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:

    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 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 duration
    Definition Classes
    concurrent
  • object Duration extends Serializable
    Definition Classes
    duration
  • DurationIsOrdered
  • Infinite
o

scala.concurrent.duration.Duration

DurationIsOrdered

implicit object DurationIsOrdered extends Ordering[Duration]

The natural ordering of durations matches the natural ordering for Double, including non-finite values.

Source
Duration.scala
Linear Supertypes
math.Ordering[Duration], math.PartialOrdering[Duration], math.Equiv[Duration], Serializable, java.io.Serializable, Comparator[Duration], AnyRef, Any
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. DurationIsOrdered
  2. Ordering
  3. PartialOrdering
  4. Equiv
  5. Serializable
  6. Serializable
  7. Comparator
  8. AnyRef
  9. Any
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. All

Type Members

  1. class Ops extends AnyRef

    This inner class defines comparison operators available for T.

    This inner class defines comparison operators available for T.

    Definition Classes
    Ordering

Value Members

  1. def compare(a: Duration, b: Duration): Int

    Returns an integer whose sign communicates how x compares to y.

    Returns an integer whose sign communicates how x compares to y.

    The result sign has the following meaning:

    • negative if x < y
    • positive if x > y
    • zero otherwise (if x == y)
    Definition Classes
    DurationIsOrdered → Ordering → Comparator
  2. def equiv(x: Duration, y: Duration): Boolean

    Return true if x == y in the ordering.

    Return true if x == y in the ordering.

    Definition Classes
    Ordering → PartialOrdering → Equiv
  3. def gt(x: Duration, y: Duration): Boolean

    Return true if x > y in the ordering.

    Return true if x > y in the ordering.

    Definition Classes
    Ordering → PartialOrdering
  4. def gteq(x: Duration, y: Duration): Boolean

    Return true if x >= y in the ordering.

    Return true if x >= y in the ordering.

    Definition Classes
    Ordering → PartialOrdering
  5. def lt(x: Duration, y: Duration): Boolean

    Return true if x < y in the ordering.

    Return true if x < y in the ordering.

    Definition Classes
    Ordering → PartialOrdering
  6. def lteq(x: Duration, y: Duration): Boolean

    Return true if x <= y in the ordering.

    Return true if x <= y in the ordering.

    Definition Classes
    Ordering → PartialOrdering
  7. def max(x: Duration, y: Duration): Duration

    Return x if x >= y, otherwise y.

    Return x if x >= y, otherwise y.

    Definition Classes
    Ordering
  8. def min(x: Duration, y: Duration): Duration

    Return x if x <= y, otherwise y.

    Return x if x <= y, otherwise y.

    Definition Classes
    Ordering
  9. implicit def mkOrderingOps(lhs: Duration): Ops

    This implicit method augments T with the comparison operators defined in scala.math.Ordering.Ops.

    This implicit method augments T with the comparison operators defined in scala.math.Ordering.Ops.

    Definition Classes
    Ordering
  10. def on[U](f: (U) ⇒ Duration): math.Ordering[U]

    Given f, a function from U into T, creates an Ordering[U] whose compare function is equivalent to:

    Given f, a function from U into T, creates an Ordering[U] whose compare function is equivalent to:

    def compare(x:U, y:U) = Ordering[T].compare(f(x), f(y))
    Definition Classes
    Ordering
  11. def reverse: math.Ordering[Duration]

    Return the opposite ordering of this one.

    Return the opposite ordering of this one.

    Definition Classes
    Ordering → PartialOrdering
  12. def reversed(): Comparator[Duration]
    Definition Classes
    Comparator
  13. def thenComparing[U <: Comparable[_ >: U]](arg0: java.util.function.Function[_ >: Duration, _ <: U]): Comparator[Duration]
    Definition Classes
    Comparator
  14. def thenComparing[U](arg0: java.util.function.Function[_ >: Duration, _ <: U], arg1: Comparator[_ >: U]): Comparator[Duration]
    Definition Classes
    Comparator
  15. def thenComparing(arg0: Comparator[_ >: Duration]): Comparator[Duration]
    Definition Classes
    Comparator
  16. def thenComparingDouble(arg0: ToDoubleFunction[_ >: Duration]): Comparator[Duration]
    Definition Classes
    Comparator
  17. def thenComparingInt(arg0: ToIntFunction[_ >: Duration]): Comparator[Duration]
    Definition Classes
    Comparator
  18. def thenComparingLong(arg0: ToLongFunction[_ >: Duration]): Comparator[Duration]
    Definition Classes
    Comparator
  19. def tryCompare(x: Duration, y: Duration): Some[Int]

    Returns whether a comparison between x and y is defined, and if so the result of compare(x, y).

    Returns whether a comparison between x and y is defined, and if so the result of compare(x, y).

    Definition Classes
    Ordering → PartialOrdering