Added in API level 1

Executors

open class Executors

kotlin.Any
↳	java.util.concurrent.Executors

Factory and utility methods for Executor, ExecutorService, ScheduledExecutorService, ThreadFactory, and Callable classes defined in this package. This class supports the following kinds of methods:

• Methods that create and return an ExecutorService set up with commonly useful configuration settings.
• Methods that create and return a ScheduledExecutorService set up with commonly useful configuration settings.
• Methods that create and return a "wrapped" ExecutorService, that disables reconfiguration by making implementation-specific methods inaccessible.
• Methods that create and return a ThreadFactory that sets newly created threads to a known state.
• Methods that create and return a Callable out of other closure-like forms, so they can be used in execution methods requiring Callable.

Summary

Public methods
open static Callable<T>!	callable(task: Runnable!, result: T) Returns a Callable object that, when called, runs the given task and returns the given result.
open static Callable<Any!>!	callable(task: Runnable!) Returns a Callable object that, when called, runs the given task and returns null.
open static Callable<Any!>!	callable(action: PrivilegedAction<*>!) Returns a Callable object that, when called, runs the given privileged action and returns its result.
open static Callable<Any!>!	callable(action: PrivilegedExceptionAction<*>!) Returns a Callable object that, when called, runs the given privileged exception action and returns its result.
open static ThreadFactory!	defaultThreadFactory() Returns a default thread factory used to create new threads.
open static ExecutorService!	newCachedThreadPool() Creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available.
open static ExecutorService!	newCachedThreadPool(threadFactory: ThreadFactory!) Creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available, and uses the provided ThreadFactory to create new threads when needed.
open static ExecutorService!	newFixedThreadPool(nThreads: Int) Creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue.
open static ExecutorService!	newFixedThreadPool(nThreads: Int, threadFactory: ThreadFactory!) Creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue, using the provided ThreadFactory to create new threads when needed.
open static ScheduledExecutorService!	newScheduledThreadPool(corePoolSize: Int) Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.
open static ScheduledExecutorService!	newScheduledThreadPool(corePoolSize: Int, threadFactory: ThreadFactory!) Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.
open static ExecutorService!	newSingleThreadExecutor() Creates an Executor that uses a single worker thread operating off an unbounded queue.
open static ExecutorService!	newSingleThreadExecutor(threadFactory: ThreadFactory!) Creates an Executor that uses a single worker thread operating off an unbounded queue, and uses the provided ThreadFactory to create a new thread when needed.
open static ScheduledExecutorService!	newSingleThreadScheduledExecutor() Creates a single-threaded executor that can schedule commands to run after a given delay, or to execute periodically.
open static ScheduledExecutorService!	newSingleThreadScheduledExecutor(threadFactory: ThreadFactory!) Creates a single-threaded executor that can schedule commands to run after a given delay, or to execute periodically.
open static ExecutorService!	newWorkStealingPool(parallelism: Int) Creates a thread pool that maintains enough threads to support the given parallelism level, and may use multiple queues to reduce contention.
open static ExecutorService!	newWorkStealingPool() Creates a work-stealing thread pool using the number of available processors as its target parallelism level.
open static Callable<T>!	privilegedCallable(callable: Callable<T>!) Legacy security code; do not use.
open static Callable<T>!	privilegedCallableUsingCurrentClassLoader(callable: Callable<T>!) Legacy security code; do not use.
open static ThreadFactory!	privilegedThreadFactory() Legacy security code; do not use.
open static ExecutorService!	unconfigurableExecutorService(executor: ExecutorService!) Returns an object that delegates all defined ExecutorService methods to the given executor, but not any other methods that might otherwise be accessible using casts.
open static ScheduledExecutorService!	unconfigurableScheduledExecutorService(executor: ScheduledExecutorService!) Returns an object that delegates all defined ScheduledExecutorService methods to the given executor, but not any other methods that might otherwise be accessible using casts.

Public methods

callable

Added in API level 1

open static fun <T : Any!> callable(
    task: Runnable!, 
    result: T
): Callable<T>!

Returns a Callable object that, when called, runs the given task and returns the given result. This can be useful when applying methods requiring a Callable to an otherwise resultless action.

Parameters
task	Runnable!: the task to run
result	T: the result to return
<T>	the type of the result

Return
Callable<T>!	a callable object

Exceptions
java.lang.NullPointerException	if task null

callable

Added in API level 1

open static fun callable(task: Runnable!): Callable<Any!>!

Returns a Callable object that, when called, runs the given task and returns null.

Parameters
task	Runnable!: the task to run

Return
Callable<Any!>!	a callable object

Exceptions
java.lang.NullPointerException	if task null

callable

Added in API level 1

open static fun callable(action: PrivilegedAction<*>!): Callable<Any!>!

Returns a Callable object that, when called, runs the given privileged action and returns its result.

