abstract class Enumeration extends Serializable
Defines a finite set of values specific to the enumeration. Typically these values enumerate all possible forms something can take and provide a lightweight alternative to case classes.
Each call to a Value
method adds a new unique value to the enumeration.
To be accessible, these values are usually defined as val
members of
the enumeration.
All values in an enumeration share a common, unique type defined as the
Value
type member of the enumeration (Value
selected on the stable
identifier path of the enumeration instance).
Values SHOULD NOT be added to an enumeration after its construction; doing so makes the enumeration thread-unsafe. If values are added to an enumeration from multiple threads (in a non-synchronized fashion) after construction, the behavior of the enumeration is undefined.
- Self Type
- Enumeration
- Annotations
- @SerialVersionUID()
- Source
- Enumeration.scala
// Define a new enumeration with a type alias and work with the full set of enumerated values object WeekDay extends Enumeration { type WeekDay = Value val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value } import WeekDay._ def isWorkingDay(d: WeekDay) = ! (d == Sat || d == Sun) WeekDay.values filter isWorkingDay foreach println // output: // Mon // Tue // Wed // Thu // Fri
, // Example of adding attributes to an enumeration by extending the Enumeration.Val class object Planet extends Enumeration { protected case class PlanetVal(mass: Double, radius: Double) extends super.Val { def surfaceGravity: Double = Planet.G * mass / (radius * radius) def surfaceWeight(otherMass: Double): Double = otherMass * surfaceGravity } import scala.language.implicitConversions implicit def valueToPlanetVal(x: Value): PlanetVal = x.asInstanceOf[PlanetVal] val G: Double = 6.67300E-11 val Mercury = PlanetVal(3.303e+23, 2.4397e6) val Venus = PlanetVal(4.869e+24, 6.0518e6) val Earth = PlanetVal(5.976e+24, 6.37814e6) val Mars = PlanetVal(6.421e+23, 3.3972e6) val Jupiter = PlanetVal(1.9e+27, 7.1492e7) val Saturn = PlanetVal(5.688e+26, 6.0268e7) val Uranus = PlanetVal(8.686e+25, 2.5559e7) val Neptune = PlanetVal(1.024e+26, 2.4746e7) } println(Planet.values.filter(_.radius > 7.0e6)) // output: // Planet.ValueSet(Jupiter, Saturn, Uranus, Neptune)
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- By Inheritance
- Enumeration
- Serializable
- AnyRef
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- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
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- Public
- Protected
Instance Constructors
Type Members
- class Val extends Value with Serializable
A class implementing the scala.Enumeration.Value type.
A class implementing the scala.Enumeration.Value type. This class can be overridden to change the enumeration's naming and integer identification behaviour.
- Attributes
- protected
- Annotations
- @SerialVersionUID()
- abstract class Value extends Ordered[Value] with Serializable
The type of the enumerated values.
The type of the enumerated values.
- Annotations
- @SerialVersionUID()
- class ValueSet extends AbstractSet[Value] with SortedSet[Value] with SortedSetOps[Value, SortedSet, ValueSet] with StrictOptimizedIterableOps[Value, Set, ValueSet] with Serializable
A class for sets of values.
A class for sets of values. Iterating through this set will yield values in increasing order of their ids.
- Annotations
- @SerialVersionUID()
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 andnull
.Equivalent to
x.hashCode
except for boxed numeric types andnull
. 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. Fornull
returns a hashcode wherenull.hashCode
throws aNullPointerException
.- returns
a hash value consistent with ==
- Definition Classes
- AnyRef → Any
- def +(other: String): String
- Implicit
- This member is added by an implicit conversion from Enumeration toany2stringadd[Enumeration] performed by method any2stringadd in scala.Predef.
- Definition Classes
- any2stringadd
- def ->[B](y: B): (Enumeration, B)
- Implicit
- This member is added by an implicit conversion from Enumeration toArrowAssoc[Enumeration] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @inline()
- final def ==(arg0: Any): Boolean
The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.The expression
x == that
is equivalent toif (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 Value(i: Int, name: String): Value
Creates a fresh value, part of this enumeration, called
name
and identified by the integeri
.Creates a fresh value, part of this enumeration, called
name
and identified by the integeri
.- i
An integer that identifies this value at run-time. It must be unique amongst all values of the enumeration.
