Scala Standard Library 2.13.16 - scala.concurrent.Future
Keywords: Scala Standard Library 2.13.16 scala.concurrent.Future

Scala Standard Library2.13.16 < 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.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.collection.parallel` - Parallel collections (scala-parallel-collections.jar)
  - `scala.util.parsing` - Parser combinators (scala-parser-combinators.jar)
  - `scala.swing` - A convenient wrapper around Java's GUI framework called Swing (scala-swing.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 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 `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 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
- Await
- Awaitable
- Batchable
- BlockContext
- CanAwait
- Channel
- DelayedLazyVal
- ExecutionContext
- ExecutionContextExecutor
- ExecutionContextExecutorService
- Future
- JavaConversions
- OnCompleteRunnable
- Promise
- SyncChannel
- SyncVar

t

scala.concurrent

# Future

###
Companion object Future

#### trait Future[+T] extends Awaitable[T]

A `Future` represents a value which may or may not be currently available, but will be available at some point, or an exception if that value could not be made available.

Asynchronous computations are created by calling `Future.apply`, which yields instances of `Future`. Computations are executed using an `ExecutionContext`, which is usually supplied implicitly, and which is commonly backed by a thread pool.

    import ExecutionContext.Implicits.global
    val s = "Hello"
    val f: Future[String] = Future {
      s + " future!"
    }
    f foreach {
      msg => println(msg)
    }

Note that the `global` context is convenient but restricted: "fatal" exceptions are reported only by printing a stack trace, and the underlying thread pool may be shared by a mix of jobs. For any nontrivial application, see the caveats explained at ExecutionContext and also the overview linked below, which explains exception handling in depth.

Source
  Future.scala
See also

  Futures and Promises

Linear Supertypes
Awaitable[T], AnyRef, Any
Known Subclasses
never
Type Hierarchy
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Ordering

1. Grouped
2. Alphabetic
3. By Inheritance

Inherited

1. Future
2. Awaitable
3. AnyRef
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. Protected

### Abstract Value Members

1.  abstract def isCompleted: Boolean

   Returns whether the future had already been completed with a value or an exception.

   Returns whether the future had already been completed with a value or an exception.

   Note: using this method yields nondeterministic dataflow programs.

   returns

     `true` if the future was completed, `false` otherwise

2.  abstract def onComplete[U](f: (Try[T]) => U)(implicit executor: ExecutionContext): Unit

   When this future is completed, either through an exception, or a value, apply the provided function.

   When this future is completed, either through an exception, or a value, apply the provided function.

   If the future has already been completed, this will either be applied immediately or be scheduled asynchronously.

   Note that the returned value of `f` will be discarded.

   Since this method executes asynchronously and does not produce a return value, any non-fatal exceptions thrown will be reported to the `ExecutionContext`.

   Multiple callbacks may be registered; there is no guarantee that they will be executed in a particular order.

   The provided callback always runs in the provided implicit `ExecutionContext`, though there is no guarantee that the `execute()` method on the `ExecutionContext` will be called once per callback or that `execute()` will be called in the current thread. That is, the implementation may run multiple callbacks in a batch within a single `execute()` and it may run `execute()` either immediately or asynchronously. Completion of the Future must *happen-before* the invocation of the callback.

   U

     only used to accept any return type of the given callback function

   f

     the function to be executed when this `Future` completes

3.  abstract def ready(atMost: Duration)(implicit permit: CanAwait): Future.this.type

   Await the "completed" state of this `Awaitable`.

   Await the "completed" state of this `Awaitable`.

   This method should not be called directly; use Await.ready instead.

   atMost

     maximum wait time, which may be negative (no waiting is done), Duration.Inf for unbounded waiting, or a finite positive duration

   returns

     this `Awaitable`

   Definition Classes
     Awaitable
   Annotations
     @throws(clazz = classOf[TimeoutException]) @throws(clazz = classOf[InterruptedException])
   Exceptions thrown

     `IllegalArgumentException` if `atMost` is Duration.Undefined

     `InterruptedException` if the current thread is interrupted while waiting

     `TimeoutException` if after waiting for the specified time this `Awaitable` is still not ready

4.  abstract def result(atMost: Duration)(implicit permit: CanAwait): T

   Await and return the result (of type `T`) of this `Awaitable`.

