object Predef extends LowPriorityImplicits with DeprecatedPredef
The Predef
object provides definitions that are accessible in all Scala
compilation units without explicit qualification.
Commonly Used Types
Predef provides type aliases for types which are commonly used, such as the immutable collection types scala.collection.immutable.Map, scala.collection.immutable.Set, and the scala.collection.immutable.List constructors (scala.collection.immutable.:: and scala.collection.immutable.Nil).
Console Output
For basic console output, Predef
provides convenience methods print and println,
which are aliases of the methods in the object scala.Console.
Assertions
A set of assert
functions are provided for use as a way to document
and dynamically check invariants in code. Invocations of assert
can be elided
at compile time by providing the command line option -Xdisable-assertions
,
which raises -Xelide-below
above elidable.ASSERTION
, to the scalac
command.
Variants of assert
intended for use with static analysis tools are also
provided: assume
, require
and ensuring
. require
and ensuring
are
intended for use as a means of design-by-contract style specification
of pre- and post-conditions on functions, with the intention that these
specifications could be consumed by a static analysis tool. For instance,
def addNaturals(nats: List[Int]): Int = { require(nats forall (_ >= 0), "List contains negative numbers") nats.foldLeft(0)(_ + _) } ensuring(_ >= 0)
The declaration of addNaturals
states that the list of integers passed should
only contain natural numbers (i.e. non-negative), and that the result returned
will also be natural. require
is distinct from assert
in that if the
condition fails, then the caller of the function is to blame rather than a
logical error having been made within addNaturals
itself. ensuring
is a
form of assert
that declares the guarantee the function is providing with
regards to its return value.
Implicit Conversions
A number of commonly applied implicit conversions are also defined here, and in the parent type scala.LowPriorityImplicits. Implicit conversions are provided for the "widening" of numeric values, for instance, converting a Short value to a Long value as required, and to add additional higher-order functions to Array values. These are described in more detail in the documentation of scala.Array.
- Source
- Predef.scala
- Grouped
- Alphabetic
- By Inheritance
- Predef
- DeprecatedPredef
- LowPriorityImplicits
- AnyRef
- Any
- Hide All
- Show All
- Public
- All
Type Members
-
sealed abstract
class
<:<
[-From, +To] extends (From) ⇒ To with Serializable
An instance of
A <:< B
witnesses thatA
is a subtype ofB
.An instance of
A <:< B
witnesses thatA
is a subtype ofB
. Requiring an implicit argument of the typeA <:< B
encodes the generalized constraintA <: B
.- Annotations
- @implicitNotFound( msg = ... )
- Note
we need a new type constructor
<:<
and evidenceconforms
, as reusingFunction1
andidentity
leads to ambiguities in case of type errors (any2stringadd
is inferred) To constrain any abstract type T that's in scope in a method's argument list (not just the method's own type parameters) simply add an implicit argument of typeT <:< U
, whereU
is the required upper bound; or for lower-bounds, use:L <:< T
, whereL
is the required lower bound. In part contributed by Jason Zaugg.
-
sealed abstract
class
=:=
[From, To] extends (From) ⇒ To with Serializable
An instance of
A =:= B
witnesses that the typesA
andB
are equal.An instance of
A =:= B
witnesses that the typesA
andB
are equal.- Annotations
- @implicitNotFound( msg = ... )
- See also
<:<
for expressing subtyping constraints
- implicit final class ArrayCharSequence extends CharSequence
- implicit final class ArrowAssoc [A] extends AnyVal
- type Class[T] = java.lang.Class[T]
-
class
DummyImplicit
extends AnyRef
A type for which there is always an implicit value.
A type for which there is always an implicit value.
- See also
scala.Array$, method
fallbackCanBuildFrom
- implicit final class Ensuring [A] extends AnyVal
- type Function[-A, +B] = (A) ⇒ B
-
type
Manifest[T] = reflect.Manifest[T]
- Annotations
- @implicitNotFound( msg = "No Manifest available for ${T}." )
- type Map[A, +B] = collection.immutable.Map[A, B]
- type OptManifest[T] = reflect.OptManifest[T]
- implicit final class RichException extends AnyVal
- implicit final class SeqCharSequence extends CharSequence
- type Set[A] = collection.immutable.Set[A]
-
type
String = java.lang.String
The
String
type in Scala has methods that come either from the underlying Java String (see the documentation corresponding to your Java version, for example http://docs.oracle.com/javase/8/docs/api/java/lang/String.html) or are added implicitly through scala.collection.immutable.StringOps. - implicit final class StringFormat [A] extends AnyVal
- implicit final class any2stringadd [A] extends AnyVal
-
type
ClassManifest[T] = ClassTag[T]
- Annotations
- @implicitNotFound( msg = ... ) @deprecated
- Deprecated
(Since version 2.10.0) use
scala.reflect.ClassTag
instead
-
type
Pair[+A, +B] = (A, B)
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use built-in tuple syntax or Tuple2 instead
-
type
Triple[+A, +B, +C] = (A, B, C)
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use built-in tuple syntax or Tuple3 instead
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
- implicit def $conforms[A]: <:<[A, A]
-
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
-
def
???: Nothing
???
