classes
parallel
AdaptiveWorkStealingForkJoinTasks
AdaptiveWorkStealingTasks
AdaptiveWorkStealingThreadPoolTasks
CollectionsHaveToParArray
Combiner
CombinerFactory
CompositeThrowable
ExecutionContextTaskSupport
ExecutionContextTasks
FactoryOps
ForkJoinTaskSupport
ForkJoinTasks
FutureThreadPoolTasks
HavingForkJoinPool
IterableSplitter
ParIterable
ParIterableLike
ParMap
ParMapLike
ParSeq
ParSeqLike
ParSet
ParSetLike
PreciseSplitter
SeqSplitter
Splitter
Task
TaskSupport
Tasks
ThreadPoolTaskSupport
ThreadPoolTasks
ThrowableOps
TraversableOps

scala.collection.parallel

ParSet

Companion trait ParSet

object ParSet extends ParSetFactory[ParSet]

Source: ParSet.scala

Linear Supertypes

ParSetFactory[ParSet], GenericParCompanion[ParSet], GenSetFactory[ParSet], GenericCompanion[ParSet], AnyRef, Any

Ordering

Alphabetic
By Inheritance

Inherited

ParSet
ParSetFactory
GenericParCompanion
GenSetFactory
GenericCompanion
AnyRef
Any

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Visibility

Public
All

Type Members

class GenericCanCombineFrom[A] extends CanCombineFrom[CC[_], A, CC[A]]

Definition Classes
ParSetFactory
type Coll = ParSet[_]
The underlying collection type with unknown element type
The underlying collection type with unknown element type

Attributes
protected[this]
Definition Classes
GenericCompanion

Value Members

final def !=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
returns
true if !(this == that), false otherwise.

Definition Classes
AnyRef → Any
final def ##(): Int
Equivalent to x.hashCode except for boxed numeric types and null.
Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.
returns
a hash value consistent with ==

Definition Classes
AnyRef → Any
final def ==(arg0: Any): Boolean
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
returns
true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
AnyRef → Any
def apply[A](elems: A*): ParSet[A]
Creates a collection with the specified elements.
Creates a collection with the specified elements.
A
the type of the collection's elements
elems
the elements of the created collection
returns
a new collection with elements elems

Definition Classes
GenericCompanion
final def asInstanceOf[T0]: T0
Cast the receiver object to be of type T0.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.
returns
the receiver object.

Definition Classes
Any
Exceptions thrown
ClassCastException if the receiver object is not an instance of the erasure of type T0.
implicit def canBuildFrom[T]: CanCombineFrom[Coll, T, ParSet[T]]
def clone(): AnyRef
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the clone method is platform dependent.
returns
a copy of the receiver object.

Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws( ... ) @native()
Note
not specified by SLS as a member of AnyRef
def empty[A]: ParSet[A]
An empty collection of type CC[A]
An empty collection of type CC[A]
A
the type of the collection's elements

Definition Classes
GenericCompanion
final def eq(arg0: AnyRef): Boolean
Tests whether the argument (that) is a reference to the receiver object (this).
Tests whether the argument (that) is a reference to the receiver object (this).
The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:
- It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
- For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
- null.eq(null) returns true.
When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
returns
true if the argument is a reference to the receiver object; false otherwise.

Definition Classes
AnyRef
def equals(arg0: Any): Boolean
The equality method for reference types.
The equality method for reference types. Default implementation delegates to eq.
See also equals in scala.Any.
returns
true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
AnyRef → Any
def finalize(): Unit
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
Note
not specified by SLS as a member of AnyRef
final def getClass(): Class[_]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
returns
a class object corresponding to the runtime type of the receiver.

Definition Classes
AnyRef → Any
Annotations
@native()
def hashCode(): Int
The hashCode method for reference types.
The hashCode method for reference types. See hashCode in scala.Any.
returns
the hash code value for this object.

Definition Classes
AnyRef → Any
Annotations
@native()
final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is T0.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.
returns
true if the receiver object is an instance of erasure of type T0; false otherwise.

Definition Classes
Any
final def ne(arg0: AnyRef): Boolean
Equivalent to !(this eq that).
Equivalent to !(this eq that).
returns
true if the argument is not a reference to the receiver object; false otherwise.

Definition Classes
AnyRef
def newBuilder[A]: Combiner[A, ParSet[A]]
The default builder for ParIterable objects.
The default builder for ParIterable objects.

Definition Classes
ParSetFactory → GenericParCompanion → GenSetFactory → GenericCompanion
def newCombiner[T]: Combiner[T, ParSet[T]]
The parallel builder for ParIterable objects.
The parallel builder for ParIterable objects.

Definition Classes
ParSet → ParSetFactory → GenericParCompanion
final def notify(): Unit
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.

Definition Classes
AnyRef
Annotations
@native()
Note
not specified by SLS as a member of AnyRef
final def notifyAll(): Unit
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.

Definition Classes
AnyRef
Annotations
@native()
Note
not specified by SLS as a member of AnyRef
def setCanBuildFrom[A]: CanBuildFrom[ParSet[_], A, ParSet[A]]
The standard CanBuildFrom instance for Set objects.
The standard CanBuildFrom instance for Set objects.

Definition Classes
GenSetFactory
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def toString(): String
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
returns
a String representation of the object.

Definition Classes
AnyRef → Any
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws( ... ) @native()

Packages

Package structure

Automatic imports

Guide

Using Collections

Creating Collections

Converting to and from Java Collections

ParSet

Companion trait ParSet

object ParSet extends ParSetFactory[ParSet]

Type Members

Value Members

Inherited from ParSetFactory[ParSet]

Inherited from GenericParCompanion[ParSet]

Inherited from GenSetFactory[ParSet]

Inherited from GenericCompanion[ParSet]

Inherited from AnyRef

Inherited from Any

Ungrouped

Packages

Package structure

Automatic imports

Guide

Using Collections

Creating Collections

Converting to and from Java Collections

ParSet 

Companion trait ParSet

object ParSet extends ParSetFactory[ParSet]

Type Members

Value Members

Inherited from ParSetFactory[ParSet]

Inherited from GenericParCompanion[ParSet]

Inherited from GenSetFactory[ParSet]

Inherited from GenericCompanion[ParSet]

Inherited from AnyRef

Inherited from Any

Ungrouped

ParSet