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.
 *
 * @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:	1.22
Committed:	Sat Dec 27 19:26:25 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.21:	+2 -2 lines
Log Message:	Headers reference Creative Commons
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain, as explained at
4	* http://creativecommons.org/licenses/publicdomain
5	*/
6
7	package java.util.concurrent;
8
9	import java.util.List;
10	import java.util.Collection;
11	import java.security.PrivilegedAction;
12	import java.security.PrivilegedExceptionAction;
13
14	/**
15	* 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	*
19	* 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	* executing, no tasks are awaiting execution, and no new tasks can be
23	* submitted.
24	*
25	* <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	*
34	* <p>The {@link Executors} class provides factory methods for the
35	* executor services provided in this package.
36	*
37	* @since 1.5
38	* @author Doug Lea
39	*/
40	public interface ExecutorService extends Executor {
41
42	/**
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	/**
106	* Submits a value-returning task for execution and returns a Future
107	* representing the pending results of the task.
108	*
109	* <p>
110	* If you would like to immediately block waiting
111	* for a task, you can use constructions of the form
112	* <tt>result = exec.submit(aCallable).get();</tt>
113	*
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	* @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	* @throws NullPointerException if task null
124	*/
125	<T> Future<T> submit(Callable<T> task);
126
127	/**
128	* Submits a Runnable task for execution and returns a Future
129	* 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	* representing that task.
146	*
147	* @param task the task to submit
148	* @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	* @throws RejectedExecutionException if task cannot be scheduled
152	* for execution
153	* @throws NullPointerException if task null
154	*/
155	Future<?> submit(Runnable task);
156
157	/**
158	* Executes the given tasks, returning their results
159	* when all complete.
160	* Note that a <em>completed</em> task could have
161	* terminated either normally or by throwing an exception.
162	* The results of this method are undefined if the given
163	* collection is modified while this operation is in progress.
164	* @param tasks the collection of tasks
165	* @return A list of Futures representing the tasks, in the same
166	* sequential order as produced by the iterator for the given task
167	* list, each of which has completed.
168	* @throws InterruptedException if interrupted while waiting, in
169	* which case unfinished tasks are cancelled.
170	* @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	*/
174
175	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
176	throws InterruptedException;
177
178	/**
179	* Executes the given tasks, returning their results
180	* when all complete or the timeout expires, whichever happens first.
181	* Upon return, tasks that have not completed are cancelled.
182	* Note that a <em>completed</em> task could have
183	* terminated either normally or by throwing an exception.
184	* The results of this method are undefined if the given
185	* collection is modified while this operation is in progress.
186	* @param tasks the collection of tasks
187	* @param timeout the maximum time to wait
188	* @param unit the time unit of the timeout argument
189	* @return A list of Futures representing the tasks, in the same
190	* 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	* @throws InterruptedException if interrupted while waiting, in
195	* which case unfinished tasks are cancelled.
196	* @throws NullPointerException if tasks, any of its elements, or
197	* unit are <tt>null</tt>
198	* @throws RejectedExecutionException if any task cannot be scheduled
199	* for execution
200	*/
201	<T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
202	long timeout, TimeUnit unit)
203	throws InterruptedException;
204
205	/**
206	* Executes the given tasks, returning the result
207	* 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	* The results of this method are undefined if the given
211	* collection is modified while this operation is in progress.
212	* @param tasks the collection of tasks
213	* @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	* for execution
221	*/
222	<T> T invokeAny(Collection<Callable<T>> tasks)
223	throws InterruptedException, ExecutionException;
224
225	/**
226	* Executes the given tasks, returning the result
227	* 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	* The results of this method are undefined if the given
232	* collection is modified while this operation is in progress.
233	* @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	* @return The result returned by one of the tasks.
237	* @throws InterruptedException if interrupted while waiting
238	* @throws NullPointerException if tasks, any of its elements, or
239	* 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	* for execution
245	*/
246	<T> T invokeAny(Collection<Callable<T>> tasks,
247	long timeout, TimeUnit unit)
248	throws InterruptedException, ExecutionException, TimeoutException;
249
250	}