Future

Creates a new promise.

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

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

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

The contained value of this Future. Before this Future is completed the value will be None. After completion the value will be Some(Right(t)) if it contains a valid result, or Some(Left(error)) if it contains an exception.

Test two objects for inequality.

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.

Test two objects for equality. The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

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 => sys.error("runtime exception")
 } andThen {
   case Failure(t) => println(t)
   case Success(v) => println(v)
 }

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.

Create a copy of the receiver object.

The default implementation of the clone method is platform dependent.

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 or times out, the resulting future also fails or times out, respectively.

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
 }
 await(0) g // evaluates to 5
 await(0) h // throw a NoSuchElementException

Creates a new future which holds the result of either this future or that future, depending on which future was completed first.

Note: using this method yields nondeterministic dataflow programs.

Example:

 val f = future { sys.error("failed") }
 val g = future { 5 }
 val h = f either g
 await(0) h // evaluates to either 5 or throws a runtime exception

Tests whether the argument (arg0) 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).

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

See also equals in Any.

Returns a failed projection of this future.

The failed projection is a future holding a value of type Throwable.

It is completed with a value which is the throwable of the original future in case the original future is failed.

It is failed with a NoSuchElementException if the original future is completed successfully.

Blocking on this future returns a value if the original future is completed with an exception and throws a corresponding exception if the original future fails.

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 { sys.error("failed") }
 val g = future { 5 }
 val h = f orElse g
 await(0) h // evaluates to 5

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 or times out, the resulting future also fails or times out, respectively.

Example:

 val f = future { 5 }
 val g = f filter { _ % 2 == 1 }
 val h = f filter { _ % 2 == 0 }
 await(0) g // evaluates to 5
 await(0) h // throw a NoSuchElementException

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.

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.

$forComprehensionExample

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

Will not be called if the future fails.

A representation that corresponds to the dynamic class of the receiver object.

The nature of the representation is platform dependent.

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

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.

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.

$forComprehensionExample

Equivalent to !(this eq that).

Wakes up a single thread that is waiting on the receiver object's monitor.

Wakes up all threads that are waiting on the receiver object's monitor.

When this future is completed with a failure (i.e. with a throwable), apply the provided callback to the throwable.

The 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 - 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 a ExecutionException with one of the exceptions above as the cause. If a future is failed with a scala.runtime.NonLocalReturnControl, it is completed with a value instead from that throwable instead instead.

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

Will not be called in case that the future is completed with a value.

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

When this future is completed successfully (i.e. with a value), apply the provided partial function to the value if the partial function is defined at that value.

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

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

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 ￢ﾇﾒ 0 } // result: 0
 future (6 / 0) recover { case e: NotFoundException   ￢ﾇﾒ 0 } // result: exception
 future (6 / 2) recover { case e: ArithmeticException ￢ﾇﾒ 0 } // result: 3

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

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.

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

If this future fails, the resulting future is failed with the throwable stored in this. Otherwise, if that future fails, the resulting future is failed with the throwable stored in that.