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 |
jsr166 |
1.51 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
5 |
dl |
1.1 |
*/ |
6 |
|
|
|
7 |
|
|
package java.util.concurrent; |
8 |
|
|
import java.util.List; |
9 |
dl |
1.15 |
import java.util.Collection; |
10 |
dl |
1.1 |
|
11 |
|
|
/** |
12 |
dl |
1.25 |
* An {@link Executor} that provides methods to manage termination and |
13 |
dl |
1.20 |
* methods that can produce a {@link Future} for tracking progress of |
14 |
jsr166 |
1.33 |
* one or more asynchronous tasks. |
15 |
dl |
1.17 |
* |
16 |
jsr166 |
1.58 |
* <p>An {@code ExecutorService} can be shut down, which will cause |
17 |
dl |
1.47 |
* it to reject new tasks. Two different methods are provided for |
18 |
jsr166 |
1.58 |
* shutting down an {@code ExecutorService}. The {@link #shutdown} |
19 |
dl |
1.47 |
* method will allow previously submitted tasks to execute before |
20 |
|
|
* terminating, while the {@link #shutdownNow} method prevents waiting |
21 |
|
|
* tasks from starting and attempts to stop currently executing tasks. |
22 |
|
|
* Upon termination, an executor has no tasks actively executing, no |
23 |
|
|
* tasks awaiting execution, and no new tasks can be submitted. An |
24 |
jsr166 |
1.58 |
* unused {@code ExecutorService} should be shut down to allow |
25 |
dl |
1.47 |
* reclamation of its resources. |
26 |
dl |
1.1 |
* |
27 |
jsr166 |
1.58 |
* <p>Method {@code submit} extends base method {@link |
28 |
dl |
1.20 |
* Executor#execute} by creating and returning a {@link Future} that |
29 |
|
|
* can be used to cancel execution and/or wait for completion. |
30 |
jsr166 |
1.58 |
* Methods {@code invokeAny} and {@code invokeAll} perform the most |
31 |
dl |
1.20 |
* commonly useful forms of bulk execution, executing a collection of |
32 |
|
|
* tasks and then waiting for at least one, or all, to |
33 |
|
|
* complete. (Class {@link ExecutorCompletionService} can be used to |
34 |
|
|
* write customized variants of these methods.) |
35 |
dl |
1.17 |
* |
36 |
dl |
1.7 |
* <p>The {@link Executors} class provides factory methods for the |
37 |
|
|
* executor services provided in this package. |
38 |
dl |
1.1 |
* |
39 |
dl |
1.47 |
* <h3>Usage Examples</h3> |
40 |
dl |
1.23 |
* |
41 |
|
|
* Here is a sketch of a network service in which threads in a thread |
42 |
|
|
* pool service incoming requests. It uses the preconfigured {@link |
43 |
|
|
* Executors#newFixedThreadPool} factory method: |
44 |
|
|
* |
45 |
jsr166 |
1.53 |
* <pre> {@code |
46 |
dl |
1.47 |
* class NetworkService implements Runnable { |
47 |
jsr166 |
1.37 |
* private final ServerSocket serverSocket; |
48 |
|
|
* private final ExecutorService pool; |
49 |
dl |
1.23 |
* |
50 |
jsr166 |
1.37 |
* public NetworkService(int port, int poolSize) |
51 |
|
|
* throws IOException { |
52 |
|
|
* serverSocket = new ServerSocket(port); |
53 |
|
|
* pool = Executors.newFixedThreadPool(poolSize); |
54 |
|
|
* } |
55 |
jsr166 |
1.33 |
* |
56 |
dl |
1.47 |
* public void run() { // run the service |
57 |
jsr166 |
1.37 |
* try { |
58 |
|
|
* for (;;) { |
59 |
|
|
* pool.execute(new Handler(serverSocket.accept())); |
60 |
|
|
* } |
61 |
|
|
* } catch (IOException ex) { |
62 |
|
|
* pool.shutdown(); |
63 |
|
|
* } |
64 |
|
|
* } |
65 |
|
|
* } |
66 |
dl |
1.23 |
* |
67 |
jsr166 |
1.37 |
* class Handler implements Runnable { |
68 |
|
|
* private final Socket socket; |
69 |
|
|
* Handler(Socket socket) { this.socket = socket; } |
70 |
|
|
* public void run() { |
71 |
dl |
1.47 |
* // read and service request on socket |
72 |
|
|
* } |
73 |
jsr166 |
1.53 |
* }}</pre> |
74 |
dl |
1.47 |
* |
75 |
jsr166 |
1.58 |
