1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 * Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/publicdomain/zero/1.0/
34 */
35
36 package java.util.concurrent;
37
38 import static java.util.concurrent.TimeUnit.NANOSECONDS;
39
40 import java.util.ArrayList;
41 import java.util.Collection;
42 import java.util.Iterator;
43 import java.util.List;
44
45 /**
46 * Provides default implementations of {@link ExecutorService}
47 * execution methods. This class implements the {@code submit},
48 * {@code invokeAny} and {@code invokeAll} methods using a
49 * {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
50 * to the {@link FutureTask} class provided in this package. For example,
51 * the implementation of {@code submit(Runnable)} creates an
52 * associated {@code RunnableFuture} that is executed and
53 * returned. Subclasses may override the {@code newTaskFor} methods
54 * to return {@code RunnableFuture} implementations other than
55 * {@code FutureTask}.
56 *
57 * <p><b>Extension example</b>. Here is a sketch of a class
58 * that customizes {@link ThreadPoolExecutor} to use
59 * a {@code CustomTask} class instead of the default {@code FutureTask}:
60 * <pre> {@code
61 * public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
62 *
63 * static class CustomTask<V> implements RunnableFuture<V> {...}
64 *
65 * protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
66 * return new CustomTask<V>(c);
67 * }
68 * protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
69 * return new CustomTask<V>(r, v);
70 * }
71 * // ... add constructors, etc.
72 * }}</pre>
73 *
74 * @since 1.5
75 * @author Doug Lea
76 */
77 public abstract class AbstractExecutorService implements ExecutorService {
78
79 /**
80 * Constructor for subclasses to call.
81 */
82 public AbstractExecutorService() {}
83
84 /**
85 * Returns a {@code RunnableFuture} for the given runnable and default
86 * value.
87 *
88 * @param runnable the runnable task being wrapped
89 * @param value the default value for the returned future
90 * @param <T> the type of the given value
91 * @return a {@code RunnableFuture} which, when run, will run the
92 * underlying runnable and which, as a {@code Future}, will yield
93 * the given value as its result and provide for cancellation of
94 * the underlying task
95 * @since 1.6
96 */
97 protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
98 return new FutureTask<T>(runnable, value);
99 }
100
101 /**
102 * Returns a {@code RunnableFuture} for the given callable task.
103 *
104 * @param callable the callable task being wrapped
105 * @param <T> the type of the callable's result
106 * @return a {@code RunnableFuture} which, when run, will call the
107 * underlying callable and which, as a {@code Future}, will yield
108 * the callable's result as its result and provide for
109 * cancellation of the underlying task
110 * @since 1.6
111 */
112 protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
113 return new FutureTask<T>(callable);
114 }
115
116 /**
117 * @throws RejectedExecutionException {@inheritDoc}
118 * @throws NullPointerException {@inheritDoc}
119 */
120 public Future<?> submit(Runnable task) {
121 if (task == null) throw new NullPointerException();
122 RunnableFuture<Void> ftask = newTaskFor(task, null);
123 execute(ftask);
124 return ftask;
125 }
126
127 /**
128 * @throws RejectedExecutionException {@inheritDoc}
129 * @throws NullPointerException {@inheritDoc}
130 */
131 public <T> Future<T> submit(Runnable task, T result) {
132 if (task == null) throw new NullPointerException();
133 RunnableFuture<T> ftask = newTaskFor(task, result);
134 execute(ftask);
135 return ftask;
136 }
137
138 /**
139 * @throws RejectedExecutionException {@inheritDoc}
140 * @throws NullPointerException {@inheritDoc}
141 */
142 public <T> Future<T> submit(Callable<T> task) {
143 if (task == null) throw new NullPointerException();
144 RunnableFuture<T> ftask = newTaskFor(task);
145 execute(ftask);
146 return ftask;
147 }
148
149 /**
150 * the main mechanics of invokeAny.
151 */
152 private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
153 boolean timed, long nanos)
154 throws InterruptedException, ExecutionException, TimeoutException {
155 if (tasks == null)
156 throw new NullPointerException();
157 int ntasks = tasks.size();
158 if (ntasks == 0)
159 throw new IllegalArgumentException();
160 ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
161 ExecutorCompletionService<T> ecs =
162 new ExecutorCompletionService<T>(this);
163
164 // For efficiency, especially in executors with limited
165 // parallelism, check to see if previously submitted tasks are
166 // done before submitting more of them. This interleaving
167 // plus the exception mechanics account for messiness of main
168 // loop.
