util/concurrent/ExecutorService.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

package java.util.concurrent;
import java.util.concurrent.*; // for javadoc (till 6280605 is fixed)
import java.util.List;
import java.util.Collection;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;

/**
 * An {@link Executor} that provides methods to manage termination and
 * methods that can produce a {@link Future} for tracking progress of
 * one or more asynchronous tasks.
 *
 * <p>
 * An <tt>ExecutorService</tt> can be shut down, which will cause it
 * to stop accepting new tasks.  After being shut down, the executor
 * will eventually terminate, at which point no tasks are actively
 * executing, no tasks are awaiting execution, and no new tasks can be
 * submitted.
 *
 * <p> Method <tt>submit</tt> extends base method {@link
 * Executor#execute} by creating and returning a {@link Future} that
 * can be used to cancel execution and/or wait for completion.
 * Methods <tt>invokeAny</tt> and <tt>invokeAll</tt> perform the most
 * commonly useful forms of bulk execution, executing a collection of
 * tasks and then waiting for at least one, or all, to
 * complete. (Class {@link ExecutorCompletionService} can be used to
 * write customized variants of these methods.)
 *
 * <p>The {@link Executors} class provides factory methods for the
 * executor services provided in this package.
 *
 * <h3>Usage Example</h3>
 *
 * Here is a sketch of a network service in which threads in a thread
 * pool service incoming requests. It uses the preconfigured {@link
 * Executors#newFixedThreadPool} factory method:
 *
 * <pre>
 * class NetworkService {
 *   private final ServerSocket serverSocket;
 *   private final ExecutorService pool;
 *
 *   public NetworkService(int port, int poolSize)
 *       throws IOException {
 *     serverSocket = new ServerSocket(port);
 *     pool = Executors.newFixedThreadPool(poolSize);
 *   }
 *
 *   public void serve() {
 *     try {
 *       for (;;) {
 *         pool.execute(new Handler(serverSocket.accept()));
 *       }
 *     } catch (IOException ex) {
 *       pool.shutdown();
 *     }
 *   }
 * }
 *
 * class Handler implements Runnable {
 *   private final Socket socket;
 *   Handler(Socket socket) { this.socket = socket; }
 *   public void run() {
 *     // read and service request
 *   }
 * }
 * </pre>
 *
 * Memory visibility effects: State changes to a <tt>Runnable</tt> or
 * <tt>Callable</tt> object made prior to submission to an
 * <tt>Executor</tt> <a
 * href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
 * its execution, and state changes to objects returned from a
 * <tt>Callable</tt> * <i>happen-before</i> that object is returned to
 * a thread which calls <tt>Future.get()</tt> to retrieve that result.
 *
 * @since 1.5
 * @author Doug Lea
 */
public interface ExecutorService extends Executor {

    /**
     * Initiates an orderly shutdown in which previously submitted
     * tasks are executed, but no new tasks will be accepted.
     * Invocation has no additional effect if already shut down.
     *
     * @throws SecurityException if a security manager exists and
     *         shutting down this ExecutorService may manipulate
     *         threads that the caller is not permitted to modify
     *         because it does not hold {@link
     *         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
     *         or the security manager's <tt>checkAccess</tt> method
     *         denies access.
     */
    void shutdown();

    /**
     * Attempts to stop all actively executing tasks, halts the
     * processing of waiting tasks, and returns a list of the tasks that were
     * awaiting execution.
     *
     * <p>There are no guarantees beyond best-effort attempts to stop
     * processing actively executing tasks.  For example, typical
     * implementations will cancel via {@link Thread#interrupt}, so any
     * task that fails to respond to interrupts may never terminate.
     *
     * @return list of tasks that never commenced execution
     * @throws SecurityException if a security manager exists and
     *         shutting down this ExecutorService may manipulate
     *         threads that the caller is not permitted to modify
     *         because it does not hold {@link
     *         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
     *         or the security manager's <tt>checkAccess</tt> method
     *         denies access.
     */
    List<Runnable> shutdownNow();

    /**
     * Returns <tt>true</tt> if this executor has been shut down.
     *
     * @return <tt>true</tt> if this executor has been shut down
     */
    boolean isShutdown();

    /**
     * Returns <tt>true</tt> if all tasks have completed following shut down.
     * Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
     * either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
     *
     * @return <tt>true</tt> if all tasks have completed following shut down
     */
    boolean isTerminated();