   Await and return the result (of type `T`) of this `Awaitable`.

   This method should not be called directly; use Await.result instead.

   atMost

     maximum wait time, which may be negative (no waiting is done), Duration.Inf for unbounded waiting, or a finite positive duration

   returns

     the result value if the `Awaitable` is completed within the specific maximum wait time

   Definition Classes
     Awaitable
   Annotations
     @throws(clazz = classOf[TimeoutException]) @throws(clazz = classOf[InterruptedException])
   Exceptions thrown

     `IllegalArgumentException` if `atMost` is Duration.Undefined

     `InterruptedException` if the current thread is interrupted while waiting

     `TimeoutException` if after waiting for the specified time this `Awaitable` is still not ready

5.  abstract def transform[S](f: (Try[T]) => Try[S])(implicit executor: ExecutionContext): Future[S]

   Creates a new Future by applying the specified function to the result of this Future.

   Creates a new Future by applying the specified function to the result of this Future. If there is any non-fatal exception thrown when 'f' is applied then that exception will be propagated to the resulting future.

   S

     the type of the returned `Future`

   f

     function that transforms the result of this future

   returns

     a `Future` that will be completed with the transformed value

6.  abstract def transformWith[S](f: (Try[T]) => Future[S])(implicit executor: ExecutionContext): Future[S]

   Creates a new Future by applying the specified function, which produces a Future, to the result of this Future.

   Creates a new Future by applying the specified function, which produces a Future, to the result of this Future. If there is any non-fatal exception thrown when 'f' is applied then that exception will be propagated to the resulting future.

   S

     the type of the returned `Future`

   f

     function that transforms the result of this future

   returns

     a `Future` that will be completed with the transformed value

7.  abstract def value: Option[Try[T]]

   The current value of this `Future`.

   The current value of this `Future`.

   Note: using this method yields nondeterministic dataflow programs.

   If the future was not completed the returned value will be `None`. If the future was completed the value will be `Some(Success(t))` if it contained a valid result, or `Some(Failure(error))` if it contained an exception.

   returns

     `None` if the `Future` wasn't completed, `Some` if it was.

### Concrete 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.  def +(other: String): String
   Implicit
     This member is added by an implicit conversion from Future[T] toany2stringadd[Future[T]] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (Future[T], B)
   Implicit
     This member is added by an implicit conversion from Future[T] toArrowAssoc[Future[T]] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()
5.  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
6.  def andThen[U](pf: PartialFunction[Try[T], U])(implicit executor: ExecutionContext): Future[T]

   Applies the side-effecting function to the result of this future, and returns a new future with the result of this future.

   Applies the side-effecting function to the result of this future, and returns a new future with the result of this future.

   This method allows one to enforce that the callbacks are executed in a specified order.

   Note that if one of the chained `andThen` callbacks throws an exception, that exception is not propagated to the subsequent `andThen` callbacks. Instead, the subsequent `andThen` callbacks are given the original value of this future.

   The following example prints out `5`:

       val f = Future { 5 }
       f andThen {
         case r => throw new RuntimeException("runtime exception")
       } andThen {
         case Failure(t) => println(t)
         case Success(v) => println(v)
       }

   Since this method executes asynchronously and does not produce a return value, any non-fatal exceptions thrown will be reported to the `ExecutionContext`.

   U

     only used to accept any return type of the given `PartialFunction`

   pf

     a `PartialFunction` which will be conditionally applied to the outcome of this `Future`

   returns

     a `Future` which will be completed with the exact same outcome as this `Future` but after the `PartialFunction` has been executed.

