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java.util.concurrent
Class Executors
java.lang.Object
java.util.concurrent.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
.
-
Since:
-
1.5
Method Summary
|
static
Callable
<
Object
|
callable
(
PrivilegedAction
Returns a
Callable
|
static
Callable
<
Object
|
callable
(
PrivilegedExceptionAction
Returns a
Callable
|
static
Callable
<
Object
> |
callable
(
Runnable
task)
Returns a
Callable
object that, when called, runs the given task and returns
null
. |
static
|
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
set
of threads operating off a shared unbounded queue. |
static
ExecutorService
|
newFixedThreadPool
(int nThreads,
ThreadFactory
Creates a thread pool that reuses a fixed
number
set
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
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
|
privilegedCallable
(
Callable
<T> callable)
Returns a
Callable
object that will, when called, execute the given
callable
under the current access control context. |
static
|
privilegedCallableUsingCurrentClassLoader
(
Callable
<T> callable)
Returns a
Callable
object that will, when called, execute the given
callable
under the current access control context, with the current context class loader as the context class loader. |
static
ThreadFactory
|
privilegedThreadFactory
()
Returns a thread factory used to create new threads that have the same permissions as the current thread. |
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. |
Methods inherited from class java.lang.
Object
|
clone
,
equals
,
finalize
,
getClass
,
hashCode
,
notify
,
notifyAll
,
toString
,
wait
,
wait
,
wait
|
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.
Creates a thread pool that reuses a fixed set of threads operating off a shared unbounded queue.
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.
-
-
Parameters:
-
nThreads - the number of threads in the pool
-
Returns:
-
the newly created thread pool
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.
Creates a thread pool that reuses a fixed set of threads operating off a shared unbounded queue, using the provided ThreadFactory to create new threads when needed.
-
-
Parameters:
-
nThreads - the number of threads in the pool
-
threadFactory - the factory to use when creating new threads
-
Returns:
-
the newly created thread pool
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.
-
-
Returns:
-
the newly created single-threaded Executor
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 - the factory to use when creating new threads
-
Returns:
-
the newly created single-threaded Executor
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.
-
-
Returns:
-
the newly created thread pool
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 - the factory to use when creating new threads
-
Returns:
-
the newly created thread pool
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.
-
-
Returns:
-
the newly created scheduled executor
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 - the factory to use when creating new threads
-
Returns:
-
a newly created scheduled executor
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 - the number of threads to keep in the pool, even if they are idle.
-
Returns:
-
a newly created scheduled thread pool
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 - 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
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 - the underlying implementation
-
Returns:
-
an
ExecutorService
instance
-
Throws:
-
NullPointerException
- if executor null
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 - the underlying implementation
-
Returns:
-
a
ScheduledExecutorService
instance
-
Throws:
-
NullPointerException
- if executor null
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
. If there is a
SecurityManager
, it uses the group of
System.getSecurityManager()
, else the group of the thread invoking this
defaultThreadFactory
method. 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.
-
-
Returns:
-
a thread factory
privilegedThreadFactory
public static ThreadFactory privilegedThreadFactory()
-
Returns a thread factory used to create new threads that have the same permissions as the current thread. This factory creates threads with the same settings as
defaultThreadFactory()
, additionally setting the AccessControlContext and contextClassLoader of new threads to be the same as the thread invoking this
privilegedThreadFactory
method. A new
privilegedThreadFactory
can be created within an
AccessController.doPrivileged(java.security.PrivilegedAction
)
action setting the current thread's access control context to create threads with the selected permission settings holding within that action.
Note that while tasks running within such threads will have the same access control and class loader settings as the current thread, they need not have the same
ThreadLocal
or
InheritableThreadLocal
values. If necessary, particular values of thread locals can be set or reset before any task runs in
ThreadPoolExecutor
subclasses using
ThreadPoolExecutor.beforeExecute(java.lang.Thread, java.lang.Runnable)
. Also, if it is necessary to initialize worker threads to have the same InheritableThreadLocal settings as some other designated thread, you can create a custom ThreadFactory in which that thread waits for and services requests to create others that will inherit its values.
-
-
Returns:
-
a thread factory
-
Throws:
-
AccessControlException
- if the current access control context does not have permission to both get and set context class loader.
callable
public 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. 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
callable
public static Callable<Object> callable(Runnable task)
-
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
callable
public static Callable<Object> callable(PrivilegedAction<?> action) action)
-
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
callable
public static Callable<Object> callable(PrivilegedExceptionAction<?> action) action)
-
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
privilegedCallable
public static <T> Callable<T> privilegedCallable(Callable<T> callable)
-
Returns a
Callable
object that will, when called, execute the given
callable
under the current access control context. This method should normally be invoked within an
AccessController.doPrivileged(java.security.PrivilegedAction
)
action to create callables that will, if possible, execute under the selected permission settings holding within that action; or if not possible, throw an associated
AccessControlException
.
-
-
Parameters:
-
callable - the underlying task
-
Returns:
-
a callable object
-
Throws:
-
NullPointerException
- if callable null
privilegedCallableUsingCurrentClassLoader
public static <T> Callable<T> privilegedCallableUsingCurrentClassLoader(Callable<T> callable)
-
Returns a
Callable
object that will, when called, execute the given
callable
under the current access control context, with the current context class loader as the context class loader. This method should normally be invoked within an
AccessController.doPrivileged(java.security.PrivilegedAction
)
action to create callables that will, if possible, execute under the selected permission settings holding within that action; or if not possible, throw an associated
AccessControlException
.
-
-
Parameters:
-
callable - the underlying task
-
Returns:
-
a callable object
-
Throws:
-
NullPointerException
- if callable null
-
AccessControlException
- if the current access control context does not have permission to both set and get context class loader.