306 lines
13 KiB
Java
306 lines
13 KiB
Java
/*
|
|
* Written by Doug Lea with assistance from members of JCP JSR-166
|
|
* Expert Group and released to the public domain, as explained at
|
|
* http://creativecommons.org/licenses/publicdomain
|
|
*/
|
|
|
|
package java.util.concurrent;
|
|
import java.util.List;
|
|
import java.util.Collection;
|
|
import java.security.PrivilegedAction;
|
|
import java.security.PrivilegedExceptionAction;
|
|
|
|
/**
|
|
* An {@link Executor} that provides methods to manage termination and
|
|
* methods that can produce a {@link Future} for tracking progress of
|
|
* one or more asynchronous tasks.
|
|
*
|
|
* <p>
|
|
* An <tt>ExecutorService</tt> can be shut down, which will cause it
|
|
* to stop accepting new tasks. After being shut down, the executor
|
|
* will eventually terminate, at which point no tasks are actively
|
|
* executing, no tasks are awaiting execution, and no new tasks can be
|
|
* submitted. An unused <tt>ExecutorService</tt> should be shut down
|
|
* to allow reclamation of its resources.
|
|
*
|
|
* <p> Method <tt>submit</tt> extends base method {@link
|
|
* Executor#execute} by creating and returning a {@link Future} that
|
|
* can be used to cancel execution and/or wait for completion.
|
|
* Methods <tt>invokeAny</tt> and <tt>invokeAll</tt> perform the most
|
|
* commonly useful forms of bulk execution, executing a collection of
|
|
* tasks and then waiting for at least one, or all, to
|
|
* complete. (Class {@link ExecutorCompletionService} can be used to
|
|
* write customized variants of these methods.)
|
|
*
|
|
* <p>The {@link Executors} class provides factory methods for the
|
|
* executor services provided in this package.
|
|
*
|
|
* <h3>Usage Example</h3>
|
|
*
|
|
* Here is a sketch of a network service in which threads in a thread
|
|
* pool service incoming requests. It uses the preconfigured {@link
|
|
* Executors#newFixedThreadPool} factory method:
|
|
*
|
|
* <pre>
|
|
* class NetworkService {
|
|
* private final ServerSocket serverSocket;
|
|
* private final ExecutorService pool;
|
|
*
|
|
* public NetworkService(int port, int poolSize)
|
|
* throws IOException {
|
|
* serverSocket = new ServerSocket(port);
|
|
* pool = Executors.newFixedThreadPool(poolSize);
|
|
* }
|
|
*
|
|
* public void serve() {
|
|
* try {
|
|
* for (;;) {
|
|
* pool.execute(new Handler(serverSocket.accept()));
|
|
* }
|
|
* } catch (IOException ex) {
|
|
* pool.shutdown();
|
|
* }
|
|
* }
|
|
* }
|
|
*
|
|
* class Handler implements Runnable {
|
|
* private final Socket socket;
|
|
* Handler(Socket socket) { this.socket = socket; }
|
|
* public void run() {
|
|
* // read and service request
|
|
* }
|
|
* }
|
|
* </pre>
|
|
*
|
|
* <p>Memory consistency effects: Actions in a thread prior to the
|
|
* submission of a {@code Runnable} or {@code Callable} task to an
|
|
* {@code ExecutorService}
|
|
* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
|
|
* any actions taken by that task, which in turn <i>happen-before</i> the
|
|
* result is retrieved via {@code Future.get()}.
|
|
*
|
|
* @since 1.5
|
|
* @author Doug Lea
|
|
*/
|
|
public interface ExecutorService extends Executor {
|
|
|
|
/**
|
|
* Initiates an orderly shutdown in which previously submitted
|
|
* tasks are executed, but no new tasks will be accepted.
|
|
* Invocation has no additional effect if already shut down.
|
|
*
|
|
* @throws SecurityException if a security manager exists and
|
|
* shutting down this ExecutorService may manipulate
|
|
* threads that the caller is not permitted to modify
|
|
* because it does not hold {@link
|
|
* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
|
|
* or the security manager's <tt>checkAccess</tt> method
|
|
* denies access.
|
|
*/
|
|
void shutdown();
|
|
|
|
/**
|
|
* Attempts to stop all actively executing tasks, halts the
|
|
* processing of waiting tasks, and returns a list of the tasks that were
|
|
* awaiting execution.
|
|
*
|
|
* <p>There are no guarantees beyond best-effort attempts to stop
|
|
* processing actively executing tasks. For example, typical
|
|
* implementations will cancel via {@link Thread#interrupt}, so any
|
|
* task that fails to respond to interrupts may never terminate.
|
|
*
|
|
* @return list of tasks that never commenced execution
|
|
* @throws SecurityException if a security manager exists and
|
|
* shutting down this ExecutorService may manipulate
|
|
* threads that the caller is not permitted to modify
|
|
* because it does not hold {@link
|
|
* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
|
|
* or the security manager's <tt>checkAccess</tt> method
|
|
* denies access.
|
|
*/
|
|
List<Runnable> shutdownNow();
|
|
|
|
/**
|
|
* Returns <tt>true</tt> if this executor has been shut down.
|
|
*
|
|
* @return <tt>true</tt> if this executor has been shut down
|
|
*/
|
|
boolean isShutdown();
|
|
|
|
/**
|
|
* Returns <tt>true</tt> if all tasks have completed following shut down.
|
|
* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
|
|
* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
|
|
*
|
|
* @return <tt>true</tt> if all tasks have completed following shut down
|
|
*/
|
|
boolean isTerminated();
|
|
|
|
/**
|
|
* Blocks until all tasks have completed execution after a shutdown
|
|
* request, or the timeout occurs, or the current thread is
|
|
* interrupted, whichever happens first.
