* #### newFixedThreadPool
public static [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") 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](../../../java/util/concurrent/ExecutorService.html#shutdown%28%29).
Parameters:
`nThreads` \- the number of threads in the pool
Returns:
the newly created thread pool
Throws:
`[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if `nThreads <= 0`
* #### newWorkStealingPool
public static [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") 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` \- the targeted parallelism level
Returns:
the newly created thread pool
Throws:
`[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if `parallelism <= 0`
Since:
1.8
* #### newWorkStealingPool
public static [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") newWorkStealingPool()
Creates a work-stealing thread pool using the number of[available processors](../../../java/lang/Runtime.html#availableProcessors%28%29) as its target parallelism level.
Returns:
the newly created thread pool
Since:
1.8
See Also:
[newWorkStealingPool(int)](../../../java/util/concurrent/Executors.html#newWorkStealingPool%28int%29)
* #### newFixedThreadPool
public static [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") newFixedThreadPool(int nThreads,
[ThreadFactory](../../../java/util/concurrent/ThreadFactory.html "interface in java.util.concurrent") 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](../../../java/util/concurrent/ExecutorService.html#shutdown%28%29).
Parameters:
`nThreads` \- the number of threads in the pool
`threadFactory` \- the factory to use when creating new threads
Returns:
the newly created thread pool
Throws:
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if threadFactory is null
`[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if `nThreads <= 0`
* #### newSingleThreadExecutor
public static [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") 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](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") newSingleThreadExecutor([ThreadFactory](../../../java/util/concurrent/ThreadFactory.html "interface in java.util.concurrent") 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
Throws:
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if threadFactory is null
* #### newCachedThreadPool
public static [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") 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](../../../java/util/concurrent/ThreadPoolExecutor.html "class in java.util.concurrent") constructors.
Returns:
the newly created thread pool
* #### newCachedThreadPool
public static [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") newCachedThreadPool([ThreadFactory](../../../java/util/concurrent/ThreadFactory.html "interface in java.util.concurrent") 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
Throws:
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if threadFactory is null
* #### newSingleThreadScheduledExecutor
public static [ScheduledExecutorService](../../../java/util/concurrent/ScheduledExecutorService.html "interface in java.util.concurrent") 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](../../../java/util/concurrent/ScheduledExecutorService.html "interface in java.util.concurrent") newSingleThreadScheduledExecutor([ThreadFactory](../../../java/util/concurrent/ThreadFactory.html "interface in java.util.concurrent") 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
Throws:
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if threadFactory is null
* #### newScheduledThreadPool
public static [ScheduledExecutorService](../../../java/util/concurrent/ScheduledExecutorService.html "interface in java.util.concurrent") 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
Throws:
`[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if `corePoolSize < 0`
* #### newScheduledThreadPool
public static [ScheduledExecutorService](../../../java/util/concurrent/ScheduledExecutorService.html "interface in java.util.concurrent") newScheduledThreadPool(int corePoolSize,
[ThreadFactory](../../../java/util/concurrent/ThreadFactory.html "interface in java.util.concurrent") 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
Throws:
`[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if `corePoolSize < 0`
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if threadFactory is null
* #### unconfigurableExecutorService
public static [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") unconfigurableExecutorService([ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") executor)
Returns an object that delegates all defined [ExecutorService](../../../java/util/concurrent/ExecutorService.html "interface in java.util.concurrent") 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](../../../java/lang/NullPointerException.html "class in java.lang")` \- if executor null
* #### unconfigurableScheduledExecutorService
public static [ScheduledExecutorService](../../../java/util/concurrent/ScheduledExecutorService.html "interface in java.util.concurrent") unconfigurableScheduledExecutorService([ScheduledExecutorService](../../../java/util/concurrent/ScheduledExecutorService.html "interface in java.util.concurrent") executor)
Returns an object that delegates all defined [ScheduledExecutorService](../../../java/util/concurrent/ScheduledExecutorService.html "interface in java.util.concurrent") 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](../../../java/lang/NullPointerException.html "class in java.lang")` \- if executor null
