Scala Standard Library2.13.0 < 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.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
package collection
Definition Classes
scala
package compat
Definition Classes
scala
package concurrent
This package object contains primitives for concurrent and parallel programming.
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.
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.
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
Since
2.9
package util
Definition Classes
scala
#::
<:<
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AnyVal
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Boolean
Byte
Char
Console
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Double
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Enumeration
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Nothing
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scala

StringContext

Companion class StringContext

object StringContext extends java.io.Serializable

Source: StringContext.scala

Linear Supertypes

java.io.Serializable, AnyRef, Any

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StringContext
Serializable
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Type Members

class InvalidEscapeException extends IllegalArgumentException
An exception that is thrown if a string contains a backslash (\) character that does not start a valid escape sequence.

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
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.
def checkLengths(args: collection.Seq[Any], parts: Seq[String]): Unit
Checks that the length of the given argument args is one less than the number of parts supplied to the StringContext.
Checks that the length of the given argument args is one less than the number of parts supplied to the StringContext.
Exceptions thrown
IllegalArgumentException if this is not the case.
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[java.lang]
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.CloneNotSupportedException]) @native()
Note
not specified by SLS as a member of AnyRef
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: AnyRef): 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[java.lang]
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.Throwable])
Note
not specified by SLS as a member of AnyRef
final def getClass(): Class[_ <: AnyRef]
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 glob(patternChunks: Seq[String], input: String): Option[Seq[String]]
Linear time glob-matching implementation.
Linear time glob-matching implementation. Adapted from https://research.swtch.com/glob
patternChunks
The non-wildcard portions of the input pattern, separated by wildcards
input
The input you wish to match against
returns
None if there is no match, Some containing the sequence of matched wildcard strings if there is a match
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
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 processEscapes(str: String): String
Expands standard Scala escape sequences in a string.
Expands standard Scala escape sequences in a string. Escape sequences are: control: \b, \t, \n, \f, \r escape: \\, \", \'
str
A string that may contain escape sequences
returns
The string with all escape sequences expanded.
def standardInterpolator(process: (String) => String, args: collection.Seq[Any], parts: Seq[String]): String
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(classOf[java.lang.InterruptedException])
final def wait(arg0: Long, arg1: Int): Unit
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])
final def wait(arg0: Long): Unit
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException]) @native()

Deprecated Value Members

def treatEscapes(str: String): String
Expands standard Scala escape sequences in a string.
Expands standard Scala escape sequences in a string. Escape sequences are: control: \b, \t, \n, \f, \r escape: \\, \", \'
str
A string that may contain escape sequences
returns
The string with all escape sequences expanded.
Annotations
@deprecated
Deprecated
(Since version 2.13.0) use processEscapes

Packages

Package structure

Automatic imports

Guide

Common Imports

Specifying Durations

Using Futures For Non-blocking Computation

Avoid Blocking

StringContext

Companion class StringContext

object StringContext extends java.io.Serializable

Type Members

Value Members

Deprecated Value Members

Inherited from java.io.Serializable

Inherited from AnyRef

Inherited from Any

Ungrouped

Packages

Package structure

Automatic imports

Guide

Common Imports

Specifying Durations

Using Futures For Non-blocking Computation

Avoid Blocking

StringContext

Companion class StringContext

object StringContext extends java.io.Serializable

Type Members

Value Members

Deprecated Value Members

Inherited from java.io.Serializable

Inherited from AnyRef

Inherited from Any

Ungrouped

StringContext