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 their results
     * when all complete.
     * 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 their results
     * when all complete or the timeout expires, whichever happens first.
     * 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 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:	1.24
Committed:	Sun Jan 11 23:19:55 2004 UTC (20 years, 4 months ago) by dl
Branch:	MAIN
Changes since 1.23:	+1 -1 lines
Log Message:	formatting; grammar
#	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	1.24	* 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			* one or more asynchronous tasks. <p>
18	dl	1.17	*
19	dl	1.7	* An <tt>ExecutorService</tt> can be shut down, which will cause it
20			* to stop accepting new tasks. After being shut down, the executor
21			* will eventually terminate, at which point no tasks are actively
22	dl	1.1	* executing, no tasks are awaiting execution, and no new tasks can be
23			* submitted.
24			*
25	dl	1.20	* <p> Method <tt>submit</tt> extends base method {@link
26			* Executor#execute} by creating and returning a {@link Future} that
27			* can be used to cancel execution and/or wait for completion.
28			* Methods <tt>invokeAny</tt> and <tt>invokeAll</tt> perform the most
29			* commonly useful forms of bulk execution, executing a collection of
30			* tasks and then waiting for at least one, or all, to
31			* complete. (Class {@link ExecutorCompletionService} can be used to
32			* write customized variants of these methods.)
33	dl	1.17	*
34	dl	1.7	* <p>The {@link Executors} class provides factory methods for the
35			* executor services provided in this package.
36	dl	1.1	*
37	dl	1.23	* <h3>Usage Example</h3>
38			*
39			* Here is a sketch of a network service in which threads in a thread
40			* pool service incoming requests. It uses the preconfigured {@link
41			* Executors#newFixedThreadPool} factory method:
42			*
43			* <pre>
44			* class NetworkService {
45			* private final ServerSocket serverSocket;
46			* private final ExecutorService pool;
47			*
48			* public NetworkService(int port, int poolSize) throws IOException {
49			* serverSocket = new ServerSocket(port);
50			* pool = Executors.newFixedThreadPool(poolSize);
51			* }
52			*
53			* public void serve() {
54			* try {
55			* for (;;) {
56			* pool.execute(new Handler(serverSocket.accept()));
57			* }
58			* } catch (IOException ex) {
59			* pool.shutdown();
60			* }
61			* }
62			* }
63			*
64			* class Handler implements Runnable {
65			* private final Socket socket;
66			* Handler(Socket socket) { this.socket = socket; }
67			* public void run() {
68			* // read and service request
69			* }
70			* }
71			* </pre>
72	dl	1.1	* @since 1.5
73	dl	1.5	* @author Doug Lea
74	dl	1.1	*/
75			public interface ExecutorService extends Executor {
76	tim	1.8
77	dl	1.17	/**
78			* Initiates an orderly shutdown in which previously submitted
79			* tasks are executed, but no new tasks will be
80			* accepted. Invocation has no additional effect if already shut
81			* down.
82			* @throws SecurityException if a security manager exists and
83			* shutting down this ExecutorService may manipulate threads that
84			* the caller is not permitted to modify because it does not hold
85			* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
86			* or the security manager's <tt>checkAccess</tt> method denies access.
87			*/
88			void shutdown();
89
90			/**
91			* Attempts to stop all actively executing tasks, halts the
92			* processing of waiting tasks, and returns a list of the tasks that were
93			* awaiting execution.
94			*
95			* <p>There are no guarantees beyond best-effort attempts to stop
96			* processing actively executing tasks. For example, typical
97			* implementations will cancel via {@link Thread#interrupt}, so if any
98			* tasks mask or fail to respond to interrupts, they may never terminate.
99			*
100			* @return list of tasks that never commenced execution
101			* @throws SecurityException if a security manager exists and
102			* shutting down this ExecutorService may manipulate threads that
103			* the caller is not permitted to modify because it does not hold
104			* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
105			* or the security manager's <tt>checkAccess</tt> method denies access.
106			*/
107			List<Runnable> shutdownNow();
108
109			/**
110			* Returns <tt>true</tt> if this executor has been shut down.
111			*
112			* @return <tt>true</tt> if this executor has been shut down
113			*/
114			boolean isShutdown();
115
116			/**
117			* Returns <tt>true</tt> if all tasks have completed following shut down.
118			* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
119			* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
120			*
121			* @return <tt>true</tt> if all tasks have completed following shut down
122			*/
123			boolean isTerminated();
124
125			/**
126			* Blocks until all tasks have completed execution after a shutdown
127			* request, or the timeout occurs, or the current thread is
128			* interrupted, whichever happens first.
129			*
130			* @param timeout the maximum time to wait
131			* @param unit the time unit of the timeout argument
132			* @return <tt>true</tt> if this executor terminated and <tt>false</tt>
133			* if the timeout elapsed before termination
134			* @throws InterruptedException if interrupted while waiting
135			*/
136			boolean awaitTermination(long timeout, TimeUnit unit)
137			throws InterruptedException;
138
139
140	tim	1.8	/**
141			* Submits a value-returning task for execution and returns a Future
142	dl	1.19	* representing the pending results of the task.
143	tim	1.8	*
144	dl	1.19	* <p>
145	dl	1.20	* If you would like to immediately block waiting
146	dl	1.19	* for a task, you can use constructions of the form
147			* <tt>result = exec.submit(aCallable).get();</tt>
148	dl	1.20	*
149			* <p> Note: The {@link Executors} class includes a set of methods
150			* that can convert some other common closure-like objects,
151			* for example, {@link java.security.PrivilegedAction} to
152			* {@link Callable} form so they can be submitted.
