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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
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 |
|---|
executor |
ScheduledExecutorService: the underlying implementation |
