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>
 *
 * <p>Memory consistency effects: Actions in a thread prior to the
 * submission of a {@code Runnable} or {@code Callable} task to an
 * {@code ExecutorService}
 * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
 * any actions taken by that task, which in turn <i>happen-before</i> the
 * result is retrieved via {@code Future.get()}.
 *
 * @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:	1.44
Committed:	Tue Feb 7 20:54:24 2006 UTC (18 years, 4 months ago) by jsr166
Branch:	MAIN
Changes since 1.43:	+0 -1 lines
Log Message:	6378729: Remove workaround for 6280605
#	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			import java.util.List;
9	dl	1.15	import java.util.Collection;
10	tim	1.8	import java.security.PrivilegedAction;
11			import java.security.PrivilegedExceptionAction;
12	dl	1.1
13			/**
14	dl	1.25	* An {@link Executor} that provides methods to manage termination and
15	dl	1.20	* methods that can produce a {@link Future} for tracking progress of
16	jsr166	1.33	* one or more asynchronous tasks.
17	dl	1.17	*
18	dl	1.25	* <p>
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	jsr166	1.37	* private final ServerSocket serverSocket;
46			* private final ExecutorService pool;
47	dl	1.23	*
48	jsr166	1.37	* public NetworkService(int port, int poolSize)
49			* throws IOException {
50			* serverSocket = new ServerSocket(port);
51			* pool = Executors.newFixedThreadPool(poolSize);
52			* }
53	jsr166	1.33	*
54	jsr166	1.37	* 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	dl	1.23	*
65	jsr166	1.37	* 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	dl	1.23	* }
72			* </pre>
73	brian	1.40	*
74	jsr166	1.43	* <p>Memory consistency effects: Actions in a thread prior to the
75			* submission of a {@code Runnable} or {@code Callable} task to an
76			* {@code ExecutorService}
77			* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
78			* any actions taken by that task, which in turn <i>happen-before</i> the
79			* result is retrieved via {@code Future.get()}.
80	brian	1.40	*
81	dl	1.1	* @since 1.5
82	dl	1.5	* @author Doug Lea
83	dl	1.1	*/
84			public interface ExecutorService extends Executor {
85	tim	1.8
86	dl	1.17	/**
87			* Initiates an orderly shutdown in which previously submitted
88	jsr166	1.37	* tasks are executed, but no new tasks will be accepted.
89			* Invocation has no additional effect if already shut down.
90			*
91	dl	1.17	* @throws SecurityException if a security manager exists and
92	jsr166	1.37	* shutting down this ExecutorService may manipulate
93			* threads that the caller is not permitted to modify
94			* because it does not hold {@link
95			* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
96			* or the security manager's <tt>checkAccess</tt> method
97			* denies access.
98	dl	1.17	*/
99			void shutdown();
100
101			/**
102			* Attempts to stop all actively executing tasks, halts the
103			* processing of waiting tasks, and returns a list of the tasks that were
104	jsr166	1.33	* awaiting execution.
105			*
106	dl	1.17	* <p>There are no guarantees beyond best-effort attempts to stop
107			* processing actively executing tasks. For example, typical
108	jsr166	1.39	* implementations will cancel via {@link Thread#interrupt}, so any
109			* task that fails to respond to interrupts may never terminate.
110	dl	1.17	*
111			* @return list of tasks that never commenced execution
112			* @throws SecurityException if a security manager exists and
113	jsr166	1.37	* shutting down this ExecutorService may manipulate
114			* threads that the caller is not permitted to modify
115			* because it does not hold {@link
116			* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
117			* or the security manager's <tt>checkAccess</tt> method
118			* denies access.
119	dl	1.17	*/
120			List<Runnable> shutdownNow();
121
122			/**
123			* Returns <tt>true</tt> if this executor has been shut down.
124			*
125			* @return <tt>true</tt> if this executor has been shut down
126			*/
127			boolean isShutdown();
128
129			/**
130			* Returns <tt>true</tt> if all tasks have completed following shut down.
