Package Summary Overview Summary

### class:Executors [NONE]
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:newFixedThreadPool(int) [NONE]
### 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. 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`. Parameters: `nThreads` - the number of threads in the pool Returns: the newly created thread pool Throws: `IllegalArgumentException` - if `nThreads <= 0`

### method:newWorkStealingPool(int) [NONE]
### newWorkStealingPool public 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. 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` - if `parallelism <= 0` Since: 1.8

### method:newWorkStealingPool() [NONE]
### newWorkStealingPool public static ExecutorService newWorkStealingPool() Creates a work-stealing thread pool using the number of available processors as its target parallelism level. Returns: the newly created thread pool Since: 1.8 See Also: `newWorkStealingPool(int)`

### method:newFixedThreadPool(int,java.util.concurrent.ThreadFactory) [NONE]
### 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. The threads in the pool will exist until it is explicitly `shutdown`. 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` - if threadFactory is null `IllegalArgumentException` - if `nThreads <= 0`

### method:newSingleThreadExecutor() [NONE]
### 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

### method:newSingleThreadExecutor(java.util.concurrent.ThreadFactory) [NONE]
### 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 Throws: `NullPointerException` - if threadFactory is null

### method:newCachedThreadPool() [NONE]
### 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

### method:newCachedThreadPool(java.util.concurrent.ThreadFactory) [NONE]
### 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 Throws: `NullPointerException` - if threadFactory is null

### method:newThreadPerTaskExecutor(java.util.concurrent.ThreadFactory) [ADDED]
### newThreadPerTaskExecutor public static ExecutorService newThreadPerTaskExecutor (ThreadFactory threadFactory) `newThreadPerTaskExecutor` is a preview API of the Java platform. Programs can only use `newThreadPerTaskExecutor` when preview features are enabled. Preview features may be removed in a future release, or upgraded to permanent features of the Java platform. Creates an Executor that starts a new Thread for each task. The number of threads created by the Executor is unbounded. Invoking `cancel(true)` on a `Future` representing the pending result of a task submitted to the Executor will `interrupt` the thread executing the task. Parameters: `threadFactory` - the factory to use when creating new threads Returns: a new executor that creates a new Thread for each task Throws: `NullPointerException` - if threadFactory is null Since: 19

### method:newVirtualThreadPerTaskExecutor() [ADDED]
### newVirtualThreadPerTaskExecutor public static ExecutorService newVirtualThreadPerTaskExecutor() `newVirtualThreadPerTaskExecutor` is a preview API of the Java platform. Programs can only use `newVirtualThreadPerTaskExecutor` when preview features are enabled. Preview features may be removed in a future release, or upgraded to permanent features of the Java platform. Creates an Executor that starts a new virtual Thread for each task. The number of threads created by the Executor is unbounded. This method is equivalent to invoking `newThreadPerTaskExecutor(ThreadFactory)`PREVIEW with a thread factory that creates virtual threads. Returns: a new executor that creates a new virtual Thread for each task Throws: `UnsupportedOperationException` - if preview features are not enabled Since: 19

### method:newSingleThreadScheduledExecutor() [NONE]
### 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

### method:newSingleThreadScheduledExecutor(java.util.concurrent.ThreadFactory) [NONE]
### 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: the newly created scheduled executor Throws: `NullPointerException` - if threadFactory is null

### method:newScheduledThreadPool(int) [NONE]
### 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: the newly created scheduled thread pool Throws: `IllegalArgumentException` - if `corePoolSize < 0`

### method:newScheduledThreadPool(int,java.util.concurrent.ThreadFactory) [NONE]
### 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: the newly created scheduled thread pool Throws: `IllegalArgumentException` - if `corePoolSize < 0` `NullPointerException` - if threadFactory is null

### method:unconfigurableExecutorService(java.util.concurrent.ExecutorService) [NONE]
### 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

### method:unconfigurableScheduledExecutorService(java.util.concurrent.ScheduledExecutorService) [NONE]
### 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

### method:defaultThreadFactory() [NONE]
### 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

### method:privilegedThreadFactory() [NONE]
### privilegedThreadFactory @Deprecated(since="17", forRemoval=true) public 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. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method. 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` 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. 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. 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` - if task null

### method:callable(java.lang.Runnable) [NONE]
### 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

### method:callable(java.security.PrivilegedAction) [NONE]
### callable public static Callable<Object> callable (PrivilegedAction<?> 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

### method:callable(java.security.PrivilegedExceptionAction) [NONE]
### callable public static Callable<Object> callable (PrivilegedExceptionAction<?> 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

### method:privilegedCallable(java.util.concurrent.Callable) [NONE]
### privilegedCallable @Deprecated(since="17", forRemoval=true) public static <T> Callable<T> privilegedCallable (Callable<T> callable) 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. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method. 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` 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`. Type Parameters: `T` - the type of the callable's result Parameters: `callable` - the underlying task Returns: a callable object Throws: `NullPointerException` - if callable null

### method:privilegedCallableUsingCurrentClassLoader(java.util.concurrent.Callable) [NONE]
### privilegedCallableUsingCurrentClassLoader @Deprecated(since="17", forRemoval=true) public static <T> Callable<T> privilegedCallableUsingCurrentClassLoader (Callable<T> callable) 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. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method. 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` 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`. Type Parameters: `T` - the type of the callable's result 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