Executors
public class Executors
extends Object
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 |
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static Callable<Object> | callable(Runnable task) Returns a Callable object that, when called, runs the given task and returns null. |
static Callable<Object> | callable(PrivilegedAction<?> action) Returns a Callable object that, when called, runs the given privileged action and returns its result. |
static Callable<Object> | callable(PrivilegedExceptionAction<?> action) Returns a Callable object that, when called, runs the given privileged exception 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, 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 ExecutorService | newFixedThreadPool(int nThreads) Creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue. |
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 ExecutorService | newWorkStealingPool(int parallelism) Creates a thread pool that maintains enough threads to support the given parallelism level, and may use multiple queues to reduce contention. |
static ExecutorService | newWorkStealingPool() Creates a work-stealing thread pool using the number of available processors as its target parallelism level. |
static <T> Callable<T> | privilegedCallable(Callable<T> callable) This method was deprecated in API level 34. 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. |
static <T> Callable<T> | privilegedCallableUsingCurrentClassLoader(Callable<T> callable) This method was deprecated in API level 34. 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. |
static ThreadFactory | privilegedThreadFactory() This method was deprecated in API level 34. 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. |
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. |
Inherited methods |
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From class java.lang.Object Object | clone() Creates and returns a copy of this object. | boolean | equals(Object obj) Indicates whether some other object is "equal to" this one. | void | finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | final Class<?> | getClass() Returns the runtime class of this Object. | int | hashCode() Returns a hash code value for the object. | final void | notify() Wakes up a single thread that is waiting on this object's monitor. | final void | notifyAll() Wakes up all threads that are waiting on this object's monitor. | String | toString() Returns a string representation of the object. | final void | wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. | final void | wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. | final void | wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted. | |
Public methods
callable
public static Callable<Object> callable (Runnable task)
Returns a Callable object that, when called, runs the given task and returns null.
| Parameters |
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task | Runnable: the task to run |
callable
public static Callable<Object> callable (PrivilegedAction<?> action)
Returns a Callable object that, when called, runs the given privileged action and returns its result.
| Parameters |
|---|
action | PrivilegedAction: the privileged action to run |
callable
public static Callable<Object> callable (PrivilegedExceptionAction<?> action)
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 |
callable
public static Callable<T> callable (Runnable task, T result)
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 |
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task | Runnable: the task to run |
result | T: the result to return |
defaultThreadFactory
public static ThreadFactory defaultThreadFactory ()
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.
newCachedThreadPool
public static ExecutorService newCachedThreadPool ()
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.
newCachedThreadPool
public 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.
| Parameters |
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threadFactory | ThreadFactory: the factory to use when creating new threads |
newFixedThreadPool
public 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. 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 |
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nThreads | int: the number of threads in the pool |
threadFactory | ThreadFactory: the factory to use when creating new threads |
newFixedThreadPool
public static ExecutorService newFixedThreadPool (int nThreads)
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 |
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nThreads | int: the number of threads in the pool |
newScheduledThreadPool
public static ScheduledExecutorService newScheduledThreadPool (int corePoolSize)
Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.
| Parameters |
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corePoolSize | int: the number of threads to keep in the pool, even if they are idle |
newScheduledThreadPool
public 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.
| Parameters |
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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 |
newSingleThreadExecutor
public 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. Unlike the otherwise equivalent newFixedThreadPool(1, threadFactory) the returned executor is guaranteed not to be reconfigurable to use additional threads.
| Parameters |
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threadFactory | ThreadFactory: the factory to use when creating new threads |
newSingleThreadExecutor
public static ExecutorService newSingleThreadExecutor ()
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.
newSingleThreadScheduledExecutor
public static ScheduledExecutorService newSingleThreadScheduledExecutor ()
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.
newSingleThreadScheduledExecutor
public static ScheduledExecutorService newSingleThreadScheduledExecutor (ThreadFactory threadFactory)
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 |
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threadFactory | ThreadFactory: the factory to use when creating new threads |
newWorkStealingPool
public static ExecutorService newWorkStealingPool (int parallelism)
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 |
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parallelism | int: the targeted parallelism level |
newWorkStealingPool
public static ExecutorService newWorkStealingPool ()
Creates a work-stealing thread pool using the number of available processors as its target parallelism level.
privilegedCallable
public static Callable<T> privilegedCallable (Callable<T> callable)
This method was deprecated in API level 34.
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.
| Parameters |
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callable | Callable |
privilegedCallableUsingCurrentClassLoader
public static Callable<T> privilegedCallableUsingCurrentClassLoader (Callable<T> callable)
This method was deprecated in API level 34.
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.
| Parameters |
|---|
callable | Callable |
privilegedThreadFactory
public static ThreadFactory privilegedThreadFactory ()
This method was deprecated in API level 34.
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
public 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. This provides a way to safely "freeze" configuration and disallow tuning of a given concrete implementation.
| Parameters |
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executor | ExecutorService: the underlying implementation |
unconfigurableScheduledExecutorService
public 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. This provides a way to safely "freeze" configuration and disallow tuning of a given concrete implementation.
| Parameters |
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executor | ScheduledExecutorService: the underlying implementation |
