util/concurrent/ExecutorService.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.concurrent.*; // for javadoc (till 6280605 is fixed)
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>
 *
 * Memory visibility effects: State changes to a <tt>Runnable</tt> or
 * <tt>Callable</tt> object made prior to submission to an
 * <tt>Executor</tt> <a
 * href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
 * its execution, and state changes to objects returned from a
 * <tt>Callable</tt> <i>happen-before</i> that object is returned to
 * a thread which calls <tt>Future.get()</tt> to retrieve that result.
 *
 * @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;
}
Revision:	1.41
Committed:	Fri Sep 2 01:10:52 2005 UTC (18 years, 9 months ago) by brian
Branch:	MAIN
Changes since 1.40:	+1 -1 lines
Log Message:	Formatting tweaks to happens-before markup
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain, as explained at
4	* http://creativecommons.org/licenses/publicdomain
5	*/
6
7	package java.util.concurrent;
8	import java.util.concurrent.*; // for javadoc (till 6280605 is fixed)
9	import java.util.List;
10	import java.util.Collection;
11	import java.security.PrivilegedAction;
12	import java.security.PrivilegedExceptionAction;
13
14	/**
15	* An {@link Executor} that provides methods to manage termination and
16	* methods that can produce a {@link Future} for tracking progress of
17	* one or more asynchronous tasks.
18	*
19	* <p>
20	* An <tt>ExecutorService</tt> can be shut down, which will cause it
21	* to stop accepting new tasks. After being shut down, the executor
22	* will eventually terminate, at which point no tasks are actively
23	* executing, no tasks are awaiting execution, and no new tasks can be
24	* submitted.
25	*
26	* <p> Method <tt>submit</tt> extends base method {@link
27	* Executor#execute} by creating and returning a {@link Future} that
28	* can be used to cancel execution and/or wait for completion.
29	* Methods <tt>invokeAny</tt> and <tt>invokeAll</tt> perform the most
30	* commonly useful forms of bulk execution, executing a collection of
31	* tasks and then waiting for at least one, or all, to
32	* complete. (Class {@link ExecutorCompletionService} can be used to
33	* write customized variants of these methods.)
34	*
35	* <p>The {@link Executors} class provides factory methods for the
36	* executor services provided in this package.
37	*
38	* <h3>Usage Example</h3>
39	*
40	* Here is a sketch of a network service in which threads in a thread
41	* pool service incoming requests. It uses the preconfigured {@link
42	* Executors#newFixedThreadPool} factory method:
43	*
44	* <pre>
45	* class NetworkService {
46	* private final ServerSocket serverSocket;
47	* private final ExecutorService pool;
48	*
49	* public NetworkService(int port, int poolSize)
50	* throws IOException {
51	* serverSocket = new ServerSocket(port);
52	* pool = Executors.newFixedThreadPool(poolSize);
53	* }
54	*
55	* public void serve() {
56	* try {
57	* for (;;) {
58	* pool.execute(new Handler(serverSocket.accept()));
59	* }
60	* } catch (IOException ex) {
61	* pool.shutdown();
62	* }
63	* }
64	* }
65	*
66	* class Handler implements Runnable {
67	* private final Socket socket;
68	* Handler(Socket socket) { this.socket = socket; }
69	* public void run() {
70	* // read and service request
71	* }
72	* }
73	* </pre>
74	*
75	* Memory visibility effects: State changes to a <tt>Runnable</tt> or
76	* <tt>Callable</tt> object made prior to submission to an
77	* <tt>Executor</tt> <a
78	* href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
79	* its execution, and state changes to objects returned from a
80	* <tt>Callable</tt> <i>happen-before</i> that object is returned to
81	* a thread which calls <tt>Future.get()</tt> to retrieve that result.
82	*
83	* @since 1.5
84	* @author Doug Lea
85	*/
86	public interface ExecutorService extends Executor {
87
88	/**
89	* Initiates an orderly shutdown in which previously submitted
90	* tasks are executed, but no new tasks will be accepted.
91	* Invocation has no additional effect if already shut down.