153			*
154	tim	1.8	* @param task the task to submit
155			* @return a Future representing pending completion of the task
156			* @throws RejectedExecutionException if task cannot be scheduled
157			* for execution
158	dl	1.20	* @throws NullPointerException if task null
159	tim	1.8	*/
160			<T> Future<T> submit(Callable<T> task);
161
162			/**
163	dl	1.18	* Submits a Runnable task for execution and returns a Future
164	dl	1.20	* representing that task that will upon completion return
165			* the given result
166			*
167			* @param task the task to submit
168			* @param result the result to return
169			* @return a Future representing pending completion of the task,
170			* and whose <tt>get()</tt> method will return the given result
171			* upon completion.
172			* @throws RejectedExecutionException if task cannot be scheduled
173			* for execution
174			* @throws NullPointerException if task null
175			*/
176			<T> Future<T> submit(Runnable task, T result);
177
178			/**
179			* Submits a Runnable task for execution and returns a Future
180	dl	1.18	* representing that task.
181	dl	1.1	*
182	dl	1.17	* @param task the task to submit
183	dl	1.18	* @return a Future representing pending completion of the task,
184			* and whose <tt>get()</tt> method will return <tt>null</tt>
185			* upon completion.
186	dl	1.17	* @throws RejectedExecutionException if task cannot be scheduled
187			* for execution
188	dl	1.20	* @throws NullPointerException if task null
189	dl	1.1	*/
190	dl	1.18	Future<?> submit(Runnable task);
191	dl	1.15
192	dl	1.11	/**
193	dl	1.17	* Executes the given tasks, returning their results
194	dl	1.15	* when all complete.
195	dl	1.12	* Note that a <em>completed</em> task could have
196			* terminated either normally or by throwing an exception.
197	dl	1.21	* The results of this method are undefined if the given
198			* collection is modified while this operation is in progress.
199	dl	1.11	* @param tasks the collection of tasks
200	dl	1.13	* @return A list of Futures representing the tasks, in the same
201	dl	1.21	* sequential order as produced by the iterator for the given task
202			* list, each of which has completed.
203	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
204			* which case unfinished tasks are cancelled.
205	dl	1.13	* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
206			* @throws RejectedExecutionException if any task cannot be scheduled
207			* for execution
208	dl	1.11	*/
209	dl	1.15
210	dl	1.16	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
211	dl	1.11	throws InterruptedException;
212
213			/**
214	dl	1.17	* Executes the given tasks, returning their results
215	dl	1.15	* when all complete or the timeout expires, whichever happens first.
216	dl	1.11	* Upon return, tasks that have not completed are cancelled.
217	dl	1.12	* Note that a <em>completed</em> task could have
218			* terminated either normally or by throwing an exception.
219	dl	1.21	* The results of this method are undefined if the given
220			* collection is modified while this operation is in progress.
221	dl	1.11	* @param tasks the collection of tasks
222			* @param timeout the maximum time to wait
223	dl	1.15	* @param unit the time unit of the timeout argument
224	dl	1.13	* @return A list of Futures representing the tasks, in the same
225	dl	1.21	* sequential order as as produced by the iterator for the given
226			* task list. If the operation did not time out, each task will
227			* have completed. If it did time out, some of thiese tasks will
228			* not have completed.
229	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
230			* which case unfinished tasks are cancelled.
231	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
232	dl	1.15	* unit are <tt>null</tt>
233	dl	1.13	* @throws RejectedExecutionException if any task cannot be scheduled
234			* for execution
235	dl	1.11	*/
236	dl	1.16	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
237	dl	1.18	long timeout, TimeUnit unit)
238	dl	1.11	throws InterruptedException;
239
240			/**
241	dl	1.17	* Executes the given tasks, returning the result
242	dl	1.15	* of one that has completed successfully (i.e., without throwing
243			* an exception), if any do. Upon normal or exceptional return,
244			* tasks that have not completed are cancelled.
245	dl	1.21	* The results of this method are undefined if the given
246			* collection is modified while this operation is in progress.
247	dl	1.11	* @param tasks the collection of tasks
248	dl	1.15	* @return The result returned by one of the tasks.
249			* @throws InterruptedException if interrupted while waiting
250			* @throws NullPointerException if tasks or any of its elements
251			* are <tt>null</tt>
252			* @throws IllegalArgumentException if tasks empty
253			* @throws ExecutionException if no task successfully completes
254			* @throws RejectedExecutionException if tasks cannot be scheduled
255	dl	1.13	* for execution
256	dl	1.11	*/
257	dl	1.15	<T> T invokeAny(Collection<Callable<T>> tasks)
258			throws InterruptedException, ExecutionException;
259	dl	1.11
260			/**
261	dl	1.17	* Executes the given tasks, returning the result
262	dl	1.15	* of one that has completed successfully (i.e., without throwing
263			* an exception), if any do before the given timeout elapses.
264			* Upon normal or exceptional return, tasks that have not
265			* completed are cancelled.
266	dl	1.21	* The results of this method are undefined if the given
267			* collection is modified while this operation is in progress.
268	dl	1.11	* @param tasks the collection of tasks
269			* @param timeout the maximum time to wait
270			* @param unit the time unit of the timeout argument
271	dl	1.15	* @return The result returned by one of the tasks.
272			* @throws InterruptedException if interrupted while waiting
273	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
274	dl	1.15	* unit are <tt>null</tt>
275			* @throws TimeoutException if the given timeout elapses before
276			* any task successfully completes
277			* @throws ExecutionException if no task successfully completes
278			* @throws RejectedExecutionException if tasks cannot be scheduled
279	dl	1.13	* for execution
280	dl	1.11	*/
281	dl	1.15	<T> T invokeAny(Collection<Callable<T>> tasks,
282			long timeout, TimeUnit unit)
283			throws InterruptedException, ExecutionException, TimeoutException;
284	dl	1.3
285	dl	1.1	}