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.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. To wait "forever"
     * use <tt>awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS)</tt>.
     *
     * @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, and whose
     * <<tt>get</tt> method will return the given result upon
     * <em>successful</em> 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 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 successful 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 successful 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 successful 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;

}
Revision:	1.30
Committed:	Tue Mar 1 01:27:46 2005 UTC (19 years, 3 months ago) by dl
Branch:	MAIN
Changes since 1.29:	+9 -7 lines
Log Message:	Documentation improvements
#	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
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) throws IOException {
50	* serverSocket = new ServerSocket(port);
51	* pool = Executors.newFixedThreadPool(poolSize);
52	* }
53	*
54	* public void serve() {
55	* try {
56	* for (;;) {
57	* pool.execute(new Handler(serverSocket.accept()));
58	* }
59	* } catch (IOException ex) {
60	* pool.shutdown();
61	* }
62	* }
63	* }
64	*
65	* class Handler implements Runnable {
66	* private final Socket socket;
67	* Handler(Socket socket) { this.socket = socket; }
68	* public void run() {
69	* // read and service request
70	* }
71	* }
72	* </pre>
73	* @since 1.5
74	* @author Doug Lea
75	*/
76	public interface ExecutorService extends Executor {
77
78	/**
79	* Initiates an orderly shutdown in which previously submitted
80	* tasks are executed, but no new tasks will be
81	* accepted. Invocation has no additional effect if already shut
82	* down.
83	* @throws SecurityException if a security manager exists and
84	* shutting down this ExecutorService may manipulate threads that
85	* the caller is not permitted to modify because it does not hold
86	* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
87	* or the security manager's <tt>checkAccess</tt> method denies access.
88	*/
89	void shutdown();
90
91	/**
92	* Attempts to stop all actively executing tasks, halts the
93	* processing of waiting tasks, and returns a list of the tasks that were
94	* awaiting execution.
95	*
96	* <p>There are no guarantees beyond best-effort attempts to stop
97	* processing actively executing tasks. For example, typical
98	* implementations will cancel via {@link Thread#interrupt}, so if any
99	* tasks mask or fail to respond to interrupts, they may never terminate.
100	*
101	* @return list of tasks that never commenced execution
102	* @throws SecurityException if a security manager exists and
103	* shutting down this ExecutorService may manipulate threads that
104	* the caller is not permitted to modify because it does not hold
105	* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
106	* or the security manager's <tt>checkAccess</tt> method denies access.
107	*/
108	List<Runnable> shutdownNow();
109
110	/**
111	* Returns <tt>true</tt> if this executor has been shut down.
112	*
113	* @return <tt>true</tt> if this executor has been shut down
114	*/
115	boolean isShutdown();
116
117	/**
118	* Returns <tt>true</tt> if all tasks have completed following shut down.
119	* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
120	* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
121	*
122	* @return <tt>true</tt> if all tasks have completed following shut down
123	*/
124	boolean isTerminated();
125
126	/**
127	* Blocks until all tasks have completed execution after a shutdown
128	* request, or the timeout occurs, or the current thread is
129	* interrupted, whichever happens first. To wait "forever"
130	* use <tt>awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS)</tt>.
131	*
132	* @param timeout the maximum time to wait
133	* @param unit the time unit of the timeout argument
134	* @return <tt>true</tt> if this executor terminated and <tt>false</tt>
135	* if the timeout elapsed before termination
136	* @throws InterruptedException if interrupted while waiting
137	*/
138	boolean awaitTermination(long timeout, TimeUnit unit)
139	throws InterruptedException;
140
141
142	/**
143	* Submits a value-returning task for execution and returns a
144	* Future representing the pending results of the task, and whose
145	* <<tt>get</tt> method will return the given result upon
146	* <em>successful</em> completion.
147	*
148	* <p>
149	* If you would like to immediately block waiting
150	* for a task, you can use constructions of the form
151	* <tt>result = exec.submit(aCallable).get();</tt>
152	*
153	* <p> Note: The {@link Executors} class includes a set of methods
154	* that can convert some other common closure-like objects,
155	* for example, {@link java.security.PrivilegedAction} to
156	* {@link Callable} form so they can be submitted.
157	*
158	* @param task the task to submit
159	* @return a Future representing pending completion of the task
160	* @throws RejectedExecutionException if task cannot be scheduled
161	* for execution
162	* @throws NullPointerException if task null
163	*/
164	<T> Future<T> submit(Callable<T> task);
165
166	/**
167	* Submits a Runnable task for execution and returns a Future
168	* representing that task that will upon successful completion
169	* return the given result.
170	*
171	* @param task the task to submit
172	* @param result the result to return
173	* @return a Future representing pending completion of the task,
174	* and whose <tt>get()</tt> method will return the given result
175	* upon successful completion.