92	*
93	* @throws SecurityException if a security manager exists and
94	* shutting down this ExecutorService may manipulate
95	* threads that the caller is not permitted to modify
96	* because it does not hold {@link
97	* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
98	* or the security manager's <tt>checkAccess</tt> method
99	* denies access.
100	*/
101	void shutdown();
102
103	/**
104	* Attempts to stop all actively executing tasks, halts the
105	* processing of waiting tasks, and returns a list of the tasks that were
106	* awaiting execution.
107	*
108	* <p>There are no guarantees beyond best-effort attempts to stop
109	* processing actively executing tasks. For example, typical
110	* implementations will cancel via {@link Thread#interrupt}, so any
111	* task that fails to respond to interrupts may never terminate.
112	*
113	* @return list of tasks that never commenced execution
114	* @throws SecurityException if a security manager exists and
115	* shutting down this ExecutorService may manipulate
116	* threads that the caller is not permitted to modify
117	* because it does not hold {@link
118	* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
119	* or the security manager's <tt>checkAccess</tt> method
120	* denies access.
121	*/
122	List<Runnable> shutdownNow();
123
124	/**
125	* Returns <tt>true</tt> if this executor has been shut down.
126	*
127	* @return <tt>true</tt> if this executor has been shut down
128	*/
129	boolean isShutdown();
130
131	/**
132	* Returns <tt>true</tt> if all tasks have completed following shut down.
133	* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
134	* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
135	*
136	* @return <tt>true</tt> if all tasks have completed following shut down
137	*/
138	boolean isTerminated();
139
140	/**
141	* Blocks until all tasks have completed execution after a shutdown
142	* request, or the timeout occurs, or the current thread is
143	* interrupted, whichever happens first.
144	*
145	* @param timeout the maximum time to wait
146	* @param unit the time unit of the timeout argument
147	* @return <tt>true</tt> if this executor terminated and
148	* <tt>false</tt> if the timeout elapsed before termination
149	* @throws InterruptedException if interrupted while waiting
150	*/
151	boolean awaitTermination(long timeout, TimeUnit unit)
152	throws InterruptedException;
153
154
155	/**
156	* Submits a value-returning task for execution and returns a
157	* Future representing the pending results of the task. The
158	* Future's <tt>get</tt> method will return the task's result upon
159	* successful completion.
160	*
161	* <p>
162	* If you would like to immediately block waiting
163	* for a task, you can use constructions of the form
164	* <tt>result = exec.submit(aCallable).get();</tt>
165	*
166	* <p> Note: The {@link Executors} class includes a set of methods
167	* that can convert some other common closure-like objects,
168	* for example, {@link java.security.PrivilegedAction} to
169	* {@link Callable} form so they can be submitted.
170	*
171	* @param task the task to submit
172	* @return a Future representing pending completion of the task
173	* @throws RejectedExecutionException if the task cannot be
174	* scheduled for execution
175	* @throws NullPointerException if the task is null
176	*/
177	<T> Future<T> submit(Callable<T> task);
178
179	/**
180	* Submits a Runnable task for execution and returns a Future
181	* representing that task. The Future's <tt>get</tt> method will
182	* return the given result upon successful completion.
183	*
184	* @param task the task to submit
185	* @param result the result to return
186	* @return a Future representing pending completion of the task
187	* @throws RejectedExecutionException if the task cannot be
188	* scheduled for execution
189	* @throws NullPointerException if the task is null
190	*/
191	<T> Future<T> submit(Runnable task, T result);
192
193	/**
194	* Submits a Runnable task for execution and returns a Future
195	* representing that task. The Future's <tt>get</tt> method will
196	* return <tt>null</tt> upon <em>successful</em> completion.
197	*
198	* @param task the task to submit
199	* @return a Future representing pending completion of the task
200	* @throws RejectedExecutionException if the task cannot be
201	* scheduled for execution
202	* @throws NullPointerException if the task is null
203	*/
204	Future<?> submit(Runnable task);
205
206	/**
207	* Executes the given tasks, returning a list of Futures holding
208	* their status and results when all complete.