Parameters
action	PrivilegedAction<*>!: the privileged action to run

Return
Callable<Any!>!	a callable object

Exceptions
java.lang.NullPointerException	if action null

callable

Added in API level 1

open static fun callable(action: PrivilegedExceptionAction<*>!): Callable<Any!>!

Returns a Callable object that, when called, runs the given privileged exception action and returns its result.

Parameters
action	PrivilegedExceptionAction<*>!: the privileged exception action to run

Return
Callable<Any!>!	a callable object

Exceptions
java.lang.NullPointerException	if action null

defaultThreadFactory

Added in API level 1

open static fun defaultThreadFactory(): ThreadFactory!

Returns a default thread factory used to create new threads. This factory creates all new threads used by an Executor in the same ThreadGroup. Each new thread is created as a non-daemon thread with priority set to the smaller of Thread.NORM_PRIORITY and the maximum priority permitted in the thread group. New threads have names accessible via Thread#getName of pool-N-thread-M, where N is the sequence number of this factory, and M is the sequence number of the thread created by this factory.

Return
ThreadFactory!	a thread factory

newCachedThreadPool

Added in API level 1

open static fun newCachedThreadPool(): ExecutorService!

Creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available. These pools will typically improve the performance of programs that execute many short-lived asynchronous tasks. Calls to execute will reuse previously constructed threads if available. If no existing thread is available, a new thread will be created and added to the pool. Threads that have not been used for sixty seconds are terminated and removed from the cache. Thus, a pool that remains idle for long enough will not consume any resources. Note that pools with similar properties but different details (for example, timeout parameters) may be created using ThreadPoolExecutor constructors.

Return
ExecutorService!	the newly created thread pool

newCachedThreadPool

Added in API level 1

open static fun newCachedThreadPool(threadFactory: ThreadFactory!): ExecutorService!

Creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available, and uses the provided ThreadFactory to create new threads when needed.

Parameters
threadFactory	ThreadFactory!: the factory to use when creating new threads

Return
ExecutorService!	the newly created thread pool

Exceptions
java.lang.NullPointerException	if threadFactory is null

newFixedThreadPool

Added in API level 1

open static fun newFixedThreadPool(nThreads: Int): ExecutorService!

Creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue. At any point, at most nThreads threads will be active processing tasks. If additional tasks are submitted when all threads are active, they will wait in the queue until a thread is available. If any thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks. The threads in the pool will exist until it is explicitly shutdown.

Parameters
nThreads	Int: the number of threads in the pool

Return
ExecutorService!	the newly created thread pool

Exceptions
java.lang.IllegalArgumentException	if nThreads <= 0

newFixedThreadPool

Added in API level 1

open static fun newFixedThreadPool(
    nThreads: Int, 
    threadFactory: ThreadFactory!
): ExecutorService!

Creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue, using the provided ThreadFactory to create new threads when needed. At any point, at most nThreads threads will be active processing tasks. If additional tasks are submitted when all threads are active, they will wait in the queue until a thread is available. If any thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks. The threads in the pool will exist until it is explicitly shutdown.

Parameters
nThreads	Int: the number of threads in the pool
threadFactory	ThreadFactory!: the factory to use when creating new threads

Return
ExecutorService!	the newly created thread pool

Exceptions
java.lang.NullPointerException	if threadFactory is null
java.lang.IllegalArgumentException	if nThreads <= 0

newScheduledThreadPool

Added in API level 1

open static fun newScheduledThreadPool(corePoolSize: Int): ScheduledExecutorService!

Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.

Parameters
corePoolSize	Int: the number of threads to keep in the pool, even if they are idle

Return
ScheduledExecutorService!	the newly created scheduled thread pool

Exceptions
java.lang.IllegalArgumentException	if corePoolSize < 0

newScheduledThreadPool

Added in API level 1

open static fun newScheduledThreadPool(
    corePoolSize: Int, 
    threadFactory: ThreadFactory!
): ScheduledExecutorService!

Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.

Parameters
corePoolSize	Int: the number of threads to keep in the pool, even if they are idle
threadFactory	ThreadFactory!: the factory to use when the executor creates a new thread

Return
ScheduledExecutorService!	the newly created scheduled thread pool

Exceptions
java.lang.IllegalArgumentException	if corePoolSize < 0
java.lang.NullPointerException	if threadFactory is null

newSingleThreadExecutor

Added in API level 1

open static fun newSingleThreadExecutor(): ExecutorService!

Creates an Executor that uses a single worker thread operating off an unbounded queue. (Note however that if this single thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks.) Tasks are guaranteed to execute sequentially, and no more than one task will be active at any given time. Unlike the otherwise equivalent newFixedThreadPool(1) the returned executor is guaranteed not to be reconfigurable to use additional threads.