* The following method shuts down an {@code ExecutorService} in two phases, |
76 |
|
|
* first by calling {@code shutdown} to reject incoming tasks, and then |
77 |
|
|
* calling {@code shutdownNow}, if necessary, to cancel any lingering tasks: |
78 |
dl |
1.47 |
* |
79 |
jsr166 |
1.53 |
* <pre> {@code |
80 |
dl |
1.47 |
* void shutdownAndAwaitTermination(ExecutorService pool) { |
81 |
|
|
* pool.shutdown(); // Disable new tasks from being submitted |
82 |
|
|
* try { |
83 |
|
|
* // Wait a while for existing tasks to terminate |
84 |
|
|
* if (!pool.awaitTermination(60, TimeUnit.SECONDS)) { |
85 |
|
|
* pool.shutdownNow(); // Cancel currently executing tasks |
86 |
|
|
* // Wait a while for tasks to respond to being cancelled |
87 |
|
|
* if (!pool.awaitTermination(60, TimeUnit.SECONDS)) |
88 |
|
|
* System.err.println("Pool did not terminate"); |
89 |
|
|
* } |
90 |
|
|
* } catch (InterruptedException ie) { |
91 |
jsr166 |
1.48 |
* // (Re-)Cancel if current thread also interrupted |
92 |
|
|
* pool.shutdownNow(); |
93 |
|
|
* // Preserve interrupt status |
94 |
|
|
* Thread.currentThread().interrupt(); |
95 |
jsr166 |
1.37 |
* } |
96 |
jsr166 |
1.53 |
* }}</pre> |
97 |
brian |
1.40 |
* |
98 |
jsr166 |
1.43 |
* <p>Memory consistency effects: Actions in a thread prior to the |
99 |
|
|
* submission of a {@code Runnable} or {@code Callable} task to an |
100 |
|
|
* {@code ExecutorService} |
101 |
|
|
* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> |
102 |
|
|
* any actions taken by that task, which in turn <i>happen-before</i> the |
103 |
|
|
* result is retrieved via {@code Future.get()}. |
104 |
brian |
1.40 |
* |
105 |
dl |
1.1 |
* @since 1.5 |
106 |
dl |
1.5 |
* @author Doug Lea |
107 |
dl |
1.1 |
*/ |
108 |
|
|
public interface ExecutorService extends Executor { |
109 |
tim |
1.8 |
|
110 |
dl |
1.17 |
/** |
111 |
|
|
* Initiates an orderly shutdown in which previously submitted |
112 |
jsr166 |
1.37 |
* tasks are executed, but no new tasks will be accepted. |
113 |
|
|
* Invocation has no additional effect if already shut down. |
114 |
|
|
* |
115 |
jsr166 |
1.49 |
* <p>This method does not wait for previously submitted tasks to |
116 |
|
|
* complete execution. Use {@link #awaitTermination awaitTermination} |
117 |
|
|
* to do that. |
118 |
|
|
* |
119 |
dl |
1.17 |
* @throws SecurityException if a security manager exists and |
120 |
jsr166 |
1.37 |
* shutting down this ExecutorService may manipulate |
121 |
|
|
* threads that the caller is not permitted to modify |
122 |
|
|
* because it does not hold {@link |
123 |
jsr166 |
1.58 |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
124 |
|
|
* or the security manager's {@code checkAccess} method |
125 |
jsr166 |
1.37 |
* denies access. |
126 |
dl |
1.17 |
*/ |
127 |
|
|
void shutdown(); |
128 |
|
|
|
129 |
|
|
/** |
130 |
|
|
* Attempts to stop all actively executing tasks, halts the |
131 |
jsr166 |
1.49 |
* processing of waiting tasks, and returns a list of the tasks |
132 |
|
|
* that were awaiting execution. |
133 |
|
|
* |
134 |
|
|
* <p>This method does not wait for actively executing tasks to |
135 |
|
|
* terminate. Use {@link #awaitTermination awaitTermination} to |
136 |
|
|
* do that. |
137 |
jsr166 |
1.33 |
* |
138 |
dl |
1.17 |
* <p>There are no guarantees beyond best-effort attempts to stop |
139 |
|
|
* processing actively executing tasks. For example, typical |
140 |
jsr166 |
1.39 |
* implementations will cancel via {@link Thread#interrupt}, so any |
141 |
|
|
* task that fails to respond to interrupts may never terminate. |
142 |
dl |
1.17 |
* |
143 |
|
|
* @return list of tasks that never commenced execution |
144 |
|
|