7.  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

8.  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

9.  def collect[S](pf: PartialFunction[T, S])(implicit executor: ExecutionContext): Future[S]

   Creates a new future by mapping the value of the current future, if the given partial function is defined at that value.

   Creates a new future by mapping the value of the current future, if the given partial function is defined at that value.

   If the current future contains a value for which the partial function is defined, the new future will also hold that value. Otherwise, the resulting future will fail with a `NoSuchElementException`.

   If the current future fails, then the resulting future also fails.

   Example:

       val f = Future { -5 }
       val g = f collect {
         case x if x < 0 => -x
       }
       val h = f collect {
         case x if x > 0 => x * 2
       }
       g foreach println // Eventually prints 5
       Await.result(h, Duration.Zero) // throw a NoSuchElementException

   S

     the type of the returned `Future`

   pf

     the `PartialFunction` to apply to the successful result of this `Future`

   returns

     a `Future` holding the result of application of the `PartialFunction` or a `NoSuchElementException`

10.  def ensuring(cond: (Future[T]) => Boolean, msg: => Any): Future[T]
    Implicit
      This member is added by an implicit conversion from Future[T] toEnsuring[Future[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
11.  def ensuring(cond: (Future[T]) => Boolean): Future[T]
    Implicit
      This member is added by an implicit conversion from Future[T] toEnsuring[Future[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
12.  def ensuring(cond: Boolean, msg: => Any): Future[T]
    Implicit
      This member is added by an implicit conversion from Future[T] toEnsuring[Future[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
13.  def ensuring(cond: Boolean): Future[T]
    Implicit
      This member is added by an implicit conversion from Future[T] toEnsuring[Future[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
14.  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
15.  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
16.  def failed: Future[Throwable]

    The returned `Future` will be successfully completed with the `Throwable` of the original `Future` if the original `Future` fails.

    The returned `Future` will be successfully completed with the `Throwable` of the original `Future` if the original `Future` fails.

    If the original `Future` is successful, the returned `Future` is failed with a `NoSuchElementException`.

    This future may contain a throwable object and this means that the future failed. Futures obtained through combinators have the same exception as the future they were obtained from. The following throwable objects are not contained in the future:

    - `Error` - fatal errors are not contained within futures
    - `InterruptedException` - not contained within futures
    - all `scala.util.control.ControlThrowable` except `NonLocalReturnControl` - not contained within futures

    Instead, the future is completed with an ExecutionException that has one of the exceptions above as its cause. If a future is failed with a `scala.runtime.NonLocalReturnControl`, it is completed with a value from that throwable instead.

    returns

      a failed projection of this `Future`.

17.  def fallbackTo[U >: T](that: Future[U]): Future[U]

    Creates a new future which holds the result of this future if it was completed successfully, or, if not, the result of the `that` future if `that` is completed successfully.

    Creates a new future which holds the result of this future if it was completed successfully, or, if not, the result of the `that` future if `that` is completed successfully. If both futures are failed, the resulting future holds the throwable object of the first future.

    Using this method will not cause concurrent programs to become nondeterministic.

    Example:

        val f = Future { throw new RuntimeException("failed") }
        val g = Future { 5 }
        val h = f fallbackTo g
        h foreach println // Eventually prints 5

    U

      the type of the other `Future` and the resulting `Future`

    that

      the `Future` whose result we want to use if this `Future` fails.

    returns

      a `Future` with the successful result of this or that `Future` or the failure of this `Future` if both fail

18.  def filter(p: (T) => Boolean)(implicit executor: ExecutionContext): Future[T]

    Creates a new future by filtering the value of the current future with a predicate.

    Creates a new future by filtering the value of the current future with a predicate.

    If the current future contains a value which satisfies the predicate, the new future will also hold that value. Otherwise, the resulting future will fail with a `NoSuchElementException`.

    If the current future fails, then the resulting future also fails.