176	* @throws RejectedExecutionException if task cannot be scheduled
177	* for execution
178	* @throws NullPointerException if task null
179	*/
180	<T> Future<T> submit(Runnable task, T result);
181
182	/**
183	* Submits a Runnable task for execution and returns a Future
184	* representing that task.
185	*
186	* @param task the task to submit
187	* @return a Future representing pending completion of the task,
188	* and whose <tt>get()</tt> method will return <tt>null</tt>
189	* upon successful completion.
190	* @throws RejectedExecutionException if task cannot be scheduled
191	* for execution
192	* @throws NullPointerException if task null
193	*/
194	Future<?> submit(Runnable task);
195
196	/**
197	* Executes the given tasks, returning a list of Futures holding
198	* their status and results when all complete.
199	* {@link Future#isDone} is <tt>true</tt> for each
200	* element of the returned list.
201	* Note that a <em>completed</em> task could have
202	* terminated either normally or by throwing an exception.
203	* The results of this method are undefined if the given
204	* collection is modified while this operation is in progress.
205	* @param tasks the collection of tasks
206	* @return A list of Futures representing the tasks, in the same
207	* sequential order as produced by the iterator for the given task
208	* list, each of which has completed.
209	* @throws InterruptedException if interrupted while waiting, in
210	* which case unfinished tasks are cancelled.
211	* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
212	* @throws RejectedExecutionException if any task cannot be scheduled
213	* for execution
214	*/
215
216	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
217	throws InterruptedException;
218
219	/**
220	* Executes the given tasks, returning a list of Futures holding
221	* their status and results
222	* when all complete or the timeout expires, whichever happens first.
223	* {@link Future#isDone} is <tt>true</tt> for each
224	* element of the returned list.
225	* Upon return, tasks that have not completed are cancelled.
226	* Note that a <em>completed</em> task could have
227	* terminated either normally or by throwing an exception.
228	* The results of this method are undefined if the given
229	* collection is modified while this operation is in progress.
230	* @param tasks the collection of tasks
231	* @param timeout the maximum time to wait
232	* @param unit the time unit of the timeout argument
233	* @return A list of Futures representing the tasks, in the same
234	* sequential order as produced by the iterator for the given
235	* task list. If the operation did not time out, each task will
236	* have completed. If it did time out, some of these tasks will
237	* not have completed.
238	* @throws InterruptedException if interrupted while waiting, in
239	* which case unfinished tasks are cancelled.
240	* @throws NullPointerException if tasks, any of its elements, or
241	* unit are <tt>null</tt>
242	* @throws RejectedExecutionException if any task cannot be scheduled
243	* for execution
244	*/
245	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
246	long timeout, TimeUnit unit)
247	throws InterruptedException;
248
249	/**
250	* Executes the given tasks, returning the result
251	* of one that has completed successfully (i.e., without throwing
252	* an exception), if any do. Upon normal or exceptional return,
253	* tasks that have not completed are cancelled.
254	* The results of this method are undefined if the given
255	* collection is modified while this operation is in progress.
256	* @param tasks the collection of tasks
257	* @return The result returned by one of the tasks.
258	* @throws InterruptedException if interrupted while waiting
259	* @throws NullPointerException if tasks or any of its elements
260	* are <tt>null</tt>
261	* @throws IllegalArgumentException if tasks empty
262	* @throws ExecutionException if no task successfully completes
263	* @throws RejectedExecutionException if tasks cannot be scheduled
264	* for execution
265	*/
266	<T> T invokeAny(Collection<Callable<T>> tasks)
267	throws InterruptedException, ExecutionException;
268
269	/**
270	* Executes the given tasks, returning the result
271	* of one that has completed successfully (i.e., without throwing
272	* an exception), if any do before the given timeout elapses.
273	* Upon normal or exceptional return, tasks that have not
274	* completed are cancelled.
275	* The results of this method are undefined if the given
276	* collection is modified while this operation is in progress.
277	* @param tasks the collection of tasks
278	* @param timeout the maximum time to wait
279	* @param unit the time unit of the timeout argument
280	* @return The result returned by one of the tasks.
281	* @throws InterruptedException if interrupted while waiting
282	* @throws NullPointerException if tasks, any of its elements, or
283	* unit are <tt>null</tt>
284	* @throws TimeoutException if the given timeout elapses before
285	* any task successfully completes
286	* @throws ExecutionException if no task successfully completes
287	* @throws RejectedExecutionException if tasks cannot be scheduled
288	* for execution
289	*/
290	<T> T invokeAny(Collection<Callable<T>> tasks,
291	long timeout, TimeUnit unit)
292	throws InterruptedException, ExecutionException, TimeoutException;
293
294	}