can be used for marking methods that remain to be implemented.???
can be used for marking methods that remain to be implemented.- Exceptions thrown
- implicit def Boolean2boolean(x: java.lang.Boolean): Boolean
- implicit def Byte2byte(x: java.lang.Byte): Byte
- implicit def Character2char(x: Character): Char
- implicit def Double2double(x: java.lang.Double): Double
- implicit def Float2float(x: java.lang.Float): Float
- implicit def Integer2int(x: Integer): Int
- implicit def Long2long(x: java.lang.Long): Long
- val Manifest: ManifestFactory.type
- val Map: collection.immutable.Map.type
- val NoManifest: reflect.NoManifest.type
- val Set: collection.immutable.Set.type
- implicit def Short2short(x: java.lang.Short): Short
- implicit val StringCanBuildFrom: CanBuildFrom[String, Char, String]
-
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 aClassCastException
at runtime, while the expressionList(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 typeT0
.
-
final
def
assert(assertion: Boolean, message: ⇒ Any): Unit
Tests an expression, throwing an
AssertionError
if false. -
def
assert(assertion: Boolean): Unit
Tests an expression, throwing an
AssertionError
if false. -
final
def
assume(assumption: Boolean, message: ⇒ Any): Unit
Tests an expression, throwing an
AssertionError
if false.Tests an expression, throwing an
AssertionError
if false. This method differs from assert only in the intent expressed: assert contains a predicate which needs to be proven, while assume contains an axiom for a static checker. Calls to this method will not be generated if-Xelide-below
is greater thanASSERTION
.- assumption
the expression to test
- message
a String to include in the failure message
-
def
assume(assumption: Boolean): Unit
Tests an expression, throwing an
AssertionError
if false.Tests an expression, throwing an
AssertionError
if false. This method differs from assert only in the intent expressed: assert contains a predicate which needs to be proven, while assume contains an axiom for a static checker. Calls to this method will not be generated if-Xelide-below
is greater thanASSERTION
.- assumption
the expression to test
-
implicit
def
augmentString(x: String): StringOps
- Annotations
- @inline()
- implicit def boolean2Boolean(x: Boolean): java.lang.Boolean
- implicit def booleanArrayOps(xs: Array[Boolean]): ofBoolean
-
implicit
def
booleanWrapper(x: Boolean): RichBoolean
- Definition Classes
- LowPriorityImplicits
- Annotations
- @inline()
- implicit def byte2Byte(x: Byte): java.lang.Byte
- implicit def byteArrayOps(xs: Array[Byte]): ofByte
-
implicit
def
byteWrapper(x: Byte): RichByte
We prefer the java.lang.* boxed types to these wrappers in any potential conflicts.
We prefer the java.lang.* boxed types to these wrappers in any potential conflicts. Conflicts do exist because the wrappers need to implement ScalaNumber in order to have a symmetric equals method, but that implies implementing java.lang.Number as well.
Note - these are inlined because they are value classes, but the call to xxxWrapper is not eliminated even though it does nothing. Even inlined, every call site does a no-op retrieval of Predef's MODULE$ because maybe loading Predef has side effects!
- Definition Classes
- LowPriorityImplicits
- Annotations
- @inline()
- implicit def char2Character(x: Char): Character
- implicit def charArrayOps(xs: Array[Char]): ofChar
-
implicit
def
charWrapper(c: Char): RichChar
- Definition Classes
- LowPriorityImplicits
- Annotations
- @inline()
-
def
classOf[T]: Class[T]
Retrieve the runtime representation of a class type.
Retrieve the runtime representation of a class type.
classOf[T]
is equivalent to the class literalT.class
in Java.val listClass = classOf[List[_]] // listClass is java.lang.Class[List[_]] = class scala.collection.immutable.List val mapIntString = classOf[Map[Int,String]] // mapIntString is java.lang.Class[Map[Int,String]] = interface scala.collection.immutable.Map
Example: -
def
clone(): AnyRef
Create a copy of the receiver object.