    Example:

        val f = Future { 5 }
        val g = f filter { _ % 2 == 1 }
        val h = f filter { _ % 2 == 0 }
        g foreach println // Eventually prints 5
        Await.result(h, Duration.Zero) // throw a NoSuchElementException

    p

      the predicate to apply to the successful result of this `Future`

    returns

      a `Future` which will hold the successful result of this `Future` if it matches the predicate or a `NoSuchElementException`

19.  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

20.  def flatMap[S](f: (T) => Future[S])(implicit executor: ExecutionContext): Future[S]

    Creates a new future by applying a function to the successful result of this future, and returns the result of the function as the new future.

    Creates a new future by applying a function to the successful result of this future, and returns the result of the function as the new future. If this future is completed with an exception then the new future will also contain this exception.

    Example:

        val f = Future { 5 }
        val g = Future { 3 }
        val h = for {
          x: Int <- f // returns Future(5)
          y: Int <- g // returns Future(3)
        } yield x + y

    is translated to:

        f flatMap { (x: Int) => g map { (y: Int) => x + y } }

    S

      the type of the returned `Future`

    f

      the function which will be applied to the successful result of this `Future`

    returns

      a `Future` which will be completed with the result of the application of the function

21.  def flatten[S](implicit ev: <:<[T, Future[S]]): Future[S]

    Creates a new future with one level of nesting flattened, this method is equivalent to `flatMap(identity)`.

    Creates a new future with one level of nesting flattened, this method is equivalent to `flatMap(identity)`.

    S

      the type of the returned `Future`

22.  def foreach[U](f: (T) => U)(implicit executor: ExecutionContext): Unit

    Asynchronously processes the value in the future once the value becomes available.

    Asynchronously processes the value in the future once the value becomes available.

    WARNING: Will not be called if this future is never completed or if it is completed with a failure.

    Since this method executes asynchronously and does not produce a return value, any non-fatal exceptions thrown will be reported to the `ExecutionContext`.

    U

      only used to accept any return type of the given callback function

    f

      the function which will be executed if this `Future` completes with a result, the return value of `f` will be discarded.

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.  def map[S](f: (T) => S)(implicit executor: ExecutionContext): Future[S]

    Creates a new future by applying a function to the successful result of this future.

    Creates a new future by applying a function to the successful result of this future. If this future is completed with an exception then the new future will also contain this exception.

    Example:

        val f = Future { "The future" }
        val g = f map { x: String => x + " is now!" }

    Note that a for comprehension involving a `Future` may expand to include a call to `map` and or `flatMap` and `withFilter`. See scala.concurrent.Future#flatMap for an example of such a comprehension.

    S

      the type of the returned `Future`

    f

      the function which will be applied to the successful result of this `Future`

    returns

      a `Future` which will be completed with the result of the application of the function

27.  def mapTo[S](implicit tag: ClassTag[S]): Future[S]

    Creates a new `Future[S]` which is completed with this `Future`'s result if that conforms to `S`'s erased type or a `ClassCastException` otherwise.

    Creates a new `Future[S]` which is completed with this `Future`'s result if that conforms to `S`'s erased type or a `ClassCastException` otherwise.

    S

      the type of the returned `Future`

    tag

      the `ClassTag` which will be used to cast the result of this `Future`

    returns

      a `Future` holding the casted result of this `Future` or a `ClassCastException` otherwise

28.  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
29.  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

30.  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

31.  def recover[U >: T](pf: PartialFunction[Throwable, U])(implicit executor: ExecutionContext): Future[U]

    Creates a new future that will handle any matching throwable that this future might contain.

    Creates a new future that will handle any matching throwable that this future might contain. If there is no match, or if this future contains a valid result then the new future will contain the same.