* #### defaultThreadFactory
public static [ThreadFactory](../../../java/util/concurrent/ThreadFactory.html "interface in java.util.concurrent") 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](../../../java/lang/ThreadGroup.html "class in java.lang"). If there is a [SecurityManager](../../../java/lang/SecurityManager.html "class in java.lang"), it uses the group of [System.getSecurityManager()](../../../java/lang/System.html#getSecurityManager%28%29), 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()](../../../java/lang/Thread.html#getName%28%29) 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](../../../java/util/concurrent/ThreadFactory.html "interface in java.util.concurrent") 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()](../../../java/util/concurrent/Executors.html#defaultThreadFactory%28%29), 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/AccessController.html#doPrivileged%28java.security.PrivilegedAction%29) 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](../../../java/lang/ThreadLocal.html "class in java.lang") or [InheritableThreadLocal](../../../java/lang/InheritableThreadLocal.html "class in java.lang") values. If necessary, particular values of thread locals can be set or reset before any task runs in [ThreadPoolExecutor](../../../java/util/concurrent/ThreadPoolExecutor.html "class in java.util.concurrent") subclasses using[ThreadPoolExecutor.beforeExecute(Thread, Runnable)](../../../java/util/concurrent/ThreadPoolExecutor.html#beforeExecute%28java.lang.Thread,java.lang.Runnable%29). 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](../../../java/security/AccessControlException.html "class in java.security")` \- if the current access control context does not have permission to both get and set context class loader
* #### callable
public static <T> [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent")<T> callable([Runnable](../../../java/lang/Runnable.html "interface in java.lang") task,
T result)
Returns a [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent") 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.
Type Parameters:
`T` \- the type of the result
Parameters:
`task` \- the task to run
`result` \- the result to return
Returns:
a callable object
Throws:
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if task null
* #### callable
public static [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent")<[Object](../../../java/lang/Object.html "class in java.lang")> callable([Runnable](../../../java/lang/Runnable.html "interface in java.lang") task)
Returns a [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent") object that, when called, runs the given task and returns `null`.
Parameters:
`task` \- the task to run
Returns:
a callable object
Throws:
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if task null
* #### callable
public static [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent")<[Object](../../../java/lang/Object.html "class in java.lang")> callable([PrivilegedAction](../../../java/security/PrivilegedAction.html "interface in java.security")<?> action)
Returns a [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent") 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](../../../java/lang/NullPointerException.html "class in java.lang")` \- if action null
* #### callable
public static [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent")<[Object](../../../java/lang/Object.html "class in java.lang")> callable([PrivilegedExceptionAction](../../../java/security/PrivilegedExceptionAction.html "interface in java.security")<?> action)
Returns a [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent") 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](../../../java/lang/NullPointerException.html "class in java.lang")` \- if action null
* #### privilegedCallable
public static <T> [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent")<T> privilegedCallable([Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent")<T> callable)
Returns a [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent") 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/AccessController.html#doPrivileged%28java.security.PrivilegedAction%29) 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](../../../java/security/AccessControlException.html "class in java.security").
Type Parameters:
`T` \- the type of the callable's result
Parameters:
`callable` \- the underlying task
Returns:
a callable object
Throws:
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if callable null
* #### privilegedCallableUsingCurrentClassLoader
public static <T> [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent")<T> privilegedCallableUsingCurrentClassLoader([Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent")<T> callable)
Returns a [Callable](../../../java/util/concurrent/Callable.html "interface in java.util.concurrent") 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/AccessController.html#doPrivileged%28java.security.PrivilegedAction%29) 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](../../../java/security/AccessControlException.html "class in java.security").
Type Parameters:
`T` \- the type of the callable's result
Parameters:
`callable` \- the underlying task
Returns:
a callable object
Throws:
`[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")` \- if callable null
`[AccessControlException](../../../java/security/AccessControlException.html "class in java.security")` \- if the current access control context does not have permission to both set and get context class loader