Return
ExecutorService!	the newly created single-threaded Executor

newSingleThreadExecutor

Added in API level 1

open static fun newSingleThreadExecutor(threadFactory: ThreadFactory!): ExecutorService!

Creates an Executor that uses a single worker thread operating off an unbounded queue, and uses the provided ThreadFactory to create a new thread when needed. Unlike the otherwise equivalent newFixedThreadPool(1, threadFactory) the returned executor is guaranteed not to be reconfigurable to use additional threads.

Parameters
threadFactory	ThreadFactory!: the factory to use when creating new threads

Return
ExecutorService!	the newly created single-threaded Executor

Exceptions
java.lang.NullPointerException	if threadFactory is null

newSingleThreadScheduledExecutor

Added in API level 1

open static fun newSingleThreadScheduledExecutor(): ScheduledExecutorService!

Creates a single-threaded executor that can schedule commands to run after a given delay, or to execute periodically. (Note however that if this single thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks.) Tasks are guaranteed to execute sequentially, and no more than one task will be active at any given time. Unlike the otherwise equivalent newScheduledThreadPool(1) the returned executor is guaranteed not to be reconfigurable to use additional threads.

Return
ScheduledExecutorService!	the newly created scheduled executor

newSingleThreadScheduledExecutor

Added in API level 1

open static fun newSingleThreadScheduledExecutor(threadFactory: ThreadFactory!): ScheduledExecutorService!

Creates a single-threaded executor that can schedule commands to run after a given delay, or to execute periodically. (Note however that if this single thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks.) Tasks are guaranteed to execute sequentially, and no more than one task will be active at any given time. Unlike the otherwise equivalent newScheduledThreadPool(1, threadFactory) the returned executor is guaranteed not to be reconfigurable to use additional threads.

Parameters
threadFactory	ThreadFactory!: the factory to use when creating new threads

Return
ScheduledExecutorService!	the newly created scheduled executor

Exceptions
java.lang.NullPointerException	if threadFactory is null

newWorkStealingPool

Added in API level 24

open static fun newWorkStealingPool(parallelism: Int): ExecutorService!

Creates a thread pool that maintains enough threads to support the given parallelism level, and may use multiple queues to reduce contention. The parallelism level corresponds to the maximum number of threads actively engaged in, or available to engage in, task processing. The actual number of threads may grow and shrink dynamically. A work-stealing pool makes no guarantees about the order in which submitted tasks are executed.

Parameters
parallelism	Int: the targeted parallelism level

Return
ExecutorService!	the newly created thread pool

Exceptions
java.lang.IllegalArgumentException	if parallelism <= 0

newWorkStealingPool

Added in API level 24

open static fun newWorkStealingPool(): ExecutorService!

Creates a work-stealing thread pool using the number of available processors as its target parallelism level.

Return
ExecutorService!	the newly created thread pool

See Also

• #newWorkStealingPool(int)

privilegedCallable

Added in API level 1
Deprecated in API level 34

open static fun <T : Any!> privilegedCallable(callable: Callable<T>!): Callable<T>!

Deprecated: This method is only useful in conjunction with the Security Manager, which is deprecated and subject to removal in a future release. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method.

Legacy security code; do not use.

privilegedCallableUsingCurrentClassLoader

Added in API level 1
Deprecated in API level 34

open static fun <T : Any!> privilegedCallableUsingCurrentClassLoader(callable: Callable<T>!): Callable<T>!

Deprecated: This method is only useful in conjunction with the Security Manager, which is deprecated and subject to removal in a future release. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method.

Legacy security code; do not use.

privilegedThreadFactory

Added in API level 1
Deprecated in API level 34

open static fun privilegedThreadFactory(): ThreadFactory!

Deprecated: This method is only useful in conjunction with the Security Manager, which is deprecated and subject to removal in a future release. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method.

Legacy security code; do not use.

unconfigurableExecutorService

Added in API level 1

open static fun unconfigurableExecutorService(executor: ExecutorService!): ExecutorService!

Returns an object that delegates all defined ExecutorService methods to the given executor, but not any other methods that might otherwise be accessible using casts. This provides a way to safely "freeze" configuration and disallow tuning of a given concrete implementation.

Parameters
executor	ExecutorService!: the underlying implementation

Return
ExecutorService!	an ExecutorService instance

Exceptions
java.lang.NullPointerException	if executor null

unconfigurableScheduledExecutorService

Added in API level 1

open static fun unconfigurableScheduledExecutorService(executor: ScheduledExecutorService!): ScheduledExecutorService!

Returns an object that delegates all defined ScheduledExecutorService methods to the given executor, but not any other methods that might otherwise be accessible using casts. This provides a way to safely "freeze" configuration and disallow tuning of a given concrete implementation.

Parameters
executor	ScheduledExecutorService!: the underlying implementation

Return
ScheduledExecutorService!	a ScheduledExecutorService instance

Exceptions
java.lang.NullPointerException	if executor null