    /**
     * Blocks until all tasks have completed execution after a shutdown
     * request, or the timeout occurs, or the current thread is
     * interrupted, whichever happens first.
     *
     * @param timeout the maximum time to wait
     * @param unit the time unit of the timeout argument
     * @return <tt>true</tt> if this executor terminated and
     *         <tt>false</tt> if the timeout elapsed before termination
     * @throws InterruptedException if interrupted while waiting
     */
    boolean awaitTermination(long timeout, TimeUnit unit)
        throws InterruptedException;


    /**
     * Submits a value-returning task for execution and returns a
     * Future representing the pending results of the task. The
     * Future's <tt>get</tt> method will return the task's result upon
     * successful completion.
     *
     * <p>
     * If you would like to immediately block waiting
     * for a task, you can use constructions of the form
     * <tt>result = exec.submit(aCallable).get();</tt>
     *
     * <p> Note: The {@link Executors} class includes a set of methods
     * that can convert some other common closure-like objects,
     * for example, {@link java.security.PrivilegedAction} to
     * {@link Callable} form so they can be submitted.
     *
     * @param task the task to submit
     * @return a Future representing pending completion of the task
     * @throws RejectedExecutionException if the task cannot be
     *         scheduled for execution
     * @throws NullPointerException if the task is null
     */
    <T> Future<T> submit(Callable<T> task);

    /**
     * Submits a Runnable task for execution and returns a Future
     * representing that task. The Future's <tt>get</tt> method will
     * return the given result upon successful completion.
     *
     * @param task the task to submit
     * @param result the result to return
     * @return a Future representing pending completion of the task
     * @throws RejectedExecutionException if the task cannot be
     *         scheduled for execution
     * @throws NullPointerException if the task is null
     */
    <T> Future<T> submit(Runnable task, T result);

    /**
     * Submits a Runnable task for execution and returns a Future
     * representing that task. The Future's <tt>get</tt> method will
     * return <tt>null</tt> upon <em>successful</em> completion.
     *
     * @param task the task to submit
     * @return a Future representing pending completion of the task
     * @throws RejectedExecutionException if the task cannot be
     *         scheduled for execution
     * @throws NullPointerException if the task is null
     */
    Future<?> submit(Runnable task);

    /**
     * Executes the given tasks, returning a list of Futures holding
     * their status and results when all complete.
     * {@link Future#isDone} is <tt>true</tt> for each
     * element of the returned list.
     * Note that a <em>completed</em> task could have
     * terminated either normally or by throwing an exception.
     * The results of this method are undefined if the given
     * collection is modified while this operation is in progress.
     *
     * @param tasks the collection of tasks
     * @return A list of Futures representing the tasks, in the same
     *         sequential order as produced by the iterator for the
     *         given task list, each of which has completed.
     * @throws InterruptedException if interrupted while waiting, in
     *         which case unfinished tasks are cancelled.
     * @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
     * @throws RejectedExecutionException if any task cannot be
     *         scheduled for execution
     */

    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
        throws InterruptedException;

    /**
     * Executes the given tasks, returning a list of Futures holding
     * their status and results
     * when all complete or the timeout expires, whichever happens first.
     * {@link Future#isDone} is <tt>true</tt> for each
     * element of the returned list.
     * Upon return, tasks that have not completed are cancelled.
     * Note that a <em>completed</em> task could have
     * terminated either normally or by throwing an exception.
     * The results of this method are undefined if the given
     * collection is modified while this operation is in progress.
     *
     * @param tasks the collection of tasks
     * @param timeout the maximum time to wait
     * @param unit the time unit of the timeout argument
     * @return a list of Futures representing the tasks, in the same
     *         sequential order as produced by the iterator for the
     *         given task list. If the operation did not time out,
     *         each task will have completed. If it did time out, some
     *         of these tasks will not have completed.
     * @throws InterruptedException if interrupted while waiting, in
     *         which case unfinished tasks are cancelled
     * @throws NullPointerException if tasks, any of its elements, or
     *         unit are <tt>null</tt>
     * @throws RejectedExecutionException if any task cannot be scheduled
     *         for execution
     */
    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
                                  long timeout, TimeUnit unit)
        throws InterruptedException;

    /**
     * Executes the given tasks, returning the result
     * of one that has completed successfully (i.e., without throwing
     * an exception), if any do. Upon normal or exceptional return,
     * tasks that have not completed are cancelled.
     * The results of this method are undefined if the given
     * collection is modified while this operation is in progress.
     *
     * @param tasks the collection of tasks
     * @return the result returned by one of the tasks
     * @throws InterruptedException if interrupted while waiting
     * @throws NullPointerException if tasks or any of its elements
     *         are <tt>null</tt>
     * @throws IllegalArgumentException if tasks is empty
     * @throws ExecutionException if no task successfully completes
     * @throws RejectedExecutionException if tasks cannot be scheduled
     *         for execution
     */
    <T> T invokeAny(Collection<? extends Callable<T>> tasks)
        throws InterruptedException, ExecutionException;