169
170 try {
171 // Record exceptions so that if we fail to obtain any
172 // result, we can throw the last exception we got.
173 ExecutionException ee = null;
174 final long deadline = timed ? System.nanoTime() + nanos : 0L;
175 Iterator<? extends Callable<T>> it = tasks.iterator();
176
177 // Start one task for sure; the rest incrementally
178 futures.add(ecs.submit(it.next()));
179 --ntasks;
180 int active = 1;
181
182 for (;;) {
183 Future<T> f = ecs.poll();
184 if (f == null) {
185 if (ntasks > 0) {
186 --ntasks;
187 futures.add(ecs.submit(it.next()));
188 ++active;
189 }
190 else if (active == 0)
191 break;
192 else if (timed) {
193 f = ecs.poll(nanos, NANOSECONDS);
194 if (f == null)
195 throw new TimeoutException();
196 nanos = deadline - System.nanoTime();
197 }
198 else
199 f = ecs.take();
200 }
201 if (f != null) {
202 --active;
203 try {
204 return f.get();
205 } catch (ExecutionException eex) {
206 ee = eex;
207 } catch (RuntimeException rex) {
208 ee = new ExecutionException(rex);
209 }
210 }
211 }
212
213 if (ee == null)
214 ee = new ExecutionException();
215 throw ee;
216
217 } finally {
218 cancelAll(futures);
219 }
220 }
221
222 public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
223 throws InterruptedException, ExecutionException {
224 try {
225 return doInvokeAny(tasks, false, 0);
226 } catch (TimeoutException cannotHappen) {
227 assert false;
228 return null;
229 }
230 }
231
232 public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
233 long timeout, TimeUnit unit)
234 throws InterruptedException, ExecutionException, TimeoutException {
235 return doInvokeAny(tasks, true, unit.toNanos(timeout));
236 }
237
238 public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
239 throws InterruptedException {
240 if (tasks == null)
241 throw new NullPointerException();
242 ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
243 try {
244 for (Callable<T> t : tasks) {
245 RunnableFuture<T> f = newTaskFor(t);
246 futures.add(f);
247 execute(f);
248 }
249 for (int i = 0, size = futures.size(); i < size; i++) {
250 Future<T> f = futures.get(i);
251 if (!f.isDone()) {
252 try { f.get(); }
253 catch (CancellationException | ExecutionException ignore) {}
254 }
255 }
256 return futures;
257 } catch (Throwable t) {
258 cancelAll(futures);
259 throw t;
260 }
261 }
262
263 public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
264 long timeout, TimeUnit unit)
265 throws InterruptedException {
266 if (tasks == null)
267 throw new NullPointerException();
268 final long nanos = unit.toNanos(timeout);
269 final long deadline = System.nanoTime() + nanos;
270 ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
271 int j = 0;
272 timedOut: try {
273 for (Callable<T> t : tasks)
274 futures.add(newTaskFor(t));
275
276 final int size = futures.size();
277
278 // Interleave time checks and calls to execute in case
279 // executor doesn't have any/much parallelism.
280 for (int i = 0; i < size; i++) {
281 if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
282 break timedOut;
283 execute((Runnable)futures.get(i));
284 }
285
286 for (; j < size; j++) {
287 Future<T> f = futures.get(j);
288 if (!f.isDone()) {
289 try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
290 catch (CancellationException | ExecutionException ignore) {}
291 catch (TimeoutException timedOut) {
292 break timedOut;
293 }
294 }
295 }
296 return futures;
297 } catch (Throwable t) {
298 cancelAll(futures);
299 throw t;
300 }
301 // Timed out before all the tasks could be completed; cancel remaining
302 cancelAll(futures, j);
303 return futures;
304 }
305
306 private static <T> void cancelAll(ArrayList<Future<T>> futures) {
307 cancelAll(futures, 0);
308 }
309
310 /** Cancels all futures with index at least j. */
311 private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
312 for (int size = futures.size(); j < size; j++)
313 futures.get(j).cancel(true);
314 }
315 }