util/concurrent/ExecutorService.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

package java.util.concurrent;

import java.util.List;
import java.util.Collection;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;

/**
 * An <tt>Executor</tt> 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 <tt>execute</tt> 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 customizable
 * versions of such methods.)
 *
 * <p>The {@link Executors} class provides factory methods for the
 * executor services provided in this package.
 *
 * @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.
     *
     * @param task the task to submit
     * @return a Future representing pending completion of the task
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     */
    <T> Future<T> submit(Callable<T> task);

    /**
     * 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
     */
    Future<?> submit(Runnable task);

    /**
     * Executes a value-returning task and blocks until it returns a
     * value or throws an exception.
     *
     * @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 InterruptedException if interrupted while waiting for
     * completion
     * @throws ExecutionException if the task encountered an exception
     * while executing
     */
    <T> T invoke(Callable<T> task) throws ExecutionException, InterruptedException;

    /**
     * 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.
     * @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.
     * @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.
     * @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.
     * @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:	1.18
Committed:	Fri Dec 19 20:38:31 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.17:	+14 -148 lines
Log Message:	Define and use Executors.callable instead of submit/invoke variants
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain. Use, modify, and
4			* redistribute this code in any way without acknowledgement.
5			*/
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	1.10	* An <tt>Executor</tt> that provides methods to manage termination
16	dl	1.17	* and methods that can produce a {@link Future} for tracking
17	dl	1.11	* progress of one or more asynchronous tasks.
18	dl	1.17	* <p>
19			*
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	1.18	* <p> Method <tt>submit</tt> extends base method <tt>execute</tt> by
27			* creating and returning a {@link Future} that can be used to cancel
28			* execution and/or wait for completion. Methods <tt>invokeAny</tt>
29			* and <tt>invokeAll</tt> perform the most commonly useful forms of
30			* bulk execution, executing a collection of tasks and then waiting
31			* for at least one, or all to complete. (Class {@link
32			* ExecutorCompletionService} can be used to write customizable
33	dl	1.17	* versions of such methods.)
34			*
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			* @since 1.5
39	dl	1.5	* @author Doug Lea
40	dl	1.1	*/
41			public interface ExecutorService extends Executor {
42	tim	1.8
43	dl	1.17
44			/**
45			* Initiates an orderly shutdown in which previously submitted
46			* tasks are executed, but no new tasks will be
47			* accepted. Invocation has no additional effect if already shut
48			* down.
49			* @throws SecurityException if a security manager exists and
50			* shutting down this ExecutorService may manipulate threads that
51			* the caller is not permitted to modify because it does not hold
52			* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
53			* or the security manager's <tt>checkAccess</tt> method denies access.
54			*/
55			void shutdown();
56
57			/**
58			* Attempts to stop all actively executing tasks, halts the
59			* processing of waiting tasks, and returns a list of the tasks that were
60			* awaiting execution.
61			*
62			* <p>There are no guarantees beyond best-effort attempts to stop
63			* processing actively executing tasks. For example, typical
64			* implementations will cancel via {@link Thread#interrupt}, so if any
65			* tasks mask or fail to respond to interrupts, they may never terminate.
66			*
67			* @return list of tasks that never commenced execution
68			* @throws SecurityException if a security manager exists and
69			* shutting down this ExecutorService may manipulate threads that
70			* the caller is not permitted to modify because it does not hold
71			* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
72			* or the security manager's <tt>checkAccess</tt> method denies access.
73			*/
74			List<Runnable> shutdownNow();
75
76			/**
77			* Returns <tt>true</tt> if this executor has been shut down.
78			*
79			* @return <tt>true</tt> if this executor has been shut down
80			*/
81			boolean isShutdown();
82
83			/**
84			* Returns <tt>true</tt> if all tasks have completed following shut down.
85			* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
86			* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
87			*
88			* @return <tt>true</tt> if all tasks have completed following shut down
89			*/
90			boolean isTerminated();
91
92			/**
93			* Blocks until all tasks have completed execution after a shutdown
94			* request, or the timeout occurs, or the current thread is
95			* interrupted, whichever happens first.
96			*
97			* @param timeout the maximum time to wait
98			* @param unit the time unit of the timeout argument
99			* @return <tt>true</tt> if this executor terminated and <tt>false</tt>
100			* if the timeout elapsed before termination
101			* @throws InterruptedException if interrupted while waiting
102			*/
103			boolean awaitTermination(long timeout, TimeUnit unit)
104			throws InterruptedException;
105
106
107	tim	1.8	/**
108			* Submits a value-returning task for execution and returns a Future
