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

object Duration extends java.io.Serializable

Ordering
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Inherited
  1. Duration
  2. Serializable
  3. AnyRef
  4. Any
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Visibility
  1. Public
  2. Protected

Type Members

  1. sealed abstract class Infinite extends Duration

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
    AnyRef → 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
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    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
    AnyRef → Any
  4. val Inf: Infinite

    Infinite duration: greater than any other (apart from Undefined) and not equal to any other but itself.

    Infinite duration: greater than any other (apart from Undefined) and not equal to any other but itself. This value closely corresponds to Double.PositiveInfinity, matching its semantics in arithmetic operations.

  5. val MinusInf: Infinite

    Infinite duration: less than any other and not equal to any other but itself.

    Infinite duration: less than any other and not equal to any other but itself. This value closely corresponds to Double.NegativeInfinity, matching its semantics in arithmetic operations.

  6. val Undefined: Infinite

    The Undefined value corresponds closely to Double.NaN:

    The Undefined value corresponds closely to Double.NaN:

    • it is the result of otherwise invalid operations
    • it does not equal itself (according to equals())
    • it compares greater than any other Duration apart from itself (for which compare returns 0)

    The particular comparison semantics mirror those of Double.NaN.

    Use eq when checking an input of a method against this value.

  7. val Zero: FiniteDuration

    Preconstructed value of 0.days.

  8. def apply(s: String): Duration

    Parse String into Duration.

    Parse String into Duration. Format is "<length><unit>", where whitespace is allowed before, between and after the parts. Infinities are designated by "Inf", "PlusInf", "+Inf", "Duration.Inf" and "-Inf", "MinusInf" or "Duration.MinusInf". Undefined is designated by "Duration.Undefined".

    Exceptions thrown

    NumberFormatException if format is not parsable

  9. def apply(length: Long, unit: String): FiniteDuration

    Construct a finite duration from the given length and time unit, where the latter is looked up in a list of string representation.

    Construct a finite duration from the given length and time unit, where the latter is looked up in a list of string representation. Valid choices are:

    d, day, h, hr, hour, m, min, minute, s, sec, second, ms, milli, millisecond, µs, micro, microsecond, ns, nano, nanosecond and their pluralized forms (for every but the first mentioned form of each unit, i.e. no "ds", but "days").

  10. def apply(length: Long, unit: TimeUnit): FiniteDuration

    Construct a finite duration from the given length and time unit.

    Construct a finite duration from the given length and time unit. The unit given is retained throughout calculations as long as possible, so that it can be retrieved later.

  11. def apply(length: Double, unit: TimeUnit): Duration

    Construct a Duration from the given length and unit.

    Construct a Duration from the given length and unit. Observe that nanosecond precision may be lost if

    • the unit is NANOSECONDS
    • and the length has an absolute value greater than 2^53

    Infinite inputs (and NaN) are converted into Duration.Inf, Duration.MinusInf and Duration.Undefined, respectively.

    Exceptions thrown

    IllegalArgumentException if the length was finite but the resulting duration cannot be expressed as a FiniteDuration

  12. 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 of T0, 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 when T0 is a primitive type. When T0 is primitive, asInstanceOf may insert a conversion instead of a type test. If your intent is to convert, use a toT 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 of T0, if that can be checked on this platform

  13. 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.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  14. def create(s: String): Duration

    Parse String into Duration.

    Parse String into Duration. Format is "<length><unit>", where whitespace is allowed before, between and after the parts. Infinities are designated by "Inf", "PlusInf", "+Inf" and "-Inf" or "MinusInf".

    Exceptions thrown

    NumberFormatException if format is not parsable

  15. def create(length: Long, unit: String): FiniteDuration

    Construct a finite duration from the given length and time unit, where the latter is looked up in a list of string representation.

    Construct a finite duration from the given length and time unit, where the latter is looked up in a list of string representation. Valid choices are:

    d, day, h, hour, min, minute, s, sec, second, ms, milli, millisecond, µs, micro, microsecond, ns, nano, nanosecond and their pluralized forms (for every but the first mentioned form of each unit, i.e. no "ds", but "days").

  16. def create(length: Double, unit: TimeUnit): Duration

    Construct a Duration from the given length and unit.