    Example:

        Future (6 / 0) recover { case e: ArithmeticException => 0 } // result: 0
        Future (6 / 0) recover { case e: NotFoundException   => 0 } // result: exception
        Future (6 / 2) recover { case e: ArithmeticException => 0 } // result: 3

    U

      the type of the returned `Future`

    pf

      the `PartialFunction` to apply if this `Future` fails

    returns

      a `Future` with the successful value of this `Future` or the result of the `PartialFunction`

32.  def recoverWith[U >: T](pf: PartialFunction[Throwable, Future[U]])(implicit executor: ExecutionContext): Future[U]

    Creates a new future that will handle any matching throwable that this future might contain by assigning it a value of another future.

    Creates a new future that will handle any matching throwable that this future might contain by assigning it a value of another future.

    If there is no match, or if this future contains a valid result then the new future will contain the same result.

    Example:

        val f = Future { Int.MaxValue }
        Future (6 / 0) recoverWith { case e: ArithmeticException => f } // result: Int.MaxValue

    U

      the type of the returned `Future`

    pf

      the `PartialFunction` to apply if this `Future` fails

    returns

      a `Future` with the successful value of this `Future` or the outcome of the `Future` returned by the `PartialFunction`

33.  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
34.  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
35.  def transform[S](s: (T) => S, f: (Throwable) => Throwable)(implicit executor: ExecutionContext): Future[S]

    Creates a new future by applying the 's' function to the successful result of this future, or the 'f' function to the failed result.

    Creates a new future by applying the 's' function to the successful result of this future, or the 'f' function to the failed result. If there is any non-fatal exception thrown when 's' or 'f' is applied, that exception will be propagated to the resulting future.

    S

      the type of the returned `Future`

    s

      function that transforms a successful result of the receiver into a successful result of the returned future

    f

      function that transforms a failure of the receiver into a failure of the returned future

    returns

      a `Future` that will be completed with the transformed value

36.  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

37.  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

38.  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

39.  final def withFilter(p: (T) => Boolean)(implicit executor: ExecutionContext): Future[T]

    Used by for-comprehensions.

40.  def zip[U](that: Future[U]): Future[(T, U)]

    Zips the values of `this` and `that` future, and creates a new future holding the tuple of their results.

    Zips the values of `this` and `that` future, and creates a new future holding the tuple of their results.

    If either input future fails, the resulting future is failed with the same throwable, without waiting for the other input future to complete.

    If the application of `f` throws a non-fatal throwable, the resulting future is failed with that throwable.

    U

      the type of the other `Future`

    that

      the other `Future`

    returns

      a `Future` with the results of both futures or the failure of the first of them that failed

41.  def zipWith[U, R](that: Future[U])(f: (T, U) => R)(implicit executor: ExecutionContext): Future[R]

    Zips the values of `this` and `that` future using a function `f`, and creates a new future holding the result.

    Zips the values of `this` and `that` future using a function `f`, and creates a new future holding the result.

    If either input future fails, the resulting future is failed with the same throwable, without waiting for the other input future to complete.

    If the application of `f` throws a non-fatal throwable, the resulting future is failed with that throwable.

    U

      the type of the other `Future`

    R

      the type of the resulting `Future`

    that

      the other `Future`

    f

      the function to apply to the results of `this` and `that`

    returns

      a `Future` with the result of the application of `f` to the results of `this` and `that`

### 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 Future[T] toStringFormat[Future[T]] 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.

2.  def →[B](y: B): (Future[T], B)
   Implicit
     This member is added by an implicit conversion from Future[T] toArrowAssoc[Future[T]] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @deprecated
   Deprecated

     (Since version 2.13.0) Use `->` instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

### Inherited from Awaitable[T]

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd fromFuture[T] to any2stringadd[Future[T]]

### Inherited by implicit conversion StringFormat fromFuture[T] to StringFormat[Future[T]]

### Inherited by implicit conversion Ensuring fromFuture[T] to Ensuring[Future[T]]

### Inherited by implicit conversion ArrowAssoc fromFuture[T] to ArrowAssoc[Future[T]]

### Callbacks

### Polling

### Transformations

### Ungrouped