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 {@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.
 *
 * @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:	1.21
Committed:	Mon Dec 22 16:25:20 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.20:	+14 -5 lines
Log Message:	Simplify FutureTask and AbstractExecutorService internals; improve docs
#	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	1.20	* An {@link Executor} that provides methods to manage termination and
16			* 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			* @since 1.5
38	dl	1.5	* @author Doug Lea
39	dl	1.1	*/
40			public interface ExecutorService extends Executor {
41	tim	1.8
42	dl	1.17	/**
43			* Initiates an orderly shutdown in which previously submitted
44			* tasks are executed, but no new tasks will be
45			* accepted. Invocation has no additional effect if already shut
46			* down.
47			* @throws SecurityException if a security manager exists and
48			* shutting down this ExecutorService may manipulate threads that
49			* the caller is not permitted to modify because it does not hold
50			* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
51			* or the security manager's <tt>checkAccess</tt> method denies access.
52			*/
53			void shutdown();
54
55			/**
56			* Attempts to stop all actively executing tasks, halts the
57			* processing of waiting tasks, and returns a list of the tasks that were
58			* awaiting execution.
59			*
60			* <p>There are no guarantees beyond best-effort attempts to stop
61			* processing actively executing tasks. For example, typical
62			* implementations will cancel via {@link Thread#interrupt}, so if any
63			* tasks mask or fail to respond to interrupts, they may never terminate.
64			*
65			* @return list of tasks that never commenced execution
66			* @throws SecurityException if a security manager exists and
67			* shutting down this ExecutorService may manipulate threads that
68			* the caller is not permitted to modify because it does not hold
69			* {@link java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
70			* or the security manager's <tt>checkAccess</tt> method denies access.
71			*/
72			List<Runnable> shutdownNow();
73
74			/**
75			* Returns <tt>true</tt> if this executor has been shut down.
76			*
77			* @return <tt>true</tt> if this executor has been shut down
78			*/
79			boolean isShutdown();
80
81			/**
82			* Returns <tt>true</tt> if all tasks have completed following shut down.
83			* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
84			* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
85			*
86			* @return <tt>true</tt> if all tasks have completed following shut down
87			*/
88			boolean isTerminated();
89
90			/**
91			* Blocks until all tasks have completed execution after a shutdown
92			* request, or the timeout occurs, or the current thread is
93			* interrupted, whichever happens first.
94			*
95			* @param timeout the maximum time to wait
96			* @param unit the time unit of the timeout argument
97			* @return <tt>true</tt> if this executor terminated and <tt>false</tt>
98			* if the timeout elapsed before termination
99			* @throws InterruptedException if interrupted while waiting
100			*/
101			boolean awaitTermination(long timeout, TimeUnit unit)
102			throws InterruptedException;
103
104
105	tim	1.8	/**
106			* Submits a value-returning task for execution and returns a Future
107	dl	1.19	* representing the pending results of the task.
108	tim	1.8	*
109	dl	1.19	* <p>
110	dl	1.20	* If you would like to immediately block waiting
111	dl	1.19	* for a task, you can use constructions of the form
112			* <tt>result = exec.submit(aCallable).get();</tt>
113	dl	1.20	*
114			* <p> Note: The {@link Executors} class includes a set of methods
115			* that can convert some other common closure-like objects,
116			* for example, {@link java.security.PrivilegedAction} to
117			* {@link Callable} form so they can be submitted.
118			*
119	tim	1.8	* @param task the task to submit
120			* @return a Future representing pending completion of the task
121			* @throws RejectedExecutionException if task cannot be scheduled
122			* for execution
123	dl	1.20	* @throws NullPointerException if task null
124	tim	1.8	*/
125			<T> Future<T> submit(Callable<T> task);
126
127			/**
128	dl	1.18	* Submits a Runnable task for execution and returns a Future
129	dl	1.20	* representing that task that will upon completion return
130			* the given result
131			*
132			* @param task the task to submit
133			* @param result the result to return
134			* @return a Future representing pending completion of the task,
135			* and whose <tt>get()</tt> method will return the given result
136			* upon completion.
137			* @throws RejectedExecutionException if task cannot be scheduled
138			* for execution
139			* @throws NullPointerException if task null
140			*/
141			<T> Future<T> submit(Runnable task, T result);
142
143			/**
144			* Submits a Runnable task for execution and returns a Future
145	dl	1.18	* representing that task.
146	dl	1.1	*
147	dl	1.17	* @param task the task to submit
148	dl	1.18	* @return a Future representing pending completion of the task,
149			* and whose <tt>get()</tt> method will return <tt>null</tt>
150			* upon completion.