- implicit def double2Double(x: Double): java.lang.Double
- implicit def doubleArrayOps(xs: Array[Double]): ofDouble
-
implicit
def
doubleWrapper(x: Double): RichDouble
- Definition Classes
- LowPriorityImplicits
- Annotations
- @inline()
-
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: Any): Boolean
The equality method for reference types.
-
implicit
def
fallbackStringCanBuildFrom[T]: CanBuildFrom[String, T, collection.immutable.IndexedSeq[T]]
- Definition Classes
- LowPriorityImplicits
-
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. - implicit def float2Float(x: Float): java.lang.Float
- implicit def floatArrayOps(xs: Array[Float]): ofFloat
-
implicit
def
floatWrapper(x: Float): RichFloat
- Definition Classes
- LowPriorityImplicits
- Annotations
- @inline()
- implicit def genericArrayOps[T](xs: Array[T]): ArrayOps[T]
-
implicit
def
genericWrapArray[T](xs: Array[T]): WrappedArray[T]
- Definition Classes
- LowPriorityImplicits
-
final
def
getClass(): java.lang.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
-
def
hashCode(): Int
The hashCode method for reference types.
-
def
identity[A](x: A): A
- Annotations
- @inline()
-
def
implicitly[T](implicit e: T): T
- Annotations
- @inline()
- implicit def int2Integer(x: Int): Integer
- implicit def intArrayOps(xs: Array[Int]): ofInt
-
implicit
def
intWrapper(x: Int): RichInt
- Definition Classes
- LowPriorityImplicits
- Annotations
- @inline()
-
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 returnfalse
, while the expressionList(1).isInstanceOf[List[String]]
will returntrue
. 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 typeT0
;false
otherwise.
- Definition Classes
- Any
-
def
locally[T](x: T): T
- Annotations
- @inline()
- implicit def long2Long(x: Long): java.lang.Long
- implicit def longArrayOps(xs: Array[Long]): ofLong
-
implicit
def
longWrapper(x: Long): RichLong
- Definition Classes
- LowPriorityImplicits
- Annotations
- @inline()
- def manifest[T](implicit m: Manifest[T]): Manifest[T]
-
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
- 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
- Note
not specified by SLS as a member of AnyRef
- def optManifest[T](implicit m: OptManifest[T]): OptManifest[T]
-
def
print(x: Any): Unit
Prints an object to
out
using itstoString
method.Prints an object to
out
using itstoString
method.- x
the object to print; may be null.
-
def
printf(text: String, xs: Any*): Unit
Prints its arguments as a formatted string to the default output, based on a string pattern (in a fashion similar to printf in C).
Prints its arguments as a formatted string to the default output, based on a string pattern (in a fashion similar to printf in C).
The interpretation of the formatting patterns is described in java.util.Formatter.
Consider using the f interpolator as more type safe and idiomatic.
- text
the pattern for formatting the arguments.
- Exceptions thrown
java.lang.IllegalArgumentException
if there was a problem with the format string or arguments- See also
-
def
println(x: Any): Unit
Prints out an object to the default output, followed by a newline character.
Prints out an object to the default output, followed by a newline character.
- x
the object to print.
-
def
println(): Unit
Prints a newline character on the default output.