131			* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
132			* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
133			*
134			* @return <tt>true</tt> if all tasks have completed following shut down
135			*/
136			boolean isTerminated();
137
138			/**
139			* Blocks until all tasks have completed execution after a shutdown
140			* request, or the timeout occurs, or the current thread is
141	jsr166	1.36	* interrupted, whichever happens first.
142	dl	1.17	*
143			* @param timeout the maximum time to wait
144			* @param unit the time unit of the timeout argument
145	jsr166	1.37	* @return <tt>true</tt> if this executor terminated and
146			* <tt>false</tt> if the timeout elapsed before termination
147	dl	1.17	* @throws InterruptedException if interrupted while waiting
148			*/
149			boolean awaitTermination(long timeout, TimeUnit unit)
150			throws InterruptedException;
151
152
153	tim	1.8	/**
154	dl	1.30	* Submits a value-returning task for execution and returns a
155	dl	1.31	* Future representing the pending results of the task. The
156	dl	1.32	* Future's <tt>get</tt> method will return the task's result upon
157	jsr166	1.37	* successful completion.
158	tim	1.8	*
159	dl	1.19	* <p>
160	dl	1.20	* If you would like to immediately block waiting
161	dl	1.19	* for a task, you can use constructions of the form
162			* <tt>result = exec.submit(aCallable).get();</tt>
163	dl	1.20	*
164			* <p> Note: The {@link Executors} class includes a set of methods
165			* that can convert some other common closure-like objects,
166			* for example, {@link java.security.PrivilegedAction} to
167			* {@link Callable} form so they can be submitted.
168			*
169	tim	1.8	* @param task the task to submit
170			* @return a Future representing pending completion of the task
171	jsr166	1.37	* @throws RejectedExecutionException if the task cannot be
172			* scheduled for execution
173			* @throws NullPointerException if the task is null
174	tim	1.8	*/
175			<T> Future<T> submit(Callable<T> task);
176
177			/**
178	dl	1.30	* Submits a Runnable task for execution and returns a Future
179	jsr166	1.33	* representing that task. The Future's <tt>get</tt> method will
180	dl	1.31	* return the given result upon successful completion.
181	dl	1.20	*
182			* @param task the task to submit
183			* @param result the result to return
184	dl	1.31	* @return a Future representing pending completion of the task
185	jsr166	1.37	* @throws RejectedExecutionException if the task cannot be
186			* scheduled for execution
187			* @throws NullPointerException if the task is null
188	dl	1.20	*/
189			<T> Future<T> submit(Runnable task, T result);
190
191			/**
192	jsr166	1.33	* Submits a Runnable task for execution and returns a Future
193			* representing that task. The Future's <tt>get</tt> method will
194	jsr166	1.37	* return <tt>null</tt> upon <em>successful</em> completion.
195	dl	1.1	*
196	dl	1.17	* @param task the task to submit
197	dl	1.31	* @return a Future representing pending completion of the task
198	jsr166	1.37	* @throws RejectedExecutionException if the task cannot be
199			* scheduled for execution
200			* @throws NullPointerException if the task is null
201	dl	1.1	*/
202	dl	1.18	Future<?> submit(Runnable task);
203	dl	1.15
204	dl	1.11	/**
205	dl	1.27	* Executes the given tasks, returning a list of Futures holding
206	jsr166	1.33	* their status and results when all complete.
207			* {@link Future#isDone} is <tt>true</tt> for each
208	dl	1.27	* element of the returned list.
209	dl	1.12	* Note that a <em>completed</em> task could have
210			* terminated either normally or by throwing an exception.
211	dl	1.21	* The results of this method are undefined if the given
212			* collection is modified while this operation is in progress.
213	jsr166	1.37	*
214	dl	1.11	* @param tasks the collection of tasks
215	dl	1.13	* @return A list of Futures representing the tasks, in the same
216	jsr166	1.37	* sequential order as produced by the iterator for the
217			* given task list, each of which has completed.
218	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
219	jsr166	1.37	* which case unfinished tasks are cancelled.
