AbstractExecutorService
public abstract class AbstractExecutorService
extends Object implements ExecutorService
Known indirect subclasses |
Provides default implementations of ExecutorService execution methods. This class implements the submit, invokeAny and invokeAll methods using a RunnableFuture returned by newTaskFor, which defaults to the FutureTask class provided in this package. For example, the implementation of submit(Runnable) creates an associated RunnableFuture that is executed and returned. Subclasses may override the newTaskFor methods to return RunnableFuture implementations other than FutureTask.
Extension example. Here is a sketch of a class that customizes ThreadPoolExecutor to use a CustomTask class instead of the default FutureTask:
public class CustomThreadPoolExecutor extends ThreadPoolExecutor { static class CustomTask<V> implements RunnableFuture<V> { ... } protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) { return new CustomTask<V>(c); } protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) { return new CustomTask<V>(r, v); } // ... add constructors, etc. }
Summary
Public methods |
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<T> List<Future<T>> | invokeAll(Collection<? extends Callable<T>> tasks) Executes the given tasks, returning a list of Futures holding their status and results when all complete. |
<T> List<Future<T>> | invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) Executes the given tasks, returning a list of Futures holding their status and results when all complete or the timeout expires, whichever happens first. |
<T> T | invokeAny(Collection<? extends Callable<T>> tasks) Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do. |
<T> T | invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do before the given timeout elapses. |
<T> Future<T> | submit(Callable<T> task) Submits a value-returning task for execution and returns a Future representing the pending results of the task. |
<T> Future<T> | submit(Runnable task, T result) Submits a Runnable task for execution and returns a Future representing that task. |
Future<?> | submit(Runnable task) Submits a Runnable task for execution and returns a Future representing that task. |
Inherited methods |
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From class java.lang.Object Object | clone() Creates and returns a copy of this object. | boolean | equals(Object obj) Indicates whether some other object is "equal to" this one. | void | finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | final Class<?> | getClass() Returns the runtime class of this Object. | int | hashCode() Returns a hash code value for the object. | final void | notify() Wakes up a single thread that is waiting on this object's monitor. | final void | notifyAll() Wakes up all threads that are waiting on this object's monitor. | String | toString() Returns a string representation of the object. | final void | wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. | final void | wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. | final void | wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted. | |
From interface java.util.concurrent.ExecutorService abstract boolean | awaitTermination(long timeout, TimeUnit unit) Blocks until all tasks have completed execution after a shutdown request, or the timeout occurs, or the current thread is interrupted, whichever happens first. | default void | close() Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted. | abstract <T> List<Future<T>> | invokeAll(Collection<? extends Callable<T>> tasks) Executes the given tasks, returning a list of Futures holding their status and results when all complete. | abstract <T> List<Future<T>> | invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) Executes the given tasks, returning a list of Futures holding their status and results when all complete or the timeout expires, whichever happens first. | abstract <T> T | invokeAny(Collection<? extends Callable<T>> tasks) Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do. | abstract <T> T | invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do before the given timeout elapses. | abstract boolean | isShutdown() Returns true if this executor has been shut down. | abstract boolean | isTerminated() Returns true if all tasks have completed following shut down. | abstract void | shutdown() Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted. | abstract List<Runnable> | shutdownNow() Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution. | abstract Future<?> | submit(Runnable task) Submits a Runnable task for execution and returns a Future representing that task. | abstract <T> Future<T> | submit(Callable<T> task) Submits a value-returning task for execution and returns a Future representing the pending results of the task. | abstract <T> Future<T> | submit(Runnable task, T result) Submits a Runnable task for execution and returns a Future representing that task. | |
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Public constructors
AbstractExecutorService
public AbstractExecutorService ()
Constructor for subclasses to call.