* @throws SecurityException if a security manager exists and |
145 |
jsr166 |
1.37 |
* shutting down this ExecutorService may manipulate |
146 |
|
|
* threads that the caller is not permitted to modify |
147 |
|
|
* because it does not hold {@link |
148 |
jsr166 |
1.58 |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
149 |
|
|
* or the security manager's {@code checkAccess} method |
150 |
jsr166 |
1.37 |
* denies access. |
151 |
dl |
1.17 |
*/ |
152 |
|
|
List<Runnable> shutdownNow(); |
153 |
|
|
|
154 |
|
|
/** |
155 |
jsr166 |
1.58 |
* Returns {@code true} if this executor has been shut down. |
156 |
dl |
1.17 |
* |
157 |
jsr166 |
1.58 |
* @return {@code true} if this executor has been shut down |
158 |
dl |
1.17 |
*/ |
159 |
|
|
boolean isShutdown(); |
160 |
|
|
|
161 |
|
|
/** |
162 |
jsr166 |
1.58 |
* Returns {@code true} if all tasks have completed following shut down. |
163 |
|
|
* Note that {@code isTerminated} is never {@code true} unless |
164 |
|
|
* either {@code shutdown} or {@code shutdownNow} was called first. |
165 |
dl |
1.17 |
* |
166 |
jsr166 |
1.58 |
* @return {@code true} if all tasks have completed following shut down |
167 |
dl |
1.17 |
*/ |
168 |
|
|
boolean isTerminated(); |
169 |
|
|
|
170 |
|
|
/** |
171 |
|
|
* Blocks until all tasks have completed execution after a shutdown |
172 |
|
|
* request, or the timeout occurs, or the current thread is |
173 |
jsr166 |
1.36 |
* interrupted, whichever happens first. |
174 |
dl |
1.17 |
* |
175 |
|
|
* @param timeout the maximum time to wait |
176 |
|
|
* @param unit the time unit of the timeout argument |
177 |
jsr166 |
1.58 |
* @return {@code true} if this executor terminated and |
178 |
|
|
* {@code false} if the timeout elapsed before termination |
179 |
dl |
1.17 |
* @throws InterruptedException if interrupted while waiting |
180 |
|
|
*/ |
181 |
|
|
boolean awaitTermination(long timeout, TimeUnit unit) |
182 |
|
|
throws InterruptedException; |
183 |
|
|
|
184 |
tim |
1.8 |
/** |
185 |
dl |
1.30 |
* Submits a value-returning task for execution and returns a |
186 |
dl |
1.31 |
* Future representing the pending results of the task. The |
187 |
jsr166 |
1.58 |
* Future's {@code get} method will return the task's result upon |
188 |
jsr166 |
1.37 |
* successful completion. |
189 |
tim |
1.8 |
* |
190 |
dl |
1.19 |
* <p> |
191 |
dl |
1.20 |
* If you would like to immediately block waiting |
192 |
dl |
1.19 |
* for a task, you can use constructions of the form |
193 |
jsr166 |
1.58 |
* {@code result = exec.submit(aCallable).get();} |
194 |
dl |
1.20 |
* |
195 |
jsr166 |
1.56 |
* <p>Note: The {@link Executors} class includes a set of methods |
196 |
dl |
1.20 |
* that can convert some other common closure-like objects, |
197 |
|
|
* for example, {@link java.security.PrivilegedAction} to |
198 |
|
|
* {@link Callable} form so they can be submitted. |
199 |
|
|
* |
200 |
tim |
1.8 |
* @param task the task to submit |
201 |
|
|
* @return a Future representing pending completion of the task |
202 |
jsr166 |
1.37 |
* @throws RejectedExecutionException if the task cannot be |
203 |
|
|
* scheduled for execution |
204 |
|
|
* @throws NullPointerException if the task is null |
205 |
tim |
1.8 |
*/ |
206 |
|
|
<T> Future<T> submit(Callable<T> task); |
207 |
|
|
|
208 |
|
|
/** |
209 |
dl |
1.30 |
* Submits a Runnable task for execution and returns a Future |
210 |
jsr166 |
1.58 |
* representing that task. The Future's {@code get} method will |
211 |
dl |
1.31 |
* return the given result upon successful completion. |
212 |
dl |
1.20 |
* |
213 |
|
|
* @param task the task to submit |
214 |
|
|
* @param result the result to return |
215 |
dl |
1.31 |
