Scala Standard Library2.12.21 < Back
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# 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 annotation
  Definition Classes
    scala
-  package meta

  When defining a field, the Scala compiler creates up to four accessors for it: a getter, a setter, and if the field is annotated with `@BeanProperty`, a bean getter and a bean setter.

  When defining a field, the Scala compiler creates up to four accessors for it: a getter, a setter, and if the field is annotated with `@BeanProperty`, a bean getter and a bean setter.

  For instance in the following class definition

      class C(@myAnnot @BeanProperty var c: Int)

  there are six entities which can carry the annotation `@myAnnot`: the constructor parameter, the generated field and the four accessors.

  By default, annotations on (`val`-, `var`- or plain) constructor parameters end up on the parameter, not on any other entity. Annotations on fields by default only end up on the field.

  The meta-annotations in package `scala.annotation.meta` are used to control where annotations on fields and class parameters are copied. This is done by annotating either the annotation type or the annotation class with one or several of the meta-annotations in this package.

  #### Annotating the annotation type

  The target meta-annotations can be put on the annotation type when instantiating the annotation. In the following example, the annotation `@Id` will be added only to the bean getter `getX`.

      import javax.persistence.Id
      class A {
        @(Id @beanGetter) @BeanProperty val x = 0
      }

  In order to annotate the field as well, the meta-annotation `@field` would need to be added.

  The syntax can be improved using a type alias:

      object ScalaJPA {
        type Id = javax.persistence.Id @beanGetter
      }
      import ScalaJPA.Id
      class A {
        @Id @BeanProperty val x = 0
      }

  #### Annotating the annotation class

  For annotations defined in Scala, a default target can be specified in the annotation class itself, for example

      @getter
      class myAnnotation extends Annotation

  This only changes the default target for the annotation `myAnnotation`. When instantiating the annotation, the target can still be specified as described in the last section.

  Definition Classes
    annotation
-  package unchecked
  Definition Classes
    annotation
- Annotation
- ClassfileAnnotation
- StaticAnnotation
- TypeConstraint
- compileTimeOnly
- elidable
- implicitAmbiguous
- implicitNotFound
- nowarn
- showAsInfix
- strictfp
- switch
- tailrec
- unspecialized
- varargs

o

scala.annotation

# elidable 

###
Companion class elidable

#### object elidable

This useless appearing code was necessary to allow people to use named constants for the elidable annotation. This is what it takes to convince the compiler to fold the constants: otherwise when it's time to check an elision level it's staring at a tree like

    (Select(Level, Select(FINEST, Apply(intValue, Nil))))

instead of the number `300`.

Source
  elidable.scala
Since

  2.8

Linear Supertypes
AnyRef, Any
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Ordering

1. Alphabetic
2. By Inheritance

Inherited

1. elidable
2. AnyRef
3. Any

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Visibility

1. Public
2. All

### Value Members

1.  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
2.  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
3.  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
4.  final val ALL: Int(-2147483648)

   The levels `ALL` and `OFF` are confusing in this context because the sentiment being expressed when using the annotation is at cross purposes with the one being expressed via `-Xelide-below`.

   The levels `ALL` and `OFF` are confusing in this context because the sentiment being expressed when using the annotation is at cross purposes with the one being expressed via `-Xelide-below`. This confusion reaches its zenith at level `OFF`, where the annotation means never elide this method but `-Xelide-below OFF` is how you would say elide everything possible.

   With no simple remedy at hand, the issue is now at least documented, and aliases `MAXIMUM` and `MINIMUM` are offered.

5.  final val ASSERTION: Int(2000)
6.  final val CONFIG: Int(700)
7.  final val FINE: Int(500)
8.  final val FINER: Int(400)
9.  final val FINEST: Int(300)
10.  final val INFO: Int(800)
11.  final val MAXIMUM: Int(2147483647)
12.  final val MINIMUM: Int(-2147483648)
13.  final val OFF: Int(2147483647)
14.  final val SEVERE: Int(1000)
15.  final val WARNING: Int(900)
16.  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`.

17.  val byName: Map[String, Int]
18.  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

19.  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
20.  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
21.  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

22.  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()
23.  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()
24.  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
25.  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
26.  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

27.  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

28.  final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
      AnyRef
29.  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
30.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
31.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
32.  final def wait(arg0: Long): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... ) @native()

### Inherited from AnyRef

### Inherited from Any

### Ungrouped