Added in API level 1

FutureTask

open class FutureTask<V : Any!> : RunnableFuture<V>
kotlin.Any
   ↳ java.util.concurrent.FutureTask

A cancellable asynchronous computation. This class provides a base implementation of Future, with methods to start and cancel a computation, query to see if the computation is complete, and retrieve the result of the computation. The result can only be retrieved when the computation has completed; the get methods will block if the computation has not yet completed. Once the computation has completed, the computation cannot be restarted or cancelled (unless the computation is invoked using runAndReset).

A FutureTask can be used to wrap a Callable or Runnable object. Because FutureTask implements Runnable, a FutureTask can be submitted to an Executor for execution.

In addition to serving as a standalone class, this class provides protected functionality that may be useful when creating customized task classes.

Summary

Public constructors
FutureTask(callable: Callable<V>!)

Creates a FutureTask that will, upon running, execute the given Callable.

FutureTask(runnable: Runnable!, result: V)

Creates a FutureTask that will, upon running, execute the given Runnable, and arrange that get will return the given result on successful completion.

Public methods
open Boolean
cancel(mayInterruptIfRunning: Boolean)

open V
get()

open V
get(timeout: Long, unit: TimeUnit!)

open Boolean

open Boolean

open Unit
run()

open String

Returns a string representation of this FutureTask.

Protected methods
open Unit

Protected method invoked when this task transitions to state isDone (whether normally or via cancellation).

open Boolean

Executes the computation without setting its result, and then resets this future to initial state, failing to do so if the computation encounters an exception or is cancelled.

open Unit
set(v: V)

Sets the result of this future to the given value unless this future has already been set or has been cancelled.

open Unit

Causes this future to report an ExecutionException with the given throwable as its cause, unless this future has already been set or has been cancelled.

Public constructors

FutureTask

Added in API level 1
FutureTask(callable: Callable<V>!)

Creates a FutureTask that will, upon running, execute the given Callable.

Parameters
callable Callable<V>!: the callable task
Exceptions
java.lang.NullPointerException if the callable is null

FutureTask

Added in API level 1
FutureTask(
    runnable: Runnable!,
    result: V)

Creates a FutureTask that will, upon running, execute the given Runnable, and arrange that get will return the given result on successful completion.

Parameters
runnable Runnable!: the runnable task
result V: the result to return on successful completion. If you don't need a particular result, consider using constructions of the form: Future<?> f = new FutureTask<Void>(runnable, null)
Exceptions
java.lang.NullPointerException if the runnable is null

Public methods

cancel

Added in API level 1
open fun cancel(mayInterruptIfRunning: Boolean): Boolean
Parameters
mayInterruptIfRunning Boolean: true if the thread executing this task should be interrupted (if the thread is known to the implementation); otherwise, in-progress tasks are allowed to complete
Return
Boolean false if the task could not be cancelled, typically because it has already completed; true otherwise. If two or more threads cause a task to be cancelled, then at least one of them returns true. Implementations may provide stronger guarantees.

get

Added in API level 1
open fun get(): V
Return
V the computed result
Exceptions
java.util.concurrent.CancellationException if the computation was cancelled
java.util.concurrent.ExecutionException if the computation threw an exception
java.lang.InterruptedException if the current thread was interrupted while waiting

get

Added in API level 1
open fun get(
    timeout: Long,
    unit: TimeUnit!
): V
Parameters
timeout Long: the maximum time to wait
unit TimeUnit!: the time unit of the timeout argument
Return
V the computed result
Exceptions
java.util.concurrent.CancellationException if the computation was cancelled
java.util.concurrent.ExecutionException if the computation threw an exception
java.lang.InterruptedException if the current thread was interrupted while waiting
java.util.concurrent.TimeoutException if the wait timed out

isCancelled

Added in API level 1
open fun isCancelled(): Boolean
Return
Boolean true if this task was cancelled before it completed

isDone

Added in API level 1
open fun isDone(): Boolean
Return
Boolean true if this task completed

run

Added in API level 1
open fun run(): Unit

toString

Added in API level 1
open fun toString(): String

Returns a string representation of this FutureTask.

Return
String a string representation of this FutureTask

Protected methods

done

Added in API level 1
protected open fun done(): Unit

Protected method invoked when this task transitions to state isDone (whether normally or via cancellation). The default implementation does nothing. Subclasses may override this method to invoke completion callbacks or perform bookkeeping. Note that you can query status inside the implementation of this method to determine whether this task has been cancelled.

runAndReset

Added in API level 1
protected open fun runAndReset(): Boolean

Executes the computation without setting its result, and then resets this future to initial state, failing to do so if the computation encounters an exception or is cancelled. This is designed for use with tasks that intrinsically execute more than once.

Return
Boolean true if successfully run and reset

set

Added in API level 1
protected open fun set(v: V): Unit

Sets the result of this future to the given value unless this future has already been set or has been cancelled.

This method is invoked internally by the #run method upon successful completion of the computation.

Parameters
v V: the value

setException

Added in API level 1
protected open fun setException(t: Throwable!): Unit

Causes this future to report an ExecutionException with the given throwable as its cause, unless this future has already been set or has been cancelled.

This method is invoked internally by the #run method upon failure of the computation.

Parameters
t Throwable!: the cause of failure