util/concurrent/AbstractExecutorService.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/publicdomain/zero/1.0/
 */

package java.util.concurrent;

import static java.util.concurrent.TimeUnit.NANOSECONDS;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

/**
 * Provides default implementations of {@link ExecutorService}
 * execution methods. This class implements the {@code submit},
 * {@code invokeAny} and {@code invokeAll} methods using a
 * {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
 * to the {@link FutureTask} class provided in this package.  For example,
 * the implementation of {@code submit(Runnable)} creates an
 * associated {@code RunnableFuture} that is executed and
 * returned. Subclasses may override the {@code newTaskFor} methods
 * to return {@code RunnableFuture} implementations other than
 * {@code FutureTask}.
 *
 * <p><b>Extension example</b>. Here is a sketch of a class
 * that customizes {@link ThreadPoolExecutor} to use
 * a {@code CustomTask} class instead of the default {@code FutureTask}:
 * <pre> {@code
 * public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
 *
 *   static class CustomTask<V> implements RunnableFuture<V> {...}
 *
 *   protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
 *       return new CustomTask<V>(c);
 *   }
 *   protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
 *       return new CustomTask<V>(r, v);
 *   }
 *   // ... add constructors, etc.
 * }}</pre>
 *
 * @since 1.5
 * @author Doug Lea
 */
public abstract class AbstractExecutorService implements ExecutorService {

    /**
     * Returns a {@code RunnableFuture} for the given runnable and default
     * value.
     *
     * @param runnable the runnable task being wrapped
     * @param value the default value for the returned future
     * @param <T> the type of the given value
     * @return a {@code RunnableFuture} which, when run, will run the
     * underlying runnable and which, as a {@code Future}, will yield
     * the given value as its result and provide for cancellation of
     * the underlying task
     * @since 1.6
     */
    protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
        return new FutureTask<T>(runnable, value);
    }

    /**
     * Returns a {@code RunnableFuture} for the given callable task.
     *
     * @param callable the callable task being wrapped
     * @param <T> the type of the callable's result
     * @return a {@code RunnableFuture} which, when run, will call the
     * underlying callable and which, as a {@code Future}, will yield
     * the callable's result as its result and provide for
     * cancellation of the underlying task
     * @since 1.6
     */
    protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
        return new FutureTask<T>(callable);
    }

    /**
     * @throws RejectedExecutionException {@inheritDoc}
     * @throws NullPointerException       {@inheritDoc}
     */
    public Future<?> submit(Runnable task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<Void> ftask = newTaskFor(task, null);
        execute(ftask);
        return ftask;
    }

    /**
     * @throws RejectedExecutionException {@inheritDoc}
     * @throws NullPointerException       {@inheritDoc}
     */
    public <T> Future<T> submit(Runnable task, T result) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<T> ftask = newTaskFor(task, result);
        execute(ftask);
        return ftask;
    }

    /**
     * @throws RejectedExecutionException {@inheritDoc}
     * @throws NullPointerException       {@inheritDoc}
     */
    public <T> Future<T> submit(Callable<T> task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<T> ftask = newTaskFor(task);
        execute(ftask);
        return ftask;
    }

    /**
     * the main mechanics of invokeAny.
     */
    private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
                              boolean timed, long nanos)
        throws InterruptedException, ExecutionException, TimeoutException {
        if (tasks == null)
            throw new NullPointerException();
        int ntasks = tasks.size();
        if (ntasks == 0)
            throw new IllegalArgumentException();
        ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
        ExecutorCompletionService<T> ecs =
            new ExecutorCompletionService<T>(this);

        // For efficiency, especially in executors with limited
        // parallelism, check to see if previously submitted tasks are
        // done before submitting more of them. This interleaving
        // plus the exception mechanics account for messiness of main
        // loop.

        try {
            // Record exceptions so that if we fail to obtain any
            // result, we can throw the last exception we got.
            ExecutionException ee = null;
            final long deadline = timed ? System.nanoTime() + nanos : 0L;
            Iterator<? extends Callable<T>> it = tasks.iterator();