* @return a Future representing pending completion of the task |
216 |
jsr166 |
1.37 |
* @throws RejectedExecutionException if the task cannot be |
217 |
|
|
* scheduled for execution |
218 |
|
|
* @throws NullPointerException if the task is null |
219 |
dl |
1.20 |
*/ |
220 |
|
|
<T> Future<T> submit(Runnable task, T result); |
221 |
|
|
|
222 |
|
|
/** |
223 |
jsr166 |
1.33 |
* Submits a Runnable task for execution and returns a Future |
224 |
jsr166 |
1.58 |
* representing that task. The Future's {@code get} method will |
225 |
|
|
* return {@code null} upon <em>successful</em> completion. |
226 |
dl |
1.1 |
* |
227 |
dl |
1.17 |
* @param task the task to submit |
228 |
dl |
1.31 |
* @return a Future representing pending completion of the task |
229 |
jsr166 |
1.37 |
* @throws RejectedExecutionException if the task cannot be |
230 |
|
|
* scheduled for execution |
231 |
|
|
* @throws NullPointerException if the task is null |
232 |
dl |
1.1 |
*/ |
233 |
dl |
1.18 |
Future<?> submit(Runnable task); |
234 |
dl |
1.15 |
|
235 |
dl |
1.11 |
/** |
236 |
dl |
1.27 |
* Executes the given tasks, returning a list of Futures holding |
237 |
jsr166 |
1.33 |
* their status and results when all complete. |
238 |
jsr166 |
1.58 |
* {@link Future#isDone} is {@code true} for each |
239 |
dl |
1.27 |
* element of the returned list. |
240 |
dl |
1.12 |
* Note that a <em>completed</em> task could have |
241 |
|
|
* terminated either normally or by throwing an exception. |
242 |
dl |
1.21 |
* The results of this method are undefined if the given |
243 |
|
|
* collection is modified while this operation is in progress. |
244 |
jsr166 |
1.37 |
* |
245 |
dl |
1.11 |
* @param tasks the collection of tasks |
246 |
jsr166 |
1.59 |
* @return a list of Futures representing the tasks, in the same |
247 |
jsr166 |
1.37 |
* sequential order as produced by the iterator for the |
248 |
jsr166 |
1.59 |
* given task list, each of which has completed |
249 |
dl |
1.11 |
* @throws InterruptedException if interrupted while waiting, in |
250 |
jsr166 |
1.59 |
* which case unfinished tasks are cancelled |
251 |
jsr166 |
1.58 |
* @throws NullPointerException if tasks or any of its elements are {@code null} |
252 |
jsr166 |
1.37 |
* @throws RejectedExecutionException if any task cannot be |
253 |
|
|
* scheduled for execution |
254 |
dl |
1.11 |
*/ |
255 |
jsr166 |
1.38 |
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) |
256 |
dl |
1.11 |
throws InterruptedException; |
257 |
|
|
|
258 |
|
|
/** |
259 |
dl |
1.27 |
* Executes the given tasks, returning a list of Futures holding |
260 |
jsr166 |
1.33 |
* their status and results |
261 |
dl |
1.15 |
* when all complete or the timeout expires, whichever happens first. |
262 |
jsr166 |
1.58 |
* {@link Future#isDone} is {@code true} for each |
263 |
dl |
1.27 |
* element of the returned list. |
264 |
dl |
1.11 |
* Upon return, tasks that have not completed are cancelled. |
265 |
dl |
1.12 |
* Note that a <em>completed</em> task could have |
266 |
|
|
* terminated either normally or by throwing an exception. |
267 |
dl |
1.21 |
* The results of this method are undefined if the given |
268 |
|
|
* collection is modified while this operation is in progress. |
269 |
jsr166 |
1.37 |
* |
270 |
dl |
1.11 |
* @param tasks the collection of tasks |
271 |
|
|
* @param timeout the maximum time to wait |
272 |
dl |
1.15 |
* @param unit the time unit of the timeout argument |
273 |
jsr166 |
1.37 |
* @return a list of Futures representing the tasks, in the same |
274 |
|
|
* sequential order as produced by the iterator for the |
275 |
|
|
* given task list. If the operation did not time out, |
276 |
|
|
