Scala Standard Library2.12.3-1 < 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
-  package forkjoin
  Definition Classes
    concurrent
- Await
- Awaitable
- BlockContext
- CanAwait
- Channel
- DelayedLazyVal
- ExecutionContext
- ExecutionContextExecutor
- ExecutionContextExecutorService
- Future
- JavaConversions
- Lock
- OnCompleteRunnable
- Promise
- SyncChannel
- SyncVar

t

scala.concurrent

# ExecutionContextExecutorService 

###

#### trait ExecutionContextExecutorService extends ExecutionContextExecutor with ExecutorService

An ExecutionContext that is also a Java ExecutorService.

Source
  ExecutionContext.scala

Linear Supertypes
ExecutorService, ExecutionContextExecutor, Executor, ExecutionContext, AnyRef, Any
Type Hierarchy
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Ordering

1. Alphabetic
2. By Inheritance

Inherited

1. ExecutionContextExecutorService
2. ExecutorService
3. ExecutionContextExecutor
4. Executor
5. ExecutionContext
6. AnyRef
7. 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

### Abstract Value Members

1.  abstract def awaitTermination(arg0: Long, arg1: TimeUnit): Boolean
   Definition Classes
     ExecutorService
   Annotations
     @throws( ... )
2.  abstract def execute(arg0: Runnable): Unit
   Definition Classes
     Executor
3.  abstract def invokeAll[T](arg0: Collection[_ <: Callable[T]], arg1: Long, arg2: TimeUnit): java.util.List[java.util.concurrent.Future[T]]
   Definition Classes
     ExecutorService
   Annotations
     @throws( ... )
4.  abstract def invokeAll[T](arg0: Collection[_ <: Callable[T]]): java.util.List[java.util.concurrent.Future[T]]
   Definition Classes
     ExecutorService
   Annotations
     @throws( ... )
5.  abstract def invokeAny[T](arg0: Collection[_ <: Callable[T]], arg1: Long, arg2: TimeUnit): T
   Definition Classes
     ExecutorService
   Annotations
     @throws( ... ) @throws( ... ) @throws( ... )
6.  abstract def invokeAny[T](arg0: Collection[_ <: Callable[T]]): T
   Definition Classes
     ExecutorService
   Annotations
     @throws( ... ) @throws( ... )
7.  abstract def isShutdown(): Boolean
   Definition Classes
     ExecutorService
8.  abstract def isTerminated(): Boolean
   Definition Classes
     ExecutorService
9.  abstract def reportFailure(cause: Throwable): Unit

   Reports that an asynchronous computation failed.

   Reports that an asynchronous computation failed.

   cause

     the cause of the failure

   Definition Classes
     ExecutionContext
10.  abstract def shutdown(): Unit
    Definition Classes
      ExecutorService
11.  abstract def shutdownNow(): java.util.List[Runnable]
    Definition Classes
      ExecutorService
12.  abstract def submit(arg0: Runnable): java.util.concurrent.Future[_]
    Definition Classes
      ExecutorService
13.  abstract def submit[T](arg0: Runnable, arg1: T): java.util.concurrent.Future[T]
    Definition Classes
      ExecutorService
14.  abstract def submit[T](arg0: Callable[T]): java.util.concurrent.Future[T]
    Definition Classes
      ExecutorService

### 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 ExecutionContextExecutorService to any2stringadd[ExecutionContextExecutorService] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (ExecutionContextExecutorService, B)
   Implicit
     This member is added by an implicit conversion from ExecutionContextExecutorService to ArrowAssoc[ExecutionContextExecutorService] 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.  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 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[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )
   Note

     not specified by SLS as a member of AnyRef

8.  def ensuring(cond: (ExecutionContextExecutorService) ⇒ Boolean, msg: ⇒ Any): ExecutionContextExecutorService
   Implicit
     This member is added by an implicit conversion from ExecutionContextExecutorService to Ensuring[ExecutionContextExecutorService] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
9.  def ensuring(cond: (ExecutionContextExecutorService) ⇒ Boolean): ExecutionContextExecutorService
   Implicit
     This member is added by an implicit conversion from ExecutionContextExecutorService to Ensuring[ExecutionContextExecutorService] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
10.  def ensuring(cond: Boolean, msg: ⇒ Any): ExecutionContextExecutorService
    Implicit
      This member is added by an implicit conversion from ExecutionContextExecutorService to Ensuring[ExecutionContextExecutorService] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
11.  def ensuring(cond: Boolean): ExecutionContextExecutorService
    Implicit
      This member is added by an implicit conversion from ExecutionContextExecutorService to Ensuring[ExecutionContextExecutorService] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
12.  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
13.  def equals(arg0: Any): 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
14.  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[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )
    Note

      not specified by SLS as a member of AnyRef

15.  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 ExecutionContextExecutorService to StringFormat[ExecutionContextExecutorService] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()
16.  final def getClass(): Class[_]

    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
17.  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
18.  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
19.  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
20.  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
    Note

      not specified by SLS as a member of AnyRef

21.  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
    Note

      not specified by SLS as a member of AnyRef

22.  final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
      AnyRef
23.  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
24.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
25.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
26.  final def wait(arg0: Long): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
27.  def →[B](y: B): (ExecutionContextExecutorService, B)
    Implicit
      This member is added by an implicit conversion from ExecutionContextExecutorService to ArrowAssoc[ExecutionContextExecutorService] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Deprecated Value Members

1.  def prepare(): ExecutionContext

   Prepares for the execution of a task.

   Prepares for the execution of a task. Returns the prepared execution context. The recommended implementation of `prepare` is to return `this`.

   This method should no longer be overridden or called. It was originally expected that `prepare` would be called by all libraries that consume ExecutionContexts, in order to capture thread local context. However, this usage has proven difficult to implement in practice and instead it is now better to avoid using `prepare` entirely.

   Instead, if an `ExecutionContext` needs to capture thread local context, it should capture that context when it is constructed, so that it doesn't need any additional preparation later.

   Definition Classes
     ExecutionContext
   Annotations
     @deprecated
   Deprecated

     (Since version 2.12.0) preparation of ExecutionContexts will be removed

### Inherited from ExecutorService

### Inherited from ExecutionContextExecutor

### Inherited from Executor

### Inherited from ExecutionContext

### Inherited from AnyRef

### Inherited from Any

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

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

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

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

### Ungrouped