    /**
     * Executes the given tasks, returning the result
     * of one that has completed successfully (i.e., without throwing
     * an exception), if any do before the given timeout elapses.
     * Upon normal or exceptional return, tasks that have not
     * completed are cancelled.
     * The results of this method are undefined if the given
     * collection is modified while this operation is in progress.
     *
     * @param tasks the collection of tasks
     * @param timeout the maximum time to wait
     * @param unit the time unit of the timeout argument
     * @return the result returned by one of the tasks.
     * @throws InterruptedException if interrupted while waiting
     * @throws NullPointerException if tasks, any of its elements, or
     *         unit are <tt>null</tt>
     * @throws TimeoutException if the given timeout elapses before
     *         any task successfully completes
     * @throws ExecutionException if no task successfully completes
     * @throws RejectedExecutionException if tasks cannot be scheduled
     *         for execution
     */
    <T> T invokeAny(Collection<? extends Callable<T>> tasks,
                    long timeout, TimeUnit unit)
        throws InterruptedException, ExecutionException, TimeoutException;
}
Revision:	1.40
Committed:	Fri Sep 2 01:03:08 2005 UTC (18 years, 9 months ago) by brian
Branch:	MAIN
Changes since 1.39:	+9 -0 lines
Log Message:	Happens-before markup
#	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	jsr166	1.37	import java.util.concurrent.*; // for javadoc (till 6280605 is fixed)
9	dl	1.1	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	jsr166	1.33	* 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	jsr166	1.37	* private final ServerSocket serverSocket;
47			* private final ExecutorService pool;
48	dl	1.23	*
49	jsr166	1.37	* public NetworkService(int port, int poolSize)
50			* throws IOException {
51			* serverSocket = new ServerSocket(port);
52			* pool = Executors.newFixedThreadPool(poolSize);
53			* }
54	jsr166	1.33	*
55	jsr166	1.37	* public void serve() {
56			* try {
57			* for (;;) {
58			* pool.execute(new Handler(serverSocket.accept()));
59			* }
60			* } catch (IOException ex) {
61			* pool.shutdown();
62			* }
63			* }
64			* }
65	dl	1.23	*
66	jsr166	1.37	* class Handler implements Runnable {
67			* private final Socket socket;
68			* Handler(Socket socket) { this.socket = socket; }
69			* public void run() {
70			* // read and service request
71			* }
72	dl	1.23	* }
73			* </pre>
74	brian	1.40	*
75			* Memory visibility effects: State changes to a <tt>Runnable</tt> or
76			* <tt>Callable</tt> object made prior to submission to an
77			* <tt>Executor</tt> <a
78			* href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
79			* its execution, and state changes to objects returned from a
80			* <tt>Callable</tt> * <i>happen-before</i> that object is returned to
81			* a thread which calls <tt>Future.get()</tt> to retrieve that result.
82			*
83	dl	1.1	* @since 1.5
84	dl	1.5	* @author Doug Lea
85	dl	1.1	*/
86			public interface ExecutorService extends Executor {
87	tim	1.8
88	dl	1.17	/**
89			* Initiates an orderly shutdown in which previously submitted
90	jsr166	1.37	* tasks are executed, but no new tasks will be accepted.
91			* Invocation has no additional effect if already shut down.
92			*
93	dl	1.17	* @throws SecurityException if a security manager exists and
94	jsr166	1.37	* shutting down this ExecutorService may manipulate
95			* threads that the caller is not permitted to modify
96			* because it does not hold {@link
97			* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
98			* or the security manager's <tt>checkAccess</tt> method
99			* denies access.
100	dl	1.17	*/
101			void shutdown();
102
103			/**
104			* Attempts to stop all actively executing tasks, halts the
105			* processing of waiting tasks, and returns a list of the tasks that were
106	jsr166	1.33	* awaiting execution.
107			*
108	dl	1.17	* <p>There are no guarantees beyond best-effort attempts to stop
109			* processing actively executing tasks. For example, typical
110	jsr166	1.39	* implementations will cancel via {@link Thread#interrupt}, so any
111			* task that fails to respond to interrupts may never terminate.
112	dl	1.17	*
113			* @return list of tasks that never commenced execution
114			* @throws SecurityException if a security manager exists and
115	jsr166	1.37	* shutting down this ExecutorService may manipulate
116			* threads that the caller is not permitted to modify