* each task will have completed. If it did time out, some |
277 |
|
|
* of these tasks will not have completed. |
278 |
dl |
1.11 |
* @throws InterruptedException if interrupted while waiting, in |
279 |
jsr166 |
1.37 |
* which case unfinished tasks are cancelled |
280 |
dl |
1.17 |
* @throws NullPointerException if tasks, any of its elements, or |
281 |
jsr166 |
1.58 |
* unit are {@code null} |
282 |
dl |
1.13 |
* @throws RejectedExecutionException if any task cannot be scheduled |
283 |
jsr166 |
1.37 |
* for execution |
284 |
dl |
1.11 |
*/ |
285 |
jsr166 |
1.38 |
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks, |
286 |
jsr166 |
1.33 |
long timeout, TimeUnit unit) |
287 |
dl |
1.11 |
throws InterruptedException; |
288 |
|
|
|
289 |
|
|
/** |
290 |
dl |
1.17 |
* Executes the given tasks, returning the result |
291 |
dl |
1.15 |
* of one that has completed successfully (i.e., without throwing |
292 |
|
|
* an exception), if any do. Upon normal or exceptional return, |
293 |
|
|
* tasks that have not completed are cancelled. |
294 |
dl |
1.21 |
* The results of this method are undefined if the given |
295 |
|
|
* collection is modified while this operation is in progress. |
296 |
jsr166 |
1.37 |
* |
297 |
dl |
1.11 |
* @param tasks the collection of tasks |
298 |
jsr166 |
1.37 |
* @return the result returned by one of the tasks |
299 |
dl |
1.15 |
* @throws InterruptedException if interrupted while waiting |
300 |
jsr166 |
1.50 |
* @throws NullPointerException if tasks or any element task |
301 |
jsr166 |
1.58 |
* subject to execution is {@code null} |
302 |
jsr166 |
1.37 |
* @throws IllegalArgumentException if tasks is empty |
303 |
dl |
1.15 |
* @throws ExecutionException if no task successfully completes |
304 |
|
|
* @throws RejectedExecutionException if tasks cannot be scheduled |
305 |
jsr166 |
1.37 |
* for execution |
306 |
dl |
1.11 |
*/ |
307 |
jsr166 |
1.38 |
<T> T invokeAny(Collection<? extends Callable<T>> tasks) |
308 |
dl |
1.15 |
throws InterruptedException, ExecutionException; |
309 |
dl |
1.11 |
|
310 |
|
|
/** |
311 |
dl |
1.17 |
* Executes the given tasks, returning the result |
312 |
dl |
1.15 |
* of one that has completed successfully (i.e., without throwing |
313 |
|
|
* an exception), if any do before the given timeout elapses. |
314 |
|
|
* Upon normal or exceptional return, tasks that have not |
315 |
|
|
* completed are cancelled. |
316 |
dl |
1.21 |
* The results of this method are undefined if the given |
317 |
|
|
* collection is modified while this operation is in progress. |
318 |
jsr166 |
1.37 |
* |
319 |
dl |
1.11 |
* @param tasks the collection of tasks |
320 |
|
|
* @param timeout the maximum time to wait |
321 |
|
|
* @param unit the time unit of the timeout argument |
322 |
jsr166 |
1.57 |
* @return the result returned by one of the tasks |
323 |
dl |
1.15 |
* @throws InterruptedException if interrupted while waiting |
324 |
jsr166 |
1.50 |
* @throws NullPointerException if tasks, or unit, or any element |
325 |
jsr166 |
1.58 |
* task subject to execution is {@code null} |
326 |
dl |
1.15 |
* @throws TimeoutException if the given timeout elapses before |
327 |
jsr166 |
1.37 |
* any task successfully completes |
328 |
dl |
1.15 |
* @throws ExecutionException if no task successfully completes |
329 |
|
|
* @throws RejectedExecutionException if tasks cannot be scheduled |
330 |
jsr166 |
1.37 |
* for execution |
331 |
dl |
1.11 |
*/ |
332 |
jsr166 |
1.38 |
<T> T invokeAny(Collection<? extends Callable<T>> tasks, |
333 |
jsr166 |
1.33 |
long timeout, TimeUnit unit) |
334 |
dl |
1.15 |
throws InterruptedException, ExecutionException, TimeoutException; |
335 |
dl |
1.1 |
} |