Packages

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.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.collection.parallel - Parallel collections (scala-parallel-collections.jar)
scala.util.parsing - Parser combinators (scala-parser-combinators.jar)
scala.swing - A convenient wrapper around Java's GUI framework called Swing (scala-swing.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 annotation

Definition Classes: scala

package beans

Definition Classes: scala

BeanProperty

BooleanBeanProperty

package collection

Definition Classes: scala

package compat

Definition Classes: scala

package concurrent

This package object contains primitives for concurrent and parallel programming.

Guide

A more detailed guide to Futures and Promises, including discussion and examples can be found at http://docs.scala-lang.org/overviews/core/futures.html.

Common Imports

When working with Futures, you will often find that importing the whole concurrent package is convenient:

import scala.concurrent._

When using things like Futures, it is often required to have an implicit ExecutionContext in scope. The general advice for these implicits are as follows.

If the code in question is a class or method definition, and no ExecutionContext is available, request one from the caller by adding an implicit parameter list:

def myMethod(myParam: MyType)(implicit ec: ExecutionContext) = …
//Or
class MyClass(myParam: MyType)(implicit ec: ExecutionContext) { … }

This allows the caller of the method, or creator of the instance of the class, to decide which ExecutionContext should be used.

For typical REPL usage and experimentation, importing the global ExecutionContext is often desired.

import scala.concurrent.ExcutionContext.Implicits.global

Specifying Durations

Operations often require a duration to be specified. A duration DSL is available to make defining these easier:

import scala.concurrent.duration._
val d: Duration = 10.seconds

Using Futures For Non-blocking Computation

Basic use of futures is easy with the factory method on Future, which executes a provided function asynchronously, handing you back a future result of that function without blocking the current thread. In order to create the Future you will need either an implicit or explicit ExecutionContext to be provided:

import scala.concurrent._
import ExecutionContext.Implicits.global  // implicit execution context

val firstZebra: Future[Int] = Future {
  val source = scala.io.Source.fromFile("/etc/dictionaries-common/words")
  source.toSeq.indexOfSlice("zebra")
}

Avoid Blocking

Although blocking is possible in order to await results (with a mandatory timeout duration):

import scala.concurrent.duration._
Await.result(firstZebra, 10.seconds)

and although this is sometimes necessary to do, in particular for testing purposes, blocking in general is discouraged when working with Futures and concurrency in order to avoid potential deadlocks and improve performance. Instead, use callbacks or combinators to remain in the future domain:

val animalRange: Future[Int] = for {
  aardvark <- firstAardvark
  zebra <- firstZebra
} yield zebra - aardvark

animalRange.onSuccess {
  case x if x > 500000 => println("It's a long way from Aardvark to Zebra")
}

Definition Classes: scala

package io

Definition Classes: scala

package jdk

Definition Classes: scala

package math

The package object scala.math contains methods for performing basic numeric operations such as elementary exponential, logarithmic, root and trigonometric functions.

All methods forward to java.lang.Math unless otherwise noted.

Definition Classes: scala
See also: java.lang.Math

package ref

Definition Classes: scala

package reflect

Definition Classes: scala

package sys

The package object scala.sys contains methods for reading and altering core aspects of the virtual machine as well as the world outside of it.

Definition Classes: scala

package util

Definition Classes: scala

scala

beans

package beans

Type Members

class BeanProperty extends Annotation with StaticAnnotation
When attached to a field, this annotation adds a setter and a getter method following the Java Bean convention.
When attached to a field, this annotation adds a setter and a getter method following the Java Bean convention. For example:
```
@BeanProperty
var status = ""
```
adds the following methods to the class:
```
def setStatus(s: String): Unit = { this.status = s }
def getStatus(): String = this.status
```
For fields of type Boolean, if you need a getter named isStatus, use the scala.beans.BooleanBeanProperty annotation instead.
Annotations
@field() @deprecatedInheritance(message = "Scheduled for being final in 2.14", since = "2.13.0")
class BooleanBeanProperty extends Annotation with StaticAnnotation
This annotation has the same functionality as scala.beans.BeanProperty, but the generated Bean getter will be named isFieldName instead of getFieldName.
This annotation has the same functionality as scala.beans.BeanProperty, but the generated Bean getter will be named isFieldName instead of getFieldName.
Annotations
@field() @deprecatedInheritance(message = "Scheduled for being final in 2.14", since = "2.13.0")

Packages

Package structure

Automatic imports

Guide

Common Imports

Specifying Durations

Using Futures For Non-blocking Computation

Avoid Blocking

beans

package beans

Type Members

Ungrouped

beans