117			* because it does not hold {@link
118			* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
119			* or the security manager's <tt>checkAccess</tt> method
120			* denies access.
121	dl	1.17	*/
122			List<Runnable> shutdownNow();
123
124			/**
125			* Returns <tt>true</tt> if this executor has been shut down.
126			*
127			* @return <tt>true</tt> if this executor has been shut down
128			*/
129			boolean isShutdown();
130
131			/**
132			* Returns <tt>true</tt> if all tasks have completed following shut down.
133			* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
134			* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
135			*
136			* @return <tt>true</tt> if all tasks have completed following shut down
137			*/
138			boolean isTerminated();
139
140			/**
141			* Blocks until all tasks have completed execution after a shutdown
142			* request, or the timeout occurs, or the current thread is
143	jsr166	1.36	* interrupted, whichever happens first.
144	dl	1.17	*
145			* @param timeout the maximum time to wait
146			* @param unit the time unit of the timeout argument
147	jsr166	1.37	* @return <tt>true</tt> if this executor terminated and
148			* <tt>false</tt> if the timeout elapsed before termination
149	dl	1.17	* @throws InterruptedException if interrupted while waiting
150			*/
151			boolean awaitTermination(long timeout, TimeUnit unit)
152			throws InterruptedException;
153
154
155	tim	1.8	/**
156	dl	1.30	* Submits a value-returning task for execution and returns a
157	dl	1.31	* Future representing the pending results of the task. The
158	dl	1.32	* Future's <tt>get</tt> method will return the task's result upon
159	jsr166	1.37	* successful completion.
160	tim	1.8	*
161	dl	1.19	* <p>
162	dl	1.20	* If you would like to immediately block waiting
163	dl	1.19	* for a task, you can use constructions of the form
164			* <tt>result = exec.submit(aCallable).get();</tt>
165	dl	1.20	*
166			* <p> Note: The {@link Executors} class includes a set of methods
167			* that can convert some other common closure-like objects,
168			* for example, {@link java.security.PrivilegedAction} to
169			* {@link Callable} form so they can be submitted.
170			*
171	tim	1.8	* @param task the task to submit
172			* @return a Future representing pending completion of the task
173	jsr166	1.37	* @throws RejectedExecutionException if the task cannot be
174			* scheduled for execution
175			* @throws NullPointerException if the task is null
176	tim	1.8	*/
177			<T> Future<T> submit(Callable<T> task);
178
179			/**
180	dl	1.30	* Submits a Runnable task for execution and returns a Future
181	jsr166	1.33	* representing that task. The Future's <tt>get</tt> method will
182	dl	1.31	* return the given result upon successful completion.
183	dl	1.20	*
184			* @param task the task to submit
185			* @param result the result to return
186	dl	1.31	* @return a Future representing pending completion of the task
187	jsr166	1.37	* @throws RejectedExecutionException if the task cannot be
188			* scheduled for execution
189			* @throws NullPointerException if the task is null
190	dl	1.20	*/
191			<T> Future<T> submit(Runnable task, T result);
192
193			/**
194	jsr166	1.33	* Submits a Runnable task for execution and returns a Future
195			* representing that task. The Future's <tt>get</tt> method will
196	jsr166	1.37	* return <tt>null</tt> upon <em>successful</em> completion.
197	dl	1.1	*
198	dl	1.17	* @param task the task to submit
199	dl	1.31	* @return a Future representing pending completion of the task
200	jsr166	1.37	* @throws RejectedExecutionException if the task cannot be
201			* scheduled for execution
202			* @throws NullPointerException if the task is null
203	dl	1.1	*/
204	dl	1.18	Future<?> submit(Runnable task);
205	dl	1.15
206	dl	1.11	/**
207	dl	1.27	* Executes the given tasks, returning a list of Futures holding
208	jsr166	1.33	* their status and results when all complete.
209			* {@link Future#isDone} is <tt>true</tt> for each
210	dl	1.27	* element of the returned list.
211	dl	1.12	* Note that a <em>completed</em> task could have
212			* terminated either normally or by throwing an exception.
213	dl	1.21	* The results of this method are undefined if the given
214			* collection is modified while this operation is in progress.
215	jsr166	1.37	*
216	dl	1.11	* @param tasks the collection of tasks
217	dl	1.13	* @return A list of Futures representing the tasks, in the same
218	jsr166	1.37	* sequential order as produced by the iterator for the
219			* given task list, each of which has completed.