Public methods
invokeAll
public List<Future<T>> invokeAll (Collection<? extends Callable<T>> tasks)
Executes the given tasks, returning a list of Futures holding their status and results when all complete. Future.isDone is true for each element of the returned list. Note that a completed task could have terminated either normally or by throwing an exception. The results of this method are undefined if the given collection is modified while this operation is in progress.
| Parameters |
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tasks | Collection: the collection of tasks |
| Returns |
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List<Future<T>> | a list of Futures representing the tasks, in the same sequential order as produced by the iterator for the given task list, each of which has completed |
invokeAll
public List<Future<T>> invokeAll (Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
Executes the given tasks, returning a list of Futures holding their status and results when all complete or the timeout expires, whichever happens first. Future.isDone is true for each element of the returned list. Upon return, tasks that have not completed are cancelled. Note that a completed task could have terminated either normally or by throwing an exception. The results of this method are undefined if the given collection is modified while this operation is in progress.
| Parameters |
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tasks | Collection: the collection of tasks |
timeout | long: the maximum time to wait |
unit | TimeUnit: the time unit of the timeout argument |
| Returns |
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List<Future<T>> | a list of Futures representing the tasks, in the same sequential order as produced by the iterator for the given task list. If the operation did not time out, each task will have completed. If it did time out, some of these tasks will not have completed. |
invokeAny
public T invokeAny (Collection<? extends Callable<T>> tasks)
Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do. Upon normal or exceptional return, tasks that have not completed are cancelled. The results of this method are undefined if the given collection is modified while this operation is in progress.
| Parameters |
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tasks | Collection: the collection of tasks |
| Returns |
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T | the result returned by one of the tasks |
invokeAny
public T invokeAny (Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do before the given timeout elapses. Upon normal or exceptional return, tasks that have not completed are cancelled. The results of this method are undefined if the given collection is modified while this operation is in progress.
| Parameters |
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tasks | Collection: the collection of tasks |
timeout | long: the maximum time to wait |
unit | TimeUnit: the time unit of the timeout argument |
| Returns |
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T | the result returned by one of the tasks |
submit
public Future<T> submit (Callable<T> task)
Submits a value-returning task for execution and returns a Future representing the pending results of the task. The Future's get method will return the task's result upon successful completion.
If you would like to immediately block waiting for a task, you can use constructions of the form result = exec.submit(aCallable).get();
Note: The Executors class includes a set of methods that can convert some other common closure-like objects, for example, PrivilegedAction to Callable form so they can be submitted.
| Parameters |
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task | Callable: the task to submit |
| Returns |
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Future<T> | a Future representing pending completion of the task |
submit
public Future<T> submit (Runnable task, T result)
Submits a Runnable task for execution and returns a Future representing that task. The Future's get method will return the given result upon successful completion.
| Parameters |
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task | Runnable: the task to submit |
result | T: the result to return |
| Returns |
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Future<T> | a Future representing pending completion of the task |
submit
public Future<?> submit (Runnable task)
Submits a Runnable task for execution and returns a Future representing that task. The Future's get method will return null upon successful completion.
| Parameters |
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task | Runnable: the task to submit |
| Returns |
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Future<?> | a Future representing pending completion of the task |
Protected methods
newTaskFor
protected RunnableFuture<T> newTaskFor (Runnable runnable, T value)
Returns a RunnableFuture for the given runnable and default value.
| Parameters |
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runnable | Runnable: the runnable task being wrapped |
value | T: the default value for the returned future |
| Returns |
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RunnableFuture<T> | a RunnableFuture which, when run, will run the underlying runnable and which, as a Future, will yield the given value as its result and provide for cancellation of the underlying task |
newTaskFor
protected RunnableFuture<T> newTaskFor (Callable<T> callable)
Returns a RunnableFuture for the given callable task.
| Parameters |
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callable | Callable: the callable task being wrapped |
| Returns |
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RunnableFuture<T> | a RunnableFuture which, when run, will call the underlying callable and which, as a Future, will yield the callable's result as its result and provide for cancellation of the underlying task |
