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.
     *
     * @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 thiese 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:	1.27
Committed:	Sat Apr 10 14:25:24 2004 UTC (20 years, 1 month ago) by dl
Branch:	MAIN
Changes since 1.26:	+8 -3 lines
Log Message:	Documentation improvements
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.22	* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5	dl	1.1	*/
6
7			package java.util.concurrent;
8
9			import java.util.List;
10	dl	1.15	import java.util.Collection;
11	tim	1.8	import java.security.PrivilegedAction;
12			import java.security.PrivilegedExceptionAction;
13	dl	1.1
14			/**
15	dl	1.25	* An {@link Executor} that provides methods to manage termination and
16	dl	1.20	* methods that can produce a {@link Future} for tracking progress of
17	dl	1.25	* one or more asynchronous tasks.
18	dl	1.17	*
19	dl	1.25	* <p>
20	dl	1.7	* 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	dl	1.1	* executing, no tasks are awaiting execution, and no new tasks can be
24			* submitted.
25			*
26	dl	1.20	* <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	dl	1.17	*
35	dl	1.7	* <p>The {@link Executors} class provides factory methods for the
36			* executor services provided in this package.
37	dl	1.1	*
38	dl	1.23	* <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	dl	1.1	* @since 1.5
74	dl	1.5	* @author Doug Lea
75	dl	1.1	*/
76			public interface ExecutorService extends Executor {
77	tim	1.8
78	dl	1.17	/**
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.
130			*
131			* @param timeout the maximum time to wait
132			* @param unit the time unit of the timeout argument
133			* @return <tt>true</tt> if this executor terminated and <tt>false</tt>
134			* if the timeout elapsed before termination
135			* @throws InterruptedException if interrupted while waiting
136			*/
137			boolean awaitTermination(long timeout, TimeUnit unit)
138			throws InterruptedException;
139
140
141	tim	1.8	/**
142			* Submits a value-returning task for execution and returns a Future
143	dl	1.19	* representing the pending results of the task.
144	tim	1.8	*
145	dl	1.19	* <p>
146	dl	1.20	* If you would like to immediately block waiting
147	dl	1.19	* for a task, you can use constructions of the form
148			* <tt>result = exec.submit(aCallable).get();</tt>
149	dl	1.20	*
150			* <p> Note: The {@link Executors} class includes a set of methods
151			* that can convert some other common closure-like objects,
152			* for example, {@link java.security.PrivilegedAction} to
153			* {@link Callable} form so they can be submitted.
154			*
155	tim	1.8	* @param task the task to submit
156			* @return a Future representing pending completion of the task
157			* @throws RejectedExecutionException if task cannot be scheduled
158			* for execution
159	dl	1.20	* @throws NullPointerException if task null
160	tim	1.8	*/
161			<T> Future<T> submit(Callable<T> task);
162
163			/**
164	dl	1.18	* Submits a Runnable task for execution and returns a Future
165	dl	1.20	* representing that task that will upon completion return
166			* the given result
167			*
168			* @param task the task to submit
169			* @param result the result to return
170			* @return a Future representing pending completion of the task,
171			* and whose <tt>get()</tt> method will return the given result
172			* upon completion.
173			* @throws RejectedExecutionException if task cannot be scheduled
174			* for execution
175			* @throws NullPointerException if task null
176			*/
177			<T> Future<T> submit(Runnable task, T result);
178
179			/**
180			* Submits a Runnable task for execution and returns a Future
181	dl	1.18	* representing that task.
182	dl	1.1	*
183	dl	1.17	* @param task the task to submit
184	dl	1.18	* @return a Future representing pending completion of the task,
185			* and whose <tt>get()</tt> method will return <tt>null</tt>
186			* upon completion.
187	dl	1.17	* @throws RejectedExecutionException if task cannot be scheduled
188			* for execution
189	dl	1.20	* @throws NullPointerException if task null
190	dl	1.1	*/
191	dl	1.18	Future<?> submit(Runnable task);
192	dl	1.15
193	dl	1.11	/**
194	dl	1.27	* Executes the given tasks, returning a list of Futures holding
195			* their status and results when all complete.
196			* {@link Future#isDone} is <tt>true</tt> for each
197			* element of the returned list.
198	dl	1.12	* Note that a <em>completed</em> task could have
199			* terminated either normally or by throwing an exception.