- name
A human-readable name for that value.
- returns
Fresh value with the provided identifier
i
and namename
.
- Attributes
- protected
- final def Value(name: String): Value
Creates a fresh value, part of this enumeration, called
name
.Creates a fresh value, part of this enumeration, called
name
.- name
A human-readable name for that value.
- returns
Fresh value called
name
.
- Attributes
- protected
- final def Value(i: Int): Value
Creates a fresh value, part of this enumeration, identified by the integer
i
.Creates a fresh value, part of this enumeration, identified by the integer
i
.- i
An integer that identifies this value at run-time. It must be unique amongst all values of the enumeration.
- returns
Fresh value identified by
i
.
- Attributes
- protected
- final def Value: Value
Creates a fresh value, part of this enumeration.
Creates a fresh value, part of this enumeration.
- Attributes
- protected
- final def apply(x: Int): Value
The value of this enumeration with given id
x
- final def asInstanceOf[T0]: T0
Forces the compiler to treat the receiver object as having type
T0
, even though doing so may violate type safety.Forces the compiler to treat the receiver object as having type
T0
, even though doing so may violate type safety.This method is useful when you believe you have type information the compiler doesn't, and it also isn't possible to check the type at runtime. In such situations, skipping type safety is the only option.
It is platform dependent whether
asInstanceOf
has any effect at runtime. It might do a runtime type test on the erasure ofT0
, insert a conversion (such as boxing/unboxing), fill in a default value, or do nothing at all.In particular,
asInstanceOf
is not a type test. It does **not** mean:this match { case x: T0 => x case _ => throw ClassCastException("...")
Use pattern matching or isInstanceOf for type testing instead.
Situations where
asInstanceOf
is useful:- when flow analysis fails to deduce
T0
automatically - when down-casting a type parameter or an abstract type member (which cannot be checked at runtime due to type erasure) If there is any doubt and you are able to type test instead, you should do so.
Be careful of using
asInstanceOf
whenT0
is a primitive type. WhenT0
is primitive,asInstanceOf
may insert a conversion instead of a type test. If your intent is to convert, use atoT
method (x.toChar
,x.toByte
, etc.).- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastException
if the receiver is not an instance of the erasure ofT0
, if that can be checked on this platform
- when flow analysis fails to deduce
- 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.
- def ensuring(cond: (Enumeration) => Boolean, msg: => Any): Enumeration
- Implicit
- This member is added by an implicit conversion from Enumeration toEnsuring[Enumeration] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: (Enumeration) => Boolean): Enumeration
- Implicit
- This member is added by an implicit conversion from Enumeration toEnsuring[Enumeration] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: Boolean, msg: => Any): Enumeration
- Implicit
- This member is added by an implicit conversion from Enumeration toEnsuring[Enumeration] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: Boolean): Enumeration
- Implicit
- This member is added by an implicit conversion from Enumeration toEnsuring[Enumeration] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- 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 ofAnyRef
, and has three additional properties:- It is consistent: for any non-null instances
x
andy
of typeAnyRef
, multiple invocations ofx.eq(y)
consistently returnstrue
or consistently returnsfalse
. - For any non-null instance
x
of typeAnyRef
,x.eq(null)
andnull.eq(x)
returnsfalse
. null.eq(null)
returnstrue
.
When overriding the
equals
orhashCode
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
- It is consistent: for any non-null instances
- def equals(arg0: AnyRef): Boolean
The equality method for reference types.
- 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 betweenfinalize
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[_ <: AnyRef]
Returns the runtime class representation of the object.
- def hashCode(): Int
The hashCode method for reference types.
- final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object has the same erasure as
T0
.Test whether the dynamic type of the receiver object has the same erasure as
T0
.Depending on what
T0
is, the test is done in one of the below ways:T0
is a non-parameterized class type, e.g.BigDecimal
: this method returnstrue
if the value of the receiver object is aBigDecimal
or a subtype ofBigDecimal
.T0
is a parameterized class type, e.g.List[Int]
: this method returnstrue
if the value of the receiver object is someList[X]
for anyX
. For example,List(1, 2, 3).isInstanceOf[List[String]]
will return true.T0
is some singleton typex.type
or literalx
: this method returnsthis.eq(x)
. For example,x.isInstanceOf[1]
is equivalent tox.eq(1)
T0
is an intersectionX with Y
orX & Y: this method is equivalent to
x.isInstanceOf[X] && x.isInstanceOf[Y]T0
is a unionX | Y
: this method is equivalent tox.isInstanceOf[X] || x.isInstanceOf[Y]
T0
is a type parameter or an abstract type member: this method is equivalent toisInstanceOf[U]
whereU
isT0
's upper bound,Any
ifT0
is unbounded. For example,x.isInstanceOf[A]
whereA
is an unbounded type parameter will return true for any value ofx
.
