public class Executors extends Object
Executor
, ExecutorService
, ScheduledExecutorService
, ThreadFactory
, and Callable
classes defined in this
package. This class supports the following kinds of methods:
ExecutorService
set up with commonly useful configuration settings.
ScheduledExecutorService
set up with commonly useful configuration settings.
ThreadFactory
that sets newly created threads to a known state.
Callable
out of other closure-like forms, so they can be used
in execution methods requiring Callable
.
Modifier and Type | Method and Description |
---|---|
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 Callable<Object> |
callable(Runnable task)
Returns a
Callable object that, when
called, runs the given task and returns null . |
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()
Creates an Executor that uses a single worker thread operating
off an unbounded queue.
|
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 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()
Creates a work-stealing thread pool using the number of
available processors
as its target parallelism level.
|
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 <T> Callable<T> |
privilegedCallable(Callable<T> callable)
Legacy security code; do not use.
|
static <T> Callable<T> |
privilegedCallableUsingCurrentClassLoader(Callable<T> callable)
Legacy security code; do not use.
|
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. |
public static ExecutorService newFixedThreadPool(int nThreads)
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
.nThreads
- the number of threads in the poolIllegalArgumentException
- if nThreads <= 0
public static ExecutorService newWorkStealingPool(int parallelism)
parallelism
- the targeted parallelism levelIllegalArgumentException
- if parallelism <= 0
public static ExecutorService newWorkStealingPool()
newWorkStealingPool(int)
public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory)
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
.nThreads
- the number of threads in the poolthreadFactory
- the factory to use when creating new threadsNullPointerException
- if threadFactory is nullIllegalArgumentException
- if nThreads <= 0
public static ExecutorService newSingleThreadExecutor()
newFixedThreadPool(1)
the returned executor is
guaranteed not to be reconfigurable to use additional threads.public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory)
newFixedThreadPool(1, threadFactory)
the
returned executor is guaranteed not to be reconfigurable to use
additional threads.threadFactory
- the factory to use when creating new
threadsNullPointerException
- if threadFactory is nullpublic static ExecutorService newCachedThreadPool()
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.public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory)
threadFactory
- the factory to use when creating new threadsNullPointerException
- if threadFactory is nullpublic static ScheduledExecutorService newSingleThreadScheduledExecutor()
newScheduledThreadPool(1)
the returned executor is
guaranteed not to be reconfigurable to use additional threads.public static ScheduledExecutorService newSingleThreadScheduledExecutor(ThreadFactory threadFactory)
newScheduledThreadPool(1, threadFactory)
the returned executor is guaranteed not to be reconfigurable to
use additional threads.threadFactory
- the factory to use when creating new
threadsNullPointerException
- if threadFactory is nullpublic static ScheduledExecutorService newScheduledThreadPool(int corePoolSize)
corePoolSize
- the number of threads to keep in the pool,
even if they are idleIllegalArgumentException
- if corePoolSize < 0
public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize, ThreadFactory threadFactory)
corePoolSize
- the number of threads to keep in the pool,
even if they are idlethreadFactory
- the factory to use when the executor
creates a new threadIllegalArgumentException
- if corePoolSize < 0
NullPointerException
- if threadFactory is nullpublic static ExecutorService unconfigurableExecutorService(ExecutorService executor)
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.executor
- the underlying implementationExecutorService
instanceNullPointerException
- if executor nullpublic static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor)
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.executor
- the underlying implementationScheduledExecutorService
instanceNullPointerException
- if executor nullpublic static ThreadFactory defaultThreadFactory()
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.public static ThreadFactory privilegedThreadFactory()
public static <T> Callable<T> callable(Runnable task, T result)
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.T
- the type of the resulttask
- the task to runresult
- the result to returnNullPointerException
- if task nullpublic static Callable<Object> callable(Runnable task)
Callable
object that, when
called, runs the given task and returns null
.task
- the task to runNullPointerException
- if task nullpublic static Callable<Object> callable(PrivilegedAction<?> action)
Callable
object that, when
called, runs the given privileged action and returns its result.action
- the privileged action to runNullPointerException
- if action nullpublic static Callable<Object> callable(PrivilegedExceptionAction<?> action)
Callable
object that, when
called, runs the given privileged exception action and returns
its result.action
- the privileged exception action to runNullPointerException
- if action nullpublic static <T> Callable<T> privilegedCallable(Callable<T> callable)