- implicit def refArrayOps[T <: AnyRef](xs: Array[T]): ofRef[T]
-
final
def
require(requirement: Boolean, message: ⇒ Any): Unit
Tests an expression, throwing an
IllegalArgumentException
if false.Tests an expression, throwing an
IllegalArgumentException
if false. This method is similar toassert
, but blames the caller of the method for violating the condition.- requirement
the expression to test
- message
a String to include in the failure message
- Annotations
- @inline()
-
def
require(requirement: Boolean): Unit
Tests an expression, throwing an
IllegalArgumentException
if false.Tests an expression, throwing an
IllegalArgumentException
if false. This method is similar toassert
, but blames the caller of the method for violating the condition.- requirement
the expression to test
- implicit def short2Short(x: Short): java.lang.Short
- implicit def shortArrayOps(xs: Array[Short]): ofShort
-
implicit
def
shortWrapper(x: Short): RichShort
- Definition Classes
- LowPriorityImplicits
- Annotations
- @inline()
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
def
toString(): java.lang.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
- implicit def tuple2ToZippedOps[T1, T2](x: (T1, T2)): Ops[T1, T2]
- implicit def tuple3ToZippedOps[T1, T2, T3](x: (T1, T2, T3)): Ops[T1, T2, T3]
-
implicit
def
unaugmentString(x: StringOps): String
- Annotations
- @inline()
- implicit def unitArrayOps(xs: Array[Unit]): ofUnit
-
implicit
def
unwrapString(ws: WrappedString): String
- Definition Classes
- LowPriorityImplicits
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
implicit
def
wrapBooleanArray(xs: Array[Boolean]): WrappedArray[Boolean]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapByteArray(xs: Array[Byte]): WrappedArray[Byte]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapCharArray(xs: Array[Char]): WrappedArray[Char]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapDoubleArray(xs: Array[Double]): WrappedArray[Double]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapFloatArray(xs: Array[Float]): WrappedArray[Float]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapIntArray(xs: Array[Int]): WrappedArray[Int]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapLongArray(xs: Array[Long]): WrappedArray[Long]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapRefArray[T <: AnyRef](xs: Array[T]): WrappedArray[T]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapShortArray(xs: Array[Short]): WrappedArray[Short]
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapString(s: String): WrappedString
- Definition Classes
- LowPriorityImplicits
-
implicit
def
wrapUnitArray(xs: Array[Unit]): WrappedArray[Unit]
- Definition Classes
- LowPriorityImplicits
- object =:= extends Serializable
- object DummyImplicit
Deprecated Value Members
-
val
ClassManifest: ClassManifestFactory.type
- Annotations
- @deprecated
- Deprecated
(Since version 2.10.0) use
scala.reflect.ClassTag
instead
-
def
any2ArrowAssoc[A](x: A): ArrowAssoc[A]
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use
ArrowAssoc
-
def
any2Ensuring[A](x: A): Ensuring[A]
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use
Ensuring
-
def
any2stringfmt(x: Any): StringFormat[Any]
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use
StringFormat
-
def
arrayToCharSequence(xs: Array[Char]): CharSequence
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use
ArrayCharSequence
-
def
classManifest[T](implicit m: ClassManifest[T]): ClassManifest[T]
- Annotations
- @deprecated
- Deprecated
(Since version 2.10.0) use scala.reflect.classTag[T] instead
-
def
conforms[A]: <:<[A, A]
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use
implicitly[T <:< U]
oridentity
instead.
-
def
exceptionWrapper(exc: scala.Throwable): RichException
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use
Throwable
directly
-
def
readBoolean(): Boolean
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readByte(): Byte
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readChar(): Char
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readDouble(): Double
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readFloat(): Float
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readInt(): Int
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readLine(text: String, args: Any*): String
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readLine(): String
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readLong(): Long
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readShort(): Short
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readf(format: String): List[Any]
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readf1(format: String): Any
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readf2(format: String): (Any, Any)
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
readf3(format: String): (Any, Any, Any)
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in
scala.io.StdIn
-
def
seqToCharSequence(xs: collection.IndexedSeq[Char]): CharSequence
- Definition Classes
- DeprecatedPredef
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use
SeqCharSequence
-
object
Pair
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use built-in tuple syntax or Tuple2 instead
-
object
Triple
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use built-in tuple syntax or Tuple3 instead
Inherited from DeprecatedPredef
Inherited from LowPriorityImplicits
Inherited from AnyRef
Inherited from Any
Utility Methods
Assertions
These methods support program verification and runtime correctness.
Console Output
These methods provide output via the console.
Type Constraints
These entities allows constraints between types to be stipulated.
Aliases
These aliases bring selected immutable types into scope without any imports.
String Conversions
Conversions to and from String and StringOps.
Implicit Classes
These implicit classes add useful extension methods to every type.
CharSequence Conversions
These implicit classes add CharSequence methods to Array[Char] and IndexedSeq[Char] instances.
Java to Scala
Implicit conversion from Java primitive wrapper types to Scala equivalents.
Scala to Java
Implicit conversion from Scala AnyVals to Java primitive wrapper types equivalents.
Array to WrappedArray
Conversions from Arrays to WrappedArrays.
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.collection.parallel.immutable
- Immutable, parallel data-structures such asParVector
,ParRange
,ParHashMap
orParHashSet
scala.collection.parallel.mutable
- Mutable, parallel data-structures such asParArray
,ParHashMap
,ParTrieMap
orParHashSet
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.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)scala.util.parsing
- Parser combinators, including an example implementation of a JSON parser (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 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
.