This is exactly equivalent to the type pattern
_: T0
- returns
true
if the receiver object is an instance of erasure of typeT0
;false
otherwise.
- Definition Classes
- Any
- Note
due to the unexpectedness of
List(1, 2, 3).isInstanceOf[List[String]]
returning true andx.isInstanceOf[A]
whereA
is a type parameter or abstract member returning true, these forms issue a warning.
- final def maxId: Int
The one higher than the highest integer amongst those used to identify values in this enumeration.
- 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
- var nextId: Int
The integer to use to identify the next created value.
The integer to use to identify the next created value.
- Attributes
- protected
- var nextName: Iterator[String]
The string to use to name the next created value.
The string to use to name the next created value.
- Attributes
- protected
- 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 readResolve(): AnyRef
- Attributes
- protected
- final def synchronized[T0](arg0: => T0): T0
Executes the code in
body
with an exclusive lock onthis
.Executes the code in
body
with an exclusive lock onthis
.- returns
the result of
body
- Definition Classes
- AnyRef
- def toString(): String
The name of this enumeration.
The name of this enumeration.
- returns
a String representation of the object.
- Definition Classes
- Enumeration → AnyRef → Any
- def values: ValueSet
The values of this enumeration as a set.
- final def wait(): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--.
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- Note
not specified by SLS as a member of AnyRef
- final def wait(arg0: Long, arg1: Int): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- Note
not specified by SLS as a member of AnyRef
- final def wait(arg0: Long): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.
- final def withName(s: String): Value
Return a
Value
from thisEnumeration
whose name matches the arguments
.Return a
Value
from thisEnumeration
whose name matches the arguments
. The names are determined automatically via reflection.- s
an
Enumeration
name- returns
the
Value
of thisEnumeration
if its name matchess
- Exceptions thrown
NoSuchElementException
if noValue
with a matching name is in thisEnumeration
- implicit object ValueOrdering extends Ordering[Value]
An ordering by id for values of this set
- object ValueSet extends SpecificIterableFactory[Value, ValueSet] with java.io.Serializable
A factory object for value sets
A factory object for value sets
- Annotations
- @SerialVersionUID()
Deprecated Value Members
- def formatted(fmtstr: String): String
Returns string formatted according to given
format
string.Returns string formatted according to given
format
string. Format strings are as forString.format
(@see java.lang.String.format).- Implicit
- This member is added by an implicit conversion from Enumeration toStringFormat[Enumeration] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.12.16) Use
formatString.format(value)
instead ofvalue.formatted(formatString)
, or use thef""
string interpolator. In Java 15 and later,formatted
resolves to the new method in String which has reversed parameters.
- def →[B](y: B): (Enumeration, B)
- Implicit
- This member is added by an implicit conversion from Enumeration toArrowAssoc[Enumeration] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @deprecated
- Deprecated
(Since version 2.13.0) Use
->
instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int
,Float
,Array
orOption
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 frameworkscala.collection.immutable
- Immutable, sequential data-structures such asVector
,List
,Range
,HashMap
orHashSet
scala.collection.mutable
- Mutable, sequential data-structures such asArrayBuffer
,StringBuilder
,HashMap
orHashSet
scala.collection.concurrent
- Mutable, concurrent data-structures such asTrieMap
scala.concurrent
- Primitives for concurrent programming such asFutures
andPromises
scala.io
- Input and output operationsscala.math
- Basic math functions and additional numeric types likeBigInt
andBigDecimal
scala.sys
- Interaction with other processes and the operating systemscala.util.matching
- Regular expressionsOther 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 forscala.collection.immutable.List
.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
String
is an alias forjava.lang.String
.