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 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 `Future`s, 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 duration
  Definition Classes
    concurrent
- Deadline
- DoubleMult
- Duration
- DurationConversions
- DurationDouble
- DurationInt
- DurationLong
- FiniteDuration
- IntMult
- LongMult
- fromNow
- span

c

scala.concurrent.duration

# DurationDouble 

###

#### implicit final class DurationDouble extends AnyVal with DurationConversions

Source
  package.scala

Linear Supertypes
DurationConversions, AnyVal, Any
 
Ordering

1. Alphabetic
2. By Inheritance

Inherited

1. DurationDouble
2. DurationConversions
3. AnyVal
4. Any

Implicitly

1. by any2stringadd
2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

1. Hide All
2. Show All

Visibility

1. Public
2. All

### Instance Constructors

1.  new DurationDouble(d: Double)

### 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
     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
     Any
3.  def +(other: String): String
   Implicit
     This member is added by an implicit conversion from DurationDouble to any2stringadd[DurationDouble] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (DurationDouble, B)
   Implicit
     This member is added by an implicit conversion from DurationDouble to ArrowAssoc[DurationDouble] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()
5.  final def ==(arg0: Any): Boolean

   Test two objects for equality.

   Test two objects for equality. 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
     Any
6.  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`.

7.  def day[C](c: C)(implicit ev: Classifier[C]): R
   Definition Classes
     DurationConversions
8.  def day: FiniteDuration
   Definition Classes
     DurationConversions
9.  def days[C](c: C)(implicit ev: Classifier[C]): R
   Definition Classes
     DurationConversions
10.  def days: FiniteDuration
    Definition Classes
      DurationConversions
11.  def durationIn(unit: TimeUnit): FiniteDuration
    Attributes
      protected
    Definition Classes
      DurationDouble → DurationConversions
12.  def ensuring(cond: (DurationDouble) ⇒ Boolean, msg: ⇒ Any): DurationDouble
    Implicit
      This member is added by an implicit conversion from DurationDouble to Ensuring[DurationDouble] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
13.  def ensuring(cond: (DurationDouble) ⇒ Boolean): DurationDouble
    Implicit
      This member is added by an implicit conversion from DurationDouble to Ensuring[DurationDouble] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
14.  def ensuring(cond: Boolean, msg: ⇒ Any): DurationDouble
    Implicit
      This member is added by an implicit conversion from DurationDouble to Ensuring[DurationDouble] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
15.  def ensuring(cond: Boolean): DurationDouble
    Implicit
      This member is added by an implicit conversion from DurationDouble to Ensuring[DurationDouble] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
16.  def getClass(): Class[_ <: AnyVal]

    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
      AnyVal → Any
17.  def hour[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
18.  def hour: FiniteDuration
    Definition Classes
      DurationConversions
19.  def hours[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
20.  def hours: FiniteDuration
    Definition Classes
      DurationConversions
21.  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
22.  def micro[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
23.  def micro: FiniteDuration
    Definition Classes
      DurationConversions
24.  def micros[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
25.  def micros: FiniteDuration
    Definition Classes
      DurationConversions
26.  def microsecond[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
27.  def microsecond: FiniteDuration
    Definition Classes
      DurationConversions
28.  def microseconds[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
29.  def microseconds: FiniteDuration
    Definition Classes
      DurationConversions
30.  def milli[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
31.  def milli: FiniteDuration
    Definition Classes
      DurationConversions
32.  def millis[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
33.  def millis: FiniteDuration
    Definition Classes
      DurationConversions
34.  def millisecond[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
35.  def millisecond: FiniteDuration
    Definition Classes
      DurationConversions
36.  def milliseconds[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
37.  def milliseconds: FiniteDuration
    Definition Classes
      DurationConversions
38.  def minute[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
39.  def minute: FiniteDuration
    Definition Classes
      DurationConversions
40.  def minutes[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
41.  def minutes: FiniteDuration
    Definition Classes
      DurationConversions
42.  def nano[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
43.  def nano: FiniteDuration
    Definition Classes
      DurationConversions
44.  def nanos[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
45.  def nanos: FiniteDuration
    Definition Classes
      DurationConversions
46.  def nanosecond[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
47.  def nanosecond: FiniteDuration
    Definition Classes
      DurationConversions
48.  def nanoseconds[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
49.  def nanoseconds: FiniteDuration
    Definition Classes
      DurationConversions
50.  def second[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
51.  def second: FiniteDuration
    Definition Classes
      DurationConversions
52.  def seconds[C](c: C)(implicit ev: Classifier[C]): R
    Definition Classes
      DurationConversions
53.  def seconds: FiniteDuration
    Definition Classes
      DurationConversions
54.  def toString(): String

    Returns a string representation of the object.

    Returns a string representation of the object.

    The default representation is platform dependent.

    returns

      a string representation of the object.

    Definition Classes
      Any
55.  def →[B](y: B): (DurationDouble, B)
    Implicit
      This member is added by an implicit conversion from DurationDouble to ArrowAssoc[DurationDouble] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Deprecated Value Members

1.  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 for `String.format` (@see java.lang.String.format).

   Implicit
     This member is added by an implicit conversion from DurationDouble to StringFormat[DurationDouble] performed by method StringFormat in scala.Predef.
   Definition Classes
     StringFormat
   Annotations
     @deprecated @inline()
   Deprecated

     (Since version 2.12.16) Use `formatString.format(value)` instead of `value.formatted(formatString)`, or use the `f""` string interpolator. In Java 15 and later, `formatted` resolves to the new method in String which has reversed parameters.

### Inherited from DurationConversions

### Inherited from AnyVal

### Inherited from Any

### Inherited by implicit conversion any2stringadd from DurationDouble to any2stringadd[DurationDouble]

### Inherited by implicit conversion StringFormat from DurationDouble to StringFormat[DurationDouble]

### Inherited by implicit conversion Ensuring from DurationDouble to Ensuring[DurationDouble]

### Inherited by implicit conversion ArrowAssoc from DurationDouble to ArrowAssoc[DurationDouble]

### Ungrouped