109			* representing the pending results of the task.
110			*
111			* @param task the task to submit
112			* @return a Future representing pending completion of the task
113			* @throws RejectedExecutionException if task cannot be scheduled
114			* for execution
115			*/
116			<T> Future<T> submit(Callable<T> task);
117
118			/**
119	dl	1.18	* Submits a Runnable task for execution and returns a Future
120			* representing that task.
121	dl	1.1	*
122	dl	1.17	* @param task the task to submit
123	dl	1.18	* @return a Future representing pending completion of the task,
124			* and whose <tt>get()</tt> method will return <tt>null</tt>
125			* upon completion.
126	dl	1.17	* @throws RejectedExecutionException if task cannot be scheduled
127			* for execution
128	dl	1.1	*/
129	dl	1.18	Future<?> submit(Runnable task);
130	dl	1.1
131			/**
132	dl	1.17	* Executes a value-returning task and blocks until it returns a
133			* value or throws an exception.
134	dl	1.1	*
135	dl	1.17	* @param task the task to submit
136			* @return a Future representing pending completion of the task
137			* @throws RejectedExecutionException if task cannot be scheduled
138			* for execution
139			* @throws InterruptedException if interrupted while waiting for
140			* completion
141			* @throws ExecutionException if the task encountered an exception
142			* while executing
143	dl	1.1	*/
144	dl	1.17	<T> T invoke(Callable<T> task) throws ExecutionException, InterruptedException;
145	dl	1.15
146	dl	1.11	/**
147	dl	1.17	* Executes the given tasks, returning their results
148	dl	1.15	* when all complete.
149	dl	1.12	* Note that a <em>completed</em> task could have
150			* terminated either normally or by throwing an exception.
151	dl	1.11	* @param tasks the collection of tasks
152	dl	1.13	* @return A list of Futures representing the tasks, in the same
153	dl	1.16	* sequential order as produced by the iterator for the given task list, each of which has
154	dl	1.13	* completed.
155	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
156			* which case unfinished tasks are cancelled.
157	dl	1.13	* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
158			* @throws RejectedExecutionException if any task cannot be scheduled
159			* for execution
160	dl	1.11	*/
161	dl	1.15
162	dl	1.16	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
163	dl	1.11	throws InterruptedException;
164
165			/**
166	dl	1.17	* Executes the given tasks, returning their results
167	dl	1.15	* when all complete or the timeout expires, whichever happens first.
168	dl	1.11	* Upon return, tasks that have not completed are cancelled.
169	dl	1.12	* Note that a <em>completed</em> task could have
170			* terminated either normally or by throwing an exception.
171	dl	1.11	* @param tasks the collection of tasks
172			* @param timeout the maximum time to wait
173	dl	1.15	* @param unit the time unit of the timeout argument
174	dl	1.13	* @return A list of Futures representing the tasks, in the same
175	dl	1.16	* sequential order as as produced by the iterator for the given task list. If the operation did
176	dl	1.13	* not time out, each task will have completed. If it did time
177	dl	1.15	* out, some of thiese tasks will not have completed.
178	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
179			* which case unfinished tasks are cancelled.
180	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
181	dl	1.15	* unit are <tt>null</tt>
182	dl	1.13	* @throws RejectedExecutionException if any task cannot be scheduled
183			* for execution
184	dl	1.11	*/
185	dl	1.16	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
186	dl	1.18	long timeout, TimeUnit unit)
187	dl	1.11	throws InterruptedException;
188
189			/**
190	dl	1.17	* Executes the given tasks, returning the result
191	dl	1.15	* of one that has completed successfully (i.e., without throwing
192			* an exception), if any do. Upon normal or exceptional return,
193			* tasks that have not completed are cancelled.
194	dl	1.11	* @param tasks the collection of tasks
195	dl	1.15	* @return The result returned by one of the tasks.
196			* @throws InterruptedException if interrupted while waiting
197			* @throws NullPointerException if tasks or any of its elements
198			* are <tt>null</tt>
199			* @throws IllegalArgumentException if tasks empty
200			* @throws ExecutionException if no task successfully completes
201			* @throws RejectedExecutionException if tasks cannot be scheduled
202	dl	1.13	* for execution
203	dl	1.11	*/
204	dl	1.15	<T> T invokeAny(Collection<Callable<T>> tasks)
205			throws InterruptedException, ExecutionException;
206	dl	1.11
207			/**
208	dl	1.17	* Executes the given tasks, returning the result
209	dl	1.15	* of one that has completed successfully (i.e., without throwing
210			* an exception), if any do before the given timeout elapses.
211			* Upon normal or exceptional return, tasks that have not
212			* completed are cancelled.
213	dl	1.11	* @param tasks the collection of tasks
214			* @param timeout the maximum time to wait
215			* @param unit the time unit of the timeout argument
216	dl	1.15	* @return The result returned by one of the tasks.
217			* @throws InterruptedException if interrupted while waiting
218	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
219	dl	1.15	* unit are <tt>null</tt>
220			* @throws TimeoutException if the given timeout elapses before
221			* any task successfully completes
222			* @throws ExecutionException if no task successfully completes
223			* @throws RejectedExecutionException if tasks cannot be scheduled
224	dl	1.13	* for execution
225	dl	1.11	*/
226	dl	1.15	<T> T invokeAny(Collection<Callable<T>> tasks,
227			long timeout, TimeUnit unit)
228			throws InterruptedException, ExecutionException, TimeoutException;
229	dl	1.3
230	dl	1.1	}