220	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
221	jsr166	1.37	* which case unfinished tasks are cancelled.
222	dl	1.13	* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
223	jsr166	1.37	* @throws RejectedExecutionException if any task cannot be
224			* scheduled for execution
225	dl	1.11	*/
226	jsr166	1.38
227			<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
228	dl	1.11	throws InterruptedException;
229
230			/**
231	dl	1.27	* Executes the given tasks, returning a list of Futures holding
232	jsr166	1.33	* their status and results
233	dl	1.15	* when all complete or the timeout expires, whichever happens first.
234	jsr166	1.33	* {@link Future#isDone} is <tt>true</tt> for each
235	dl	1.27	* element of the returned list.
236	dl	1.11	* Upon return, tasks that have not completed are cancelled.
237	dl	1.12	* Note that a <em>completed</em> task could have
238			* terminated either normally or by throwing an exception.
239	dl	1.21	* The results of this method are undefined if the given
240			* collection is modified while this operation is in progress.
241	jsr166	1.37	*
242	dl	1.11	* @param tasks the collection of tasks
243			* @param timeout the maximum time to wait
244	dl	1.15	* @param unit the time unit of the timeout argument
245	jsr166	1.37	* @return a list of Futures representing the tasks, in the same
246			* sequential order as produced by the iterator for the
247			* given task list. If the operation did not time out,
248			* each task will have completed. If it did time out, some
249			* of these tasks will not have completed.
250	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
251	jsr166	1.37	* which case unfinished tasks are cancelled
252	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
253	jsr166	1.37	* unit are <tt>null</tt>
254	dl	1.13	* @throws RejectedExecutionException if any task cannot be scheduled
255	jsr166	1.37	* for execution
256	dl	1.11	*/
257	jsr166	1.38	<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
258	jsr166	1.33	long timeout, TimeUnit unit)
259	dl	1.11	throws InterruptedException;
260
261			/**
262	dl	1.17	* Executes the given tasks, returning the result
263	dl	1.15	* of one that has completed successfully (i.e., without throwing
264			* an exception), if any do. Upon normal or exceptional return,
265			* tasks that have not completed are cancelled.
266	dl	1.21	* The results of this method are undefined if the given
267			* collection is modified while this operation is in progress.
268	jsr166	1.37	*
269	dl	1.11	* @param tasks the collection of tasks
270	jsr166	1.37	* @return the result returned by one of the tasks
271	dl	1.15	* @throws InterruptedException if interrupted while waiting
272			* @throws NullPointerException if tasks or any of its elements
273	jsr166	1.37	* are <tt>null</tt>
274			* @throws IllegalArgumentException if tasks is empty
275	dl	1.15	* @throws ExecutionException if no task successfully completes
276			* @throws RejectedExecutionException if tasks cannot be scheduled
277	jsr166	1.37	* for execution
278	dl	1.11	*/
279	jsr166	1.38	<T> T invokeAny(Collection<? extends Callable<T>> tasks)
280	dl	1.15	throws InterruptedException, ExecutionException;
281	dl	1.11
282			/**
283	dl	1.17	* Executes the given tasks, returning the result
284	dl	1.15	* of one that has completed successfully (i.e., without throwing
285			* an exception), if any do before the given timeout elapses.
286			* Upon normal or exceptional return, tasks that have not
287			* completed are cancelled.
288	dl	1.21	* The results of this method are undefined if the given
289			* collection is modified while this operation is in progress.
290	jsr166	1.37	*
291	dl	1.11	* @param tasks the collection of tasks
292			* @param timeout the maximum time to wait
293			* @param unit the time unit of the timeout argument
294	jsr166	1.37	* @return the result returned by one of the tasks.
295	dl	1.15	* @throws InterruptedException if interrupted while waiting
296	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
297	jsr166	1.37	* unit are <tt>null</tt>
298	dl	1.15	* @throws TimeoutException if the given timeout elapses before
299	jsr166	1.37	* any task successfully completes
300	dl	1.15	* @throws ExecutionException if no task successfully completes
301			* @throws RejectedExecutionException if tasks cannot be scheduled
302	jsr166	1.37	* for execution
303	dl	1.11	*/
304	jsr166	1.38	<T> T invokeAny(Collection<? extends Callable<T>> tasks,
305	jsr166	1.33	long timeout, TimeUnit unit)
306	dl	1.15	throws InterruptedException, ExecutionException, TimeoutException;
307	dl	1.1	}