    Construct a Duration from the given length and unit. Observe that nanosecond precision may be lost if

    • the unit is NANOSECONDS
    • and the length has an absolute value greater than 2^53

    Infinite inputs (and NaN) are converted into Duration.Inf, Duration.MinusInf and Duration.Undefined, respectively.

    Exceptions thrown

    IllegalArgumentException if the length was finite but the resulting duration cannot be expressed as a FiniteDuration

  17. def create(length: Long, unit: TimeUnit): FiniteDuration

    Construct a finite duration from the given length and time unit.

    Construct a finite duration from the given length and time unit. The unit given is retained throughout calculations as long as possible, so that it can be retrieved later.

  18. 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 of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode 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
  19. def equals(arg0: AnyRef): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to eq.

    See also equals in scala.Any.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  20. 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 between finalize 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

  21. def fromNanos(nanos: Long): FiniteDuration

    Construct a finite duration from the given number of nanoseconds.

    Construct a finite duration from the given number of nanoseconds. The result will have the coarsest possible time unit which can exactly express this duration.

    Exceptions thrown

    IllegalArgumentException for Long.MinValue since that would lead to inconsistent behavior afterwards (cannot be negated)

  22. def fromNanos(nanos: Double): Duration

    Construct a possibly infinite or undefined Duration from the given number of nanoseconds.

    Construct a possibly infinite or undefined Duration from the given number of nanoseconds.

    The semantics of the resulting Duration objects matches the semantics of their Double counterparts with respect to arithmetic operations.

    Exceptions thrown

    IllegalArgumentException if the length was finite but the resulting duration cannot be expressed as a FiniteDuration

  23. final def getClass(): Class[_ <: AnyRef]

    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
    Annotations
    @native()
  24. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

    the hash code value for this object.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  25. 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 returns true if the value of the receiver object is a BigDecimal or a subtype of BigDecimal.
    • T0 is a parameterized class type, e.g. List[Int]: this method returns true if the value of the receiver object is some List[X] for any X. For example, List(1, 2, 3).isInstanceOf[List[String]] will return true.
    • T0 is some singleton type x.type or literal x: this method returns this.eq(x). For example, x.isInstanceOf[1] is equivalent to x.eq(1)
    • T0 is an intersection X with Y or X & Y: this method is equivalent to x.isInstanceOf[X] && x.isInstanceOf[Y]
    • T0 is a union X | Y: this method is equivalent to x.isInstanceOf[X] || x.isInstanceOf[Y]
    • T0 is a type parameter or an abstract type member: this method is equivalent to isInstanceOf[U] where U is T0's upper bound, Any if T0 is unbounded. For example, x.isInstanceOf[A] where A is an unbounded type parameter will return true for any value of x.

    This is exactly equivalent to the type pattern _: T0

    returns

    true if the receiver object is an instance of erasure of type T0; false otherwise.

    Definition Classes
    Any
    Note

    due to the unexpectedness of List(1, 2, 3).isInstanceOf[List[String]] returning true and x.isInstanceOf[A] where A is a type parameter or abstract member returning true, these forms issue a warning.

  26. 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
  27. 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

  28. 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

  29. final def synchronized[T0](arg0: => T0): T0

    Executes the code in body with an exclusive lock on this.

    Executes the code in body with an exclusive lock on this.

    returns

    the result of body

    Definition Classes
    AnyRef
  30. val timeUnit: Map[String, TimeUnit]
    Attributes
    protected[duration]
  31. val timeUnitName: Map[TimeUnit, String]
    Attributes
    protected[duration]
  32. def toString(): 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
  33. def unapply(d: Duration): Option[(Long, TimeUnit)]

    Extract length and time unit out of a duration, if it is finite.

  34. def unapply(s: String): Option[(Long, TimeUnit)]

    Extract length and time unit out of a string, where the format must match the description for apply(String).

    Extract length and time unit out of a string, where the format must match the description for apply(String). The extractor will not match for malformed strings or non-finite durations.

  35. final def wait(): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--.

    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

  36. final def wait(arg0: Long, arg1: Int): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-

    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

  37. final def wait(arg0: Long): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  38. implicit object DurationIsOrdered extends Ordering[Duration]

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

Inherited from java.io.Serializable

Inherited from AnyRef

Inherited from Any

Ungrouped