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java.lang.Object
edu.emory.mathcs.backport.java.util.concurrent.Executors
public class Executors
extends java.lang.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.
Method Summary | |
static Callable | |
static Callable | |
static Callable | |
static Callable | |
static ThreadFactory |
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static ExecutorService |
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static ExecutorService |
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static ExecutorService |
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static ExecutorService |
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static ScheduledExecutorService |
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static ScheduledExecutorService |
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static ExecutorService |
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static ExecutorService |
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static ScheduledExecutorService |
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static ScheduledExecutorService |
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static Callable |
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static Callable |
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static ThreadFactory |
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static ExecutorService |
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static ScheduledExecutorService |
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public static Callable callable(PrivilegedAction action)
Returns aCallable
object that, when called, runs the given privileged action and returns its result.
- Parameters:
action
- the privileged action to run
- Returns:
- a callable object
public static Callable callable(PrivilegedExceptionAction action)
Returns aCallable
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
public static Callable callable(Runnable task)
Returns aCallable
object that, when called, runs the given task and returns null.
- Parameters:
task
- the task to run
- Returns:
- a callable object
public static Callable callable(Runnable task, Object result)
Returns aCallable
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 runresult
- the result to return
- Returns:
- a callable object
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 sameThreadGroup
. If there is ajava.lang.SecurityManager
, it uses the group ofSystem.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 viaThread.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
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 usingThreadPoolExecutor
constructors.
- Returns:
- the newly created thread pool
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
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 explicitlyshutdown
.
- Parameters:
nThreads
- the number of threads in the pool
- Returns:
- the newly created thread pool
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 explicitlyshutdown
.
- Parameters:
nThreads
- the number of threads in the poolthreadFactory
- the factory to use when creating new threads
- Returns:
- the newly created thread pool
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
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
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
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
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
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
public static Callable privilegedCallable(Callable callable)
Returns aCallable
object that will, when called, execute the given callable under the current access control context. This method should normally be invoked within anAccessController.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 associatedAccessControlException
.
- Parameters:
callable
- the underlying task
- Returns:
- a callable object
public static Callable privilegedCallableUsingCurrentClassLoader(Callable callable)
Returns aCallable
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 anAccessController.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 associatedAccessControlException
.
- Parameters:
callable
- the underlying task
- Returns:
- a callable object
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 asdefaultThreadFactory()
, 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 anAccessController.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 samejava.lang.ThreadLocal
orjava.lang.InheritableThreadLocal
values. If necessary, particular values of thread locals can be set or reset before any task runs inThreadPoolExecutor
subclasses usingThreadPoolExecutor.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.
- Returns:
- a thread factory
public static ExecutorService unconfigurableExecutorService(ExecutorService executor)
Returns an object that delegates all definedExecutorService
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
public static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor)
Returns an object that delegates all definedScheduledExecutorService
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