|
|
*
|
|
* @param timeout the maximum time to wait
|
|
* @param unit the time unit of the timeout argument
|
|
* @return <tt>true</tt> if this executor terminated and
|
|
* <tt>false</tt> if the timeout elapsed before termination
|
|
* @throws InterruptedException if interrupted while waiting
|
|
*/
|
|
boolean awaitTermination(long timeout, TimeUnit unit)
|
|
throws InterruptedException;
|
|
|
|
|
|
/**
|
|
* Submits a value-returning task for execution and returns a
|
|
* Future representing the pending results of the task. The
|
|
* Future's <tt>get</tt> method will return the task's result upon
|
|
* successful completion.
|
|
*
|
|
* <p>
|
|
* If you would like to immediately block waiting
|
|
* for a task, you can use constructions of the form
|
|
* <tt>result = exec.submit(aCallable).get();</tt>
|
|
*
|
|
* <p> Note: The {@link Executors} class includes a set of methods
|
|
* that can convert some other common closure-like objects,
|
|
* for example, {@link java.security.PrivilegedAction} to
|
|
* {@link Callable} form so they can be submitted.
|
|
*
|
|
* @param task the task to submit
|
|
* @return a Future representing pending completion of the task
|
|
* @throws RejectedExecutionException if the task cannot be
|
|
* scheduled for execution
|
|
* @throws NullPointerException if the task is null
|
|
*/
|
|
<T> Future<T> submit(Callable<T> task);
|
|
|
|
/**
|
|
* Submits a Runnable task for execution and returns a Future
|
|
* representing that task. The Future's <tt>get</tt> method will
|
|
* return the given result upon successful completion.
|
|
*
|
|
* @param task the task to submit
|
|
* @param result the result to return
|
|
* @return a Future representing pending completion of the task
|
|
* @throws RejectedExecutionException if the task cannot be
|
|
* scheduled for execution
|
|
* @throws NullPointerException if the task is null
|
|
*/
|
|
<T> Future<T> submit(Runnable task, T result);
|
|
|
|
/**
|
|
* Submits a Runnable task for execution and returns a Future
|
|
* representing that task. The Future's <tt>get</tt> method will
|
|
* return <tt>null</tt> upon <em>successful</em> completion.
|
|
*
|
|
* @param task the task to submit
|
|
* @return a Future representing pending completion of the task
|
|
* @throws RejectedExecutionException if the task cannot be
|
|
* scheduled for execution
|
|
* @throws NullPointerException if the task is null
|
|
*/
|
|
Future<?> submit(Runnable task);
|
|
|
|
/**
|
|
* Executes the given tasks, returning a list of Futures holding
|
|
* their status and results when all complete.
|
|
* {@link Future#isDone} is <tt>true</tt> for each
|
|
* element of the returned list.
|
|
* Note that a <em>completed</em> 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.
|
|
*
|
|
* @param tasks the collection of tasks
|
|
* @return 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.
|
|
* @throws InterruptedException if interrupted while waiting, in
|
|
* which case unfinished tasks are cancelled.
|
|
* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
|
|
* @throws RejectedExecutionException if any task cannot be
|
|
* scheduled for execution
|
|
*/
|
|
|
|
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
|
|
throws InterruptedException;
|
|
|
|
/**
|
|
* Executes the given tasks, returning a list of Futures holding
|
|
* their status and results
|
|
* when all complete or the timeout expires, whichever happens first.
|
|
* {@link Future#isDone} is <tt>true</tt> for each
|
|
* element of the returned list.
|
|
* Upon return, tasks that have not completed are cancelled.
|
|
* Note that a <em>completed</em> 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.
|
|
*
|
|
* @param tasks the collection of tasks
|
|
* @param timeout the maximum time to wait
|
|
* @param unit the time unit of the timeout argument
|
|
* @return 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.
|
|
* @throws InterruptedException if interrupted while waiting, in
|
|
* which case unfinished tasks are cancelled
|
|
* @throws NullPointerException if tasks, any of its elements, or
|
|
* unit are <tt>null</tt>
|
|
* @throws RejectedExecutionException if any task cannot be scheduled
|
|
* for execution
|
|
*/
|
|
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
|
|
long timeout, TimeUnit unit)
|
|
throws InterruptedException;
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* @param tasks the collection of tasks
|
|
* @return the result returned by one of the tasks
|
|
* @throws InterruptedException if interrupted while waiting
|
|
* @throws NullPointerException if tasks or any of its elements
|
|
* are <tt>null</tt>
|
|
* @throws IllegalArgumentException if tasks is empty
|
|
* @throws ExecutionException if no task successfully completes
|
|
* @throws RejectedExecutionException if tasks cannot be scheduled
|
|
* for execution
|
|
*/
|
|
<T> T invokeAny(Collection<? extends Callable<T>> tasks)
|
|
throws InterruptedException, ExecutionException;
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* @param tasks the collection of tasks
|
|
* @param timeout the maximum time to wait
|
|
* @param unit the time unit of the timeout argument
|
|
* @return the result returned by one of the tasks.
|
|
* @throws InterruptedException if interrupted while waiting
|
|
* @throws NullPointerException if tasks, any of its elements, or
|
|
* unit are <tt>null</tt>
|
|
* @throws TimeoutException if the given timeout elapses before
|
|
* any task successfully completes
|
|
* @throws ExecutionException if no task successfully completes
|
|
* @throws RejectedExecutionException if tasks cannot be scheduled
|
|
* for execution
|
|
*/
|
|
<T> T invokeAny(Collection<? extends Callable<T>> tasks,
|
|
long timeout, TimeUnit unit)
|
|
throws InterruptedException, ExecutionException, TimeoutException;
|
|
}
|