/*
* @(#)ExecutorService.java 1.6 04/07/12
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
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.
*
* <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>
* @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 if any
* tasks mask or fail to respond to interrupts, they 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.
*
* <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 task cannot be scheduled
* for execution
* @throws NullPointerException if task null
*/
<T> Future<T> submit(Callable<T> task);
/**
* Submits a Runnable task for execution and returns a Future
* representing that task that will upon completion return
* the given result
*
* @param task the task to submit
* @param result the result to return
* @return a Future representing pending completion of the task,
* and whose <tt>get()</tt> method will return the given result
* upon completion.
* @throws RejectedExecutionException if task cannot be scheduled
* for execution
* @throws NullPointerException if task null
*/
<T> Future<T> submit(Runnable task, T result);
/**
* Submits a Runnable task for execution and returns a Future
* representing that task.
*
* @param task the task to submit
* @return a Future representing pending completion of the task,
* and whose <tt>get()</tt> method will return <tt>null</tt>
* upon completion.
* @throws RejectedExecutionException if task cannot be scheduled
* for execution
* @throws NullPointerException if task 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<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<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 empty
* @throws ExecutionException if no task successfully completes
* @throws RejectedExecutionException if tasks cannot be scheduled
* for execution
*/
<T> T invokeAny(Collection<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<Callable<T>> tasks,
long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException;
}
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