209	* {@link Future#isDone} is <tt>true</tt> for each
210	* element of the returned list.
211	* Note that a <em>completed</em> task could have
212	* terminated either normally or by throwing an exception.
213	* The results of this method are undefined if the given
214	* collection is modified while this operation is in progress.
215	*
216	* @param tasks the collection of tasks
217	* @return A list of Futures representing the tasks, in the same
218	* sequential order as produced by the iterator for the
219	* given task list, each of which has completed.
220	* @throws InterruptedException if interrupted while waiting, in
221	* which case unfinished tasks are cancelled.
222	* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
223	* @throws RejectedExecutionException if any task cannot be
224	* scheduled for execution
225	*/
226
227	<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
228	throws InterruptedException;
229
230	/**
231	* Executes the given tasks, returning a list of Futures holding
232	* their status and results
233	* when all complete or the timeout expires, whichever happens first.
234	* {@link Future#isDone} is <tt>true</tt> for each
235	* element of the returned list.
236	* Upon return, tasks that have not completed are cancelled.
237	* Note that a <em>completed</em> task could have
238	* terminated either normally or by throwing an exception.
239	* The results of this method are undefined if the given
240	* collection is modified while this operation is in progress.
241	*
242	* @param tasks the collection of tasks
243	* @param timeout the maximum time to wait
244	* @param unit the time unit of the timeout argument
245	* @return a list of Futures representing the tasks, in the same
246	* sequential order as produced by the iterator for the
247	* given task list. If the operation did not time out,
248	* each task will have completed. If it did time out, some
249	* of these tasks will not have completed.
250	* @throws InterruptedException if interrupted while waiting, in
251	* which case unfinished tasks are cancelled
252	* @throws NullPointerException if tasks, any of its elements, or
253	* unit are <tt>null</tt>
254	* @throws RejectedExecutionException if any task cannot be scheduled
255	* for execution
256	*/
257	<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
258	long timeout, TimeUnit unit)
259	throws InterruptedException;
260
261	/**
262	* Executes the given tasks, returning the result
263	* of one that has completed successfully (i.e., without throwing
264	* an exception), if any do. Upon normal or exceptional return,
265	* tasks that have not completed are cancelled.
266	* The results of this method are undefined if the given
267	* collection is modified while this operation is in progress.
268	*
269	* @param tasks the collection of tasks
270	* @return the result returned by one of the tasks
271	* @throws InterruptedException if interrupted while waiting
272	* @throws NullPointerException if tasks or any of its elements
273	* are <tt>null</tt>
274	* @throws IllegalArgumentException if tasks is empty
275	* @throws ExecutionException if no task successfully completes
276	* @throws RejectedExecutionException if tasks cannot be scheduled
277	* for execution
278	*/
279	<T> T invokeAny(Collection<? extends Callable<T>> tasks)
280	throws InterruptedException, ExecutionException;
281
282	/**
283	* Executes the given tasks, returning the result
284	* of one that has completed successfully (i.e., without throwing
285	* an exception), if any do before the given timeout elapses.
286	* Upon normal or exceptional return, tasks that have not
287	* completed are cancelled.
288	* The results of this method are undefined if the given
289	* collection is modified while this operation is in progress.
290	*
291	* @param tasks the collection of tasks
292	* @param timeout the maximum time to wait
293	* @param unit the time unit of the timeout argument
294	* @return the result returned by one of the tasks.
295	* @throws InterruptedException if interrupted while waiting
296	* @throws NullPointerException if tasks, any of its elements, or
297	* unit are <tt>null</tt>
298	* @throws TimeoutException if the given timeout elapses before
299	* any task successfully completes
300	* @throws ExecutionException if no task successfully completes
301	* @throws RejectedExecutionException if tasks cannot be scheduled
302	* for execution
303	*/
304	<T> T invokeAny(Collection<? extends Callable<T>> tasks,
305	long timeout, TimeUnit unit)
306	throws InterruptedException, ExecutionException, TimeoutException;
307	}