151	dl	1.17	* @throws RejectedExecutionException if task cannot be scheduled
152			* for execution
153	dl	1.20	* @throws NullPointerException if task null
154	dl	1.1	*/
155	dl	1.18	Future<?> submit(Runnable task);
156	dl	1.15
157	dl	1.11	/**
158	dl	1.17	* Executes the given tasks, returning their results
159	dl	1.15	* when all complete.
160	dl	1.12	* Note that a <em>completed</em> task could have
161			* terminated either normally or by throwing an exception.
162	dl	1.21	* The results of this method are undefined if the given
163			* collection is modified while this operation is in progress.
164	dl	1.11	* @param tasks the collection of tasks
165	dl	1.13	* @return A list of Futures representing the tasks, in the same
166	dl	1.21	* sequential order as produced by the iterator for the given task
167			* list, each of which has completed.
168	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
169			* which case unfinished tasks are cancelled.
170	dl	1.13	* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
171			* @throws RejectedExecutionException if any task cannot be scheduled
172			* for execution
173	dl	1.11	*/
174	dl	1.15
175	dl	1.16	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
176	dl	1.11	throws InterruptedException;
177
178			/**
179	dl	1.17	* Executes the given tasks, returning their results
180	dl	1.15	* when all complete or the timeout expires, whichever happens first.
181	dl	1.11	* Upon return, tasks that have not completed are cancelled.
182	dl	1.12	* Note that a <em>completed</em> task could have
183			* terminated either normally or by throwing an exception.
184	dl	1.21	* The results of this method are undefined if the given
185			* collection is modified while this operation is in progress.
186	dl	1.11	* @param tasks the collection of tasks
187			* @param timeout the maximum time to wait
188	dl	1.15	* @param unit the time unit of the timeout argument
189	dl	1.13	* @return A list of Futures representing the tasks, in the same
190	dl	1.21	* sequential order as as produced by the iterator for the given
191			* task list. If the operation did not time out, each task will
192			* have completed. If it did time out, some of thiese tasks will
193			* not have completed.
194	dl	1.11	* @throws InterruptedException if interrupted while waiting, in
195			* which case unfinished tasks are cancelled.
196	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
197	dl	1.15	* unit are <tt>null</tt>
198	dl	1.13	* @throws RejectedExecutionException if any task cannot be scheduled
199			* for execution
200	dl	1.11	*/
201	dl	1.16	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
202	dl	1.18	long timeout, TimeUnit unit)
203	dl	1.11	throws InterruptedException;
204
205			/**
206	dl	1.17	* Executes the given tasks, returning the result
207	dl	1.15	* of one that has completed successfully (i.e., without throwing
208			* an exception), if any do. Upon normal or exceptional return,
209			* tasks that have not completed are cancelled.
210	dl	1.21	* The results of this method are undefined if the given
211			* collection is modified while this operation is in progress.
212	dl	1.11	* @param tasks the collection of tasks
213	dl	1.15	* @return The result returned by one of the tasks.
214			* @throws InterruptedException if interrupted while waiting
215			* @throws NullPointerException if tasks or any of its elements
216			* are <tt>null</tt>
217			* @throws IllegalArgumentException if tasks empty
218			* @throws ExecutionException if no task successfully completes
219			* @throws RejectedExecutionException if tasks cannot be scheduled
220	dl	1.13	* for execution
221	dl	1.11	*/
222	dl	1.15	<T> T invokeAny(Collection<Callable<T>> tasks)
223			throws InterruptedException, ExecutionException;
224	dl	1.11
225			/**
226	dl	1.17	* Executes the given tasks, returning the result
227	dl	1.15	* of one that has completed successfully (i.e., without throwing
228			* an exception), if any do before the given timeout elapses.
229			* Upon normal or exceptional return, tasks that have not
230			* completed are cancelled.
231	dl	1.21	* The results of this method are undefined if the given
232			* collection is modified while this operation is in progress.
233	dl	1.11	* @param tasks the collection of tasks
234			* @param timeout the maximum time to wait
235			* @param unit the time unit of the timeout argument
236	dl	1.15	* @return The result returned by one of the tasks.
237			* @throws InterruptedException if interrupted while waiting
238	dl	1.17	* @throws NullPointerException if tasks, any of its elements, or
239	dl	1.15	* unit are <tt>null</tt>
240			* @throws TimeoutException if the given timeout elapses before
241			* any task successfully completes
242			* @throws ExecutionException if no task successfully completes
243			* @throws RejectedExecutionException if tasks cannot be scheduled
244	dl	1.13	* for execution
245	dl	1.11	*/
246	dl	1.15	<T> T invokeAny(Collection<Callable<T>> tasks,
247			long timeout, TimeUnit unit)
248			throws InterruptedException, ExecutionException, TimeoutException;
249	dl	1.3
250	dl	1.1	}