220	dl	1.13	* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
221	jsr166	1.37	* @throws RejectedExecutionException if any task cannot be
222			* scheduled for execution
223	dl	1.11	*/
224	jsr166	1.38
225			<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
226	dl	1.11	throws InterruptedException;
227
228			/**
229	dl	1.27	* Executes the given tasks, returning a list of Futures holding
230	jsr166	1.33	* their status and results
231	dl	1.15	* when all complete or the timeout expires, whichever happens first.
232	jsr166	1.33	* {@link Future#isDone} is <tt>true</tt> for each
233	dl	1.27	* element of the returned list.
234	dl	1.11	* Upon return, tasks that have not completed are cancelled.
235	dl	1.12	* Note that a <em>completed</em> task could have
236			* terminated either normally or by throwing an exception.
237	dl	1.21	* The results of this method are undefined if the given
238			* collection is modified while this operation is in progress.
239	jsr166	1.37	*
240	dl	1.11	* @param tasks the collection of tasks
241			* @param timeout the maximum time to wait
242	dl	1.15	* @param unit the time unit of the timeout argument
243	jsr166	1.37	* @return a list of Futures representing the tasks, in the same
244			* sequential order as produced by the iterator for the
245			* given task list. If the operation did not time out,
246			* each task will have completed. If it did time out, some
247			* of these tasks will not have completed.
248	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
249	jsr166	1.37	* which case unfinished tasks are cancelled
250	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
251	jsr166	1.37	* unit are <tt>null</tt>
252	dl	1.13	* @throws RejectedExecutionException if any task cannot be scheduled
253	jsr166	1.37	* for execution
254	dl	1.11	*/
255	jsr166	1.38	<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
256	jsr166	1.33	long timeout, TimeUnit unit)
257	dl	1.11	throws InterruptedException;
258
259			/**
260	dl	1.17	* Executes the given tasks, returning the result
261	dl	1.15	* of one that has completed successfully (i.e., without throwing
262			* an exception), if any do. Upon normal or exceptional return,
263			* tasks that have not completed are cancelled.
264	dl	1.21	* The results of this method are undefined if the given
265			* collection is modified while this operation is in progress.
266	jsr166	1.37	*
267	dl	1.11	* @param tasks the collection of tasks
268	jsr166	1.37	* @return the result returned by one of the tasks
269	dl	1.15	* @throws InterruptedException if interrupted while waiting
270			* @throws NullPointerException if tasks or any of its elements
271	jsr166	1.37	* are <tt>null</tt>
272			* @throws IllegalArgumentException if tasks is empty
273	dl	1.15	* @throws ExecutionException if no task successfully completes
274			* @throws RejectedExecutionException if tasks cannot be scheduled
275	jsr166	1.37	* for execution
276	dl	1.11	*/
277	jsr166	1.38	<T> T invokeAny(Collection<? extends Callable<T>> tasks)
278	dl	1.15	throws InterruptedException, ExecutionException;
279	dl	1.11
280			/**
281	dl	1.17	* Executes the given tasks, returning the result
282	dl	1.15	* of one that has completed successfully (i.e., without throwing
283			* an exception), if any do before the given timeout elapses.
284			* Upon normal or exceptional return, tasks that have not
285			* completed are cancelled.
286	dl	1.21	* The results of this method are undefined if the given
287			* collection is modified while this operation is in progress.
288	jsr166	1.37	*
289	dl	1.11	* @param tasks the collection of tasks
290			* @param timeout the maximum time to wait
291			* @param unit the time unit of the timeout argument
292	jsr166	1.37	* @return the result returned by one of the tasks.
293	dl	1.15	* @throws InterruptedException if interrupted while waiting
294	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
295	jsr166	1.37	* unit are <tt>null</tt>
296	dl	1.15	* @throws TimeoutException if the given timeout elapses before
297	jsr166	1.37	* any task successfully completes
298	dl	1.15	* @throws ExecutionException if no task successfully completes
299			* @throws RejectedExecutionException if tasks cannot be scheduled
300	jsr166	1.37	* for execution
301	dl	1.11	*/
302	jsr166	1.38	<T> T invokeAny(Collection<? extends Callable<T>> tasks,
303	jsr166	1.33	long timeout, TimeUnit unit)
304	dl	1.15	throws InterruptedException, ExecutionException, TimeoutException;
305	dl	1.1	}