200	dl	1.21	* The results of this method are undefined if the given
201			* collection is modified while this operation is in progress.
202	dl	1.11	* @param tasks the collection of tasks
203	dl	1.13	* @return A list of Futures representing the tasks, in the same
204	dl	1.21	* sequential order as produced by the iterator for the given task
205			* list, each of which has completed.
206	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
207			* which case unfinished tasks are cancelled.
208	dl	1.13	* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
209			* @throws RejectedExecutionException if any task cannot be scheduled
210			* for execution
211	dl	1.11	*/
212	dl	1.15
213	dl	1.16	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
214	dl	1.11	throws InterruptedException;
215
216			/**
217	dl	1.27	* Executes the given tasks, returning a list of Futures holding
218			* their status and results
219	dl	1.15	* when all complete or the timeout expires, whichever happens first.
220	dl	1.27	* {@link Future#isDone} is <tt>true</tt> for each
221			* element of the returned list.
222	dl	1.11	* Upon return, tasks that have not completed are cancelled.
223	dl	1.12	* Note that a <em>completed</em> task could have
224			* terminated either normally or by throwing an exception.
225	dl	1.21	* The results of this method are undefined if the given
226			* collection is modified while this operation is in progress.
227	dl	1.11	* @param tasks the collection of tasks
228			* @param timeout the maximum time to wait
229	dl	1.15	* @param unit the time unit of the timeout argument
230	dl	1.13	* @return A list of Futures representing the tasks, in the same
231	dl	1.26	* sequential order as produced by the iterator for the given
232	dl	1.21	* task list. If the operation did not time out, each task will
233			* have completed. If it did time out, some of thiese tasks will
234			* not have completed.
235	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
236			* which case unfinished tasks are cancelled.
237	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
238	dl	1.15	* unit are <tt>null</tt>
239	dl	1.13	* @throws RejectedExecutionException if any task cannot be scheduled
240			* for execution
241	dl	1.11	*/
242	dl	1.16	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
243	dl	1.18	long timeout, TimeUnit unit)
244	dl	1.11	throws InterruptedException;
245
246			/**
247	dl	1.17	* Executes the given tasks, returning the result
248	dl	1.15	* of one that has completed successfully (i.e., without throwing
249			* an exception), if any do. Upon normal or exceptional return,
250			* tasks that have not completed are cancelled.
251	dl	1.21	* The results of this method are undefined if the given
252			* collection is modified while this operation is in progress.
253	dl	1.11	* @param tasks the collection of tasks
254	dl	1.15	* @return The result returned by one of the tasks.
255			* @throws InterruptedException if interrupted while waiting
256			* @throws NullPointerException if tasks or any of its elements
257			* are <tt>null</tt>
258			* @throws IllegalArgumentException if tasks empty
259			* @throws ExecutionException if no task successfully completes
260			* @throws RejectedExecutionException if tasks cannot be scheduled
261	dl	1.13	* for execution
262	dl	1.11	*/
263	dl	1.15	<T> T invokeAny(Collection<Callable<T>> tasks)
264			throws InterruptedException, ExecutionException;
265	dl	1.11
266			/**
267	dl	1.17	* Executes the given tasks, returning the result
268	dl	1.15	* of one that has completed successfully (i.e., without throwing
269			* an exception), if any do before the given timeout elapses.
270			* Upon normal or exceptional return, tasks that have not
271			* completed are cancelled.
272	dl	1.21	* The results of this method are undefined if the given
273			* collection is modified while this operation is in progress.
274	dl	1.11	* @param tasks the collection of tasks
275			* @param timeout the maximum time to wait
276			* @param unit the time unit of the timeout argument
277	dl	1.15	* @return The result returned by one of the tasks.
278			* @throws InterruptedException if interrupted while waiting
279	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
280	dl	1.15	* unit are <tt>null</tt>
281			* @throws TimeoutException if the given timeout elapses before
282			* any task successfully completes
283			* @throws ExecutionException if no task successfully completes
284			* @throws RejectedExecutionException if tasks cannot be scheduled
285	dl	1.13	* for execution
286	dl	1.11	*/
287	dl	1.15	<T> T invokeAny(Collection<Callable<T>> tasks,
288			long timeout, TimeUnit unit)
289			throws InterruptedException, ExecutionException, TimeoutException;
290	dl	1.3
291	dl	1.1	}