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:

    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 https://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 words = Files.readAllLines("/etc/dictionaries-common/words").asScala
      words.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

case class Deadline extends Ordered[Deadline] with Product with Serializable

This class stores a deadline, as obtained via Deadline.now or the duration DSL:

import scala.concurrent.duration._
3.seconds.fromNow

Its main purpose is to manage repeated attempts to achieve something (like awaiting a condition) by offering the methods hasTimeLeft and timeLeft. All durations are measured according to System.nanoTime; this does not take into account changes to the system clock (such as leap seconds).

Source
Deadline.scala
Type Hierarchy
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. Deadline
  2. Serializable
  3. Product
  4. Equals
  5. Ordered
  6. Comparable
  7. AnyRef
  8. Any
Implicitly
  1. by orderingToOrdered
  2. by any2stringadd
  3. by StringFormat
  4. by Ensuring
  5. by ArrowAssoc
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. Protected

Value Members

  1. def +(other: FiniteDuration): Deadline

    Return a deadline advanced (i.e., moved into the future) by the given duration.

  2. def -(other: Deadline): FiniteDuration

    Calculate time difference between this and the other deadline, where the result is directed (i.e., may be negative).

  3. def -(other: FiniteDuration): Deadline

    Return a deadline moved backwards (i.e., towards the past) by the given duration.

  4. def <(that: Deadline): Boolean

    Returns true if this is less than that

    Returns true if this is less than that

    Definition Classes
    Ordered
  5. def <=(that: Deadline): Boolean

    Returns true if this is less than or equal to that.

    Returns true if this is less than or equal to that.

    Definition Classes
    Ordered
  6. def >(that: Deadline): Boolean

    Returns true if this is greater than that.

    Returns true if this is greater than that.

    Definition Classes
    Ordered
  7. def >=(that: Deadline): Boolean

    Returns true if this is greater than or equal to that.

    Returns true if this is greater than or equal to that.

    Definition Classes
    Ordered
  8. def compare(other: Deadline): Int

    The natural ordering for deadline is determined by the natural order of the underlying (finite) duration.

    The natural ordering for deadline is determined by the natural order of the underlying (finite) duration.

    Definition Classes
    DeadlineOrdered
  9. def compareTo(that: Deadline): Int

    Result of comparing this with operand that.

    Result of comparing this with operand that.

    Definition Classes
    Ordered → Comparable
  10. def hasTimeLeft(): Boolean

    Determine whether the deadline still lies in the future at the point where this method is called.

    Determine whether the deadline still lies in the future at the point where this method is called.

    Note that on some systems this operation is costly because it entails a system call. Check System.nanoTime for your platform.

  11. def isOverdue(): Boolean

    Determine whether the deadline lies in the past at the point where this method is called.

    Determine whether the deadline lies in the past at the point where this method is called.

    Note that on some systems this operation is costly because it entails a system call. Check System.nanoTime for your platform.

  12. def productElementNames: Iterator[String]

    An iterator over the names of all the elements of this product.

    An iterator over the names of all the elements of this product.

    Definition Classes
    Product
  13. val time: FiniteDuration
  14. def timeLeft: FiniteDuration

    Calculate time difference between this duration and now; the result is negative if the deadline has passed.

    Calculate time difference between this duration and now; the result is negative if the deadline has passed.

    Note that on some systems this operation is costly because it entails a system call. Check System.nanoTime for your platform.

Shadowed Implicit Value Members

  1. def <(that: Deadline): Boolean

    Returns true if this is less than that

    Returns true if this is less than that

    Implicit
    This member is added by an implicit conversion from Deadline tomath.Ordered[Deadline] performed by method orderingToOrdered in scala.math.Ordered.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (deadline: math.Ordered[Deadline]).<(that)
    Definition Classes
    Ordered
  2. def <=(that: Deadline): Boolean

    Returns true if this is less than or equal to that.

    Returns true if this is less than or equal to that.

    Implicit
    This member is added by an implicit conversion from Deadline tomath.Ordered[Deadline] performed by method orderingToOrdered in scala.math.Ordered.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (deadline: math.Ordered[Deadline]).<=(that)
    Definition Classes
    Ordered
  3. def >(that: Deadline): Boolean

    Returns true if this is greater than that.

    Returns true if this is greater than that.

    Implicit
    This member is added by an implicit conversion from Deadline tomath.Ordered[Deadline] performed by method orderingToOrdered in scala.math.Ordered.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (deadline: math.Ordered[Deadline]).>(that)
    Definition Classes
    Ordered
  4. def >=(that: Deadline): Boolean

    Returns true if this is greater than or equal to that.

    Returns true if this is greater than or equal to that.

    Implicit
    This member is added by an implicit conversion from Deadline tomath.Ordered[Deadline] performed by method orderingToOrdered in scala.math.Ordered.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (deadline: math.Ordered[Deadline]).>=(that)
    Definition Classes
    Ordered
  5. def compare(that: Deadline): Int

    Result of comparing this with operand that.

    Result of comparing this with operand that.

    Implement this method to determine how instances of A will be sorted.

    Returns x where:

    • x < 0 when this < that
    • x == 0 when this == that
    • x > 0 when this > that
    Implicit
    This member is added by an implicit conversion from Deadline tomath.Ordered[Deadline] performed by method orderingToOrdered in scala.math.Ordered.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (deadline: math.Ordered[Deadline]).compare(that)
    Definition Classes
    Ordered
  6. def compareTo(that: Deadline): Int

    Result of comparing this with operand that.

    Result of comparing this with operand that.

    Implicit
    This member is added by an implicit conversion from Deadline tomath.Ordered[Deadline] performed by method orderingToOrdered in scala.math.Ordered.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (deadline: math.Ordered[Deadline]).compareTo(that)
    Definition Classes
    Ordered → Comparable