            // Start one task for sure; the rest incrementally
            futures.add(ecs.submit(it.next()));
            --ntasks;
            int active = 1;

            for (;;) {
                Future<T> f = ecs.poll();
                if (f == null) {
                    if (ntasks > 0) {
                        --ntasks;
                        futures.add(ecs.submit(it.next()));
                        ++active;
                    }
                    else if (active == 0)
                        break;
                    else if (timed) {
                        f = ecs.poll(nanos, NANOSECONDS);
                        if (f == null)
                            throw new TimeoutException();
                        nanos = deadline - System.nanoTime();
                    }
                    else
                        f = ecs.take();
                }
                if (f != null) {
                    --active;
                    try {
                        return f.get();
                    } catch (ExecutionException eex) {
                        ee = eex;
                    } catch (RuntimeException rex) {
                        ee = new ExecutionException(rex);
                    }
                }
            }

            if (ee == null)
                ee = new ExecutionException();
            throw ee;

        } finally {
            cancelAll(futures);
        }
    }

    public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
        throws InterruptedException, ExecutionException {
        try {
            return doInvokeAny(tasks, false, 0);
        } catch (TimeoutException cannotHappen) {
            assert false;
            return null;
        }
    }

    public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
                           long timeout, TimeUnit unit)
        throws InterruptedException, ExecutionException, TimeoutException {
        return doInvokeAny(tasks, true, unit.toNanos(timeout));
    }

    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
        throws InterruptedException {
        if (tasks == null)
            throw new NullPointerException();
        ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
        try {
            for (Callable<T> t : tasks) {
                RunnableFuture<T> f = newTaskFor(t);
                futures.add(f);
                execute(f);
            }
            for (int i = 0, size = futures.size(); i < size; i++) {
                Future<T> f = futures.get(i);
                if (!f.isDone()) {
                    try { f.get(); }
                    catch (CancellationException | ExecutionException ignore) {}
                }
            }
            return futures;
        } catch (Throwable t) {
            cancelAll(futures);
            throw t;
        }
    }

    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
                                         long timeout, TimeUnit unit)
        throws InterruptedException {
        if (tasks == null)
            throw new NullPointerException();
        final long nanos = unit.toNanos(timeout);
        final long deadline = System.nanoTime() + nanos;
        ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
        int j = 0;
        timedOut: try {
            for (Callable<T> t : tasks)
                futures.add(newTaskFor(t));

            final int size = futures.size();

            // Interleave time checks and calls to execute in case
            // executor doesn't have any/much parallelism.
            for (int i = 0; i < size; i++) {
                if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
                    break timedOut;
                execute((Runnable)futures.get(i));
            }

            for (; j < size; j++) {
                Future<T> f = futures.get(j);
                if (!f.isDone()) {
                    try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
                    catch (CancellationException | ExecutionException ignore) {}
                    catch (TimeoutException timedOut) {
                        break timedOut;
                    }
                }
            }
            return futures;
        } catch (Throwable t) {
            cancelAll(futures);
            throw t;
        }
        // Timed out before all the tasks could be completed; cancel remaining
        cancelAll(futures, j);
        return futures;
    }

    private static <T> void cancelAll(ArrayList<Future<T>> futures) {
        cancelAll(futures, 0);
    }

