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 | Description |
---|---|---|
static Callable |
callable |
Returns a Callable object that, when called, runs the given task and returns null . |
static <T> Callable |
callable |
Returns a Callable object that, when called, runs the given task and returns the given result. |
static Callable |
callable |
Returns a Callable object that, when called, runs the given privileged action and returns its result. |
static Callable |
callable |
Returns a Callable object that, when called, runs the given privileged exception action and returns its 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 |
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 |
Creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue. |
static ExecutorService |
newFixedThreadPool |
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 |
Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically. |
static ScheduledExecutorService |
newScheduledThreadPool |
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 |
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 |
Creates a single-threaded executor that can schedule commands to run after a given delay, or to execute periodically. |
static ExecutorService |
newThreadPerTaskExecutor |
Creates an Executor that starts a new Thread for each task. |
static ExecutorService |
newVirtualThreadPerTaskExecutor() |
Creates an Executor that starts a new virtual Thread for each task. |
static ExecutorService |
newWorkStealingPool() |
Creates a work-stealing thread pool using the number of available processors as its target parallelism level. |
static ExecutorService |
newWorkStealingPool |
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 |
privilegedCallable |
Deprecated, for removal: This API element is subject to removal in a future version. This method is only useful in conjunction with the Security Manager, which is deprecated and subject to removal in a future release. |
static <T> Callable |
privilegedCallableUsingCurrentClassLoader |
Deprecated, for removal: This API element is subject to removal in a future version. This method is only useful in conjunction with the Security Manager, which is deprecated and subject to removal in a future release. |
static ThreadFactory |
privilegedThreadFactory() |
Deprecated, for removal: This API element is subject to removal in a future version. This method is only useful in conjunction with the Security Manager, which is deprecated and subject to removal in a future release. |
static ExecutorService |
unconfigurableExecutorService |
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 |
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()
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 ExecutorService newThreadPerTaskExecutor(ThreadFactory threadFactory)
Invoking cancel(true)
on a Future
representing the pending result of a task submitted to the Executor will interrupt
the thread executing the task.
threadFactory
- the factory to use when creating new threadsNullPointerException
- if threadFactory is nullpublic static ExecutorService newVirtualThreadPerTaskExecutor()
This method is equivalent to invoking newThreadPerTaskExecutor(ThreadFactory)
with a thread factory that creates virtual threads.
public 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
. 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.@Deprecated(since="17", forRemoval=true) public static ThreadFactory privilegedThreadFactory()
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
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(Thread, 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.
AccessControlException
- if the current access control context does not have permission to both get and set context class loaderpublic 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 null@Deprecated(since="17", forRemoval=true) public static <T> Callable<T> privilegedCallable(Callable<T> callable)
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
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
.T
- the type of the callable's resultcallable
- the underlying taskNullPointerException
- if callable null@Deprecated(since="17", forRemoval=true) public static <T> Callable<T> privilegedCallableUsingCurrentClassLoader(Callable<T> callable)
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
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
.T
- the type of the callable's resultcallable
- the underlying taskNullPointerException
- if callable nullAccessControlException
- if the current access control context does not have permission to both set and get context class loader
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