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Android APIs
public class

Executors

extends Object
java.lang.Object
   ↳ java.util.concurrent.Executors

Class Overview

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
static Callable<Object> callable(Runnable task)
Returns a Callable object that, when called, runs the given task and returns null.
static Callable<Object> callable(PrivilegedExceptionAction<?> action)
Returns a Callable object that, when called, runs the given privileged exception action and returns its result.
static Callable<Object> callable(PrivilegedAction<?> action)
Returns a Callable object that, when called, runs the given privileged action and returns its result.
static <T> Callable<T> callable(Runnable task, T result)
Returns a Callable object that, when called, runs the given task and returns the given result.
static ThreadFactory defaultThreadFactory()
Returns a default thread factory used to create new threads.
static ExecutorService newCachedThreadPool()
Creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available.
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.
static ExecutorService newFixedThreadPool(int nThreads)
Creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue.
static ExecutorService newFixedThreadPool(int nThreads, 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.
static ScheduledExecutorService newScheduledThreadPool(int corePoolSize)
Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.
static ScheduledExecutorService newScheduledThreadPool(int corePoolSize, ThreadFactory threadFactory)
Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.
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.
static ExecutorService newSingleThreadExecutor()
Creates an Executor that uses a single worker thread operating off an unbounded queue.
static ScheduledExecutorService newSingleThreadScheduledExecutor()
Creates a single-threaded executor that can schedule commands to run after a given delay, or to execute periodically.
static ScheduledExecutorService newSingleThreadScheduledExecutor(ThreadFactory threadFactory)
Creates a single-threaded executor that can schedule commands to run after a given delay, or to execute periodically.
static <T> Callable<T> privilegedCallable(Callable<T> callable)
Legacy security code; do not use.
static <T> Callable<T> privilegedCallableUsingCurrentClassLoader(Callable<T> callable)
Returns a Callable object that will, when called, execute the given callable under the current with the current context class loader as the context class loader.
static ThreadFactory privilegedThreadFactory()
Legacy security code; do not use.
static ExecutorService unconfigurableExecutorService(ExecutorService executor)
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.
static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor)
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.
[Expand]
Inherited Methods
From class java.lang.Object

Public Methods

public static Callable<Object> callable (Runnable task)

Added in API level 1

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

Parameters
task the task to run
Returns
  • a callable object
Throws
NullPointerException if task null

public static Callable<Object> callable (PrivilegedExceptionAction<?> action)

Added in API level 9

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

Parameters
action the privileged exception action to run
Returns
  • a callable object
Throws
NullPointerException if action null

public static Callable<Object> callable (PrivilegedAction<?> action)

Added in API level 9

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

Parameters
action the privileged action to run
Returns
  • a callable object
Throws
NullPointerException if action null

public static Callable<T> callable (Runnable task, T result)

Added in API level 1

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 the task to run
result the result to return
Returns
  • a callable object
Throws
NullPointerException if task null

public static ThreadFactory defaultThreadFactory ()

Added in API level 1

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 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.

Returns
  • a thread factory

public static ExecutorService newCachedThreadPool ()

Added in API level 1

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.

Returns
  • the newly created thread pool

public static ExecutorService newCachedThreadPool (ThreadFactory threadFactory)

Added in API level 1

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 the factory to use when creating new threads
Returns
  • the newly created thread pool
Throws
NullPointerException if threadFactory is null

public static ExecutorService newFixedThreadPool (int nThreads)

Added in API level 1

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 the number of threads in the pool
Returns
  • the newly created thread pool
Throws
IllegalArgumentException if nThreads <= 0

public static ExecutorService newFixedThreadPool (int nThreads, ThreadFactory threadFactory)

Added in API level 1

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 the number of threads in the pool
threadFactory the factory to use when creating new threads
Returns
  • the newly created thread pool
Throws
NullPointerException if threadFactory is null
IllegalArgumentException if nThreads <= 0

public static ScheduledExecutorService newScheduledThreadPool (int corePoolSize)

Added in API level 1

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

Parameters
corePoolSize the number of threads to keep in the pool, even if they are idle.
Returns
  • a newly created scheduled thread pool
Throws
IllegalArgumentException if corePoolSize < 0

public static ScheduledExecutorService newScheduledThreadPool (int corePoolSize, ThreadFactory threadFactory)

Added in API level 1

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

Parameters
corePoolSize the number of threads to keep in the pool, even if they are idle.
threadFactory the factory to use when the executor creates a new thread.
Returns
  • a newly created scheduled thread pool
Throws
IllegalArgumentException if corePoolSize < 0
NullPointerException if threadFactory is null

public static ExecutorService newSingleThreadExecutor (ThreadFactory threadFactory)

Added in API level 1

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 the factory to use when creating new threads
Returns
  • the newly created single-threaded Executor
Throws
NullPointerException if threadFactory is null

public static ExecutorService newSingleThreadExecutor ()

Added in API level 1

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.

Returns
  • the newly created single-threaded Executor

public static ScheduledExecutorService newSingleThreadScheduledExecutor ()

Added in API level 1

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.

Returns
  • the newly created scheduled executor

public static ScheduledExecutorService newSingleThreadScheduledExecutor (ThreadFactory threadFactory)

Added in API level 1

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 the factory to use when creating new threads
Returns
  • a newly created scheduled executor
Throws
NullPointerException if threadFactory is null

public static Callable<T> privilegedCallable (Callable<T> callable)

Added in API level 1

Legacy security code; do not use.

public static Callable<T> privilegedCallableUsingCurrentClassLoader (Callable<T> callable)

Added in API level 1

Returns a Callable object that will, when called, execute the given callable under the current with the current context class loader as the context class loader.

Returns
  • a callable object
Throws
NullPointerException if callable null

public static ThreadFactory privilegedThreadFactory ()

Added in API level 1

Legacy security code; do not use.

public static ExecutorService unconfigurableExecutorService (ExecutorService executor)

Added in API level 1

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 the underlying implementation
Returns
  • an ExecutorService instance
Throws
NullPointerException if executor null

public static ScheduledExecutorService unconfigurableScheduledExecutorService (ScheduledExecutorService executor)

Added in API level 1

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 the underlying implementation
Returns
  • a ScheduledExecutorService instance
Throws
NullPointerException if executor null