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 concurrent

  Definition Classes

  collection

•  package convert

  Definition Classes

  collection

•  package generic

  Definition Classes

  collection

•  package immutable

  Definition Classes

  collection

•  package mutable

  Definition Classes

  collection

•  package parallel

  Package object for parallel collections.

  Package object for parallel collections.

  Definition Classes

  collection

•  package script

  Definition Classes

  collection

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Scala programming documentation. Copyright (c) 2003-2017 EPFL, with contributions from Lightbend.