    /** Cancels all futures with index at least j. */
    private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
        for (int size = futures.size(); j < size; j++)
            futures.get(j).cancel(true);
    }
}
Revision:	1.52
Committed:	Sun Jan 7 23:11:06 2018 UTC (6 years, 5 months ago) by jsr166
Branch:	MAIN
Changes since 1.51:	+2 -4 lines
Log Message:	use multi-catch
#	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/publicdomain/zero/1.0/
5	*/
6
7	package java.util.concurrent;
8
9	import static java.util.concurrent.TimeUnit.NANOSECONDS;
10
11	import java.util.ArrayList;
12	import java.util.Collection;
13	import java.util.Iterator;
14	import java.util.List;
15
16	/**
17	* Provides default implementations of {@link ExecutorService}
18	* execution methods. This class implements the {@code submit},
19	* {@code invokeAny} and {@code invokeAll} methods using a
20	* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
21	* to the {@link FutureTask} class provided in this package. For example,
22	* the implementation of {@code submit(Runnable)} creates an
23	* associated {@code RunnableFuture} that is executed and
24	* returned. Subclasses may override the {@code newTaskFor} methods
25	* to return {@code RunnableFuture} implementations other than
26	* {@code FutureTask}.
27	*
28	* <p><b>Extension example</b>. Here is a sketch of a class
29	* that customizes {@link ThreadPoolExecutor} to use
30	* a {@code CustomTask} class instead of the default {@code FutureTask}:
31	* <pre> {@code
32	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
33	*
34	* static class CustomTask<V> implements RunnableFuture<V> {...}
35	*
36	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
37	* return new CustomTask<V>(c);
38	* }
39	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
40	* return new CustomTask<V>(r, v);
41	* }
42	* // ... add constructors, etc.
43	* }}</pre>
44	*
45	* @since 1.5
46	* @author Doug Lea
47	*/
48	public abstract class AbstractExecutorService implements ExecutorService {
49
50	/**
51	* Returns a {@code RunnableFuture} for the given runnable and default
52	* value.
53	*
54	* @param runnable the runnable task being wrapped
55	* @param value the default value for the returned future
56	* @param <T> the type of the given value
57	* @return a {@code RunnableFuture} which, when run, will run the
58	* underlying runnable and which, as a {@code Future}, will yield
59	* the given value as its result and provide for cancellation of
60	* the underlying task
61	* @since 1.6
62	*/
63	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
64	return new FutureTask<T>(runnable, value);
65	}
66
67	/**
68	* Returns a {@code RunnableFuture} for the given callable task.
69	*
70	* @param callable the callable task being wrapped
71	* @param <T> the type of the callable's result
72	* @return a {@code RunnableFuture} which, when run, will call the
73	* underlying callable and which, as a {@code Future}, will yield
74	* the callable's result as its result and provide for
75	* cancellation of the underlying task
76	* @since 1.6
77	*/
78	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
79	return new FutureTask<T>(callable);
80	}
81
82	/**
83	* @throws RejectedExecutionException {@inheritDoc}
84	* @throws NullPointerException {@inheritDoc}
85	*/
86	public Future<?> submit(Runnable task) {
87	if (task == null) throw new NullPointerException();
88	RunnableFuture<Void> ftask = newTaskFor(task, null);
89	execute(ftask);
90	return ftask;
91	}
92
93	/**
94	* @throws RejectedExecutionException {@inheritDoc}
95	* @throws NullPointerException {@inheritDoc}
96	*/
97	public <T> Future<T> submit(Runnable task, T result) {
98	if (task == null) throw new NullPointerException();
99	RunnableFuture<T> ftask = newTaskFor(task, result);
100	execute(ftask);
101	return ftask;
102	}
103
104	/**
105	* @throws RejectedExecutionException {@inheritDoc}
106	* @throws NullPointerException {@inheritDoc}
107	*/
108	public <T> Future<T> submit(Callable<T> task) {
109	if (task == null) throw new NullPointerException();
110	RunnableFuture<T> ftask = newTaskFor(task);
111	execute(ftask);
112	return ftask;
113	}
114
115	/**
116	* the main mechanics of invokeAny.
117	*/
118	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
119	boolean timed, long nanos)
120	throws InterruptedException, ExecutionException, TimeoutException {
121	if (tasks == null)
122	throw new NullPointerException();
123	int ntasks = tasks.size();
124	if (ntasks == 0)
125	throw new IllegalArgumentException();
126	ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
127	ExecutorCompletionService<T> ecs =
128	new ExecutorCompletionService<T>(this);
129
130	// For efficiency, especially in executors with limited
131	// parallelism, check to see if previously submitted tasks are
132	// done before submitting more of them. This interleaving
133	// plus the exception mechanics account for messiness of main
134	// loop.
135
136	try {
137	// Record exceptions so that if we fail to obtain any
138	// result, we can throw the last exception we got.
139	ExecutionException ee = null;
140	final long deadline = timed ? System.nanoTime() + nanos : 0L;
141	Iterator<? extends Callable<T>> it = tasks.iterator();
142
143	// Start one task for sure; the rest incrementally
144	futures.add(ecs.submit(it.next()));
145	--ntasks;
146	int active = 1;
147
148	for (;;) {
149	Future<T> f = ecs.poll();
150	if (f == null) {
151	if (ntasks > 0) {
152	--ntasks;
153	futures.add(ecs.submit(it.next()));
154	++active;
155	}
156	else if (active == 0)
157	break;
158	else if (timed) {
159	f = ecs.poll(nanos, NANOSECONDS);
160	if (f == null)
161	throw new TimeoutException();
162	nanos = deadline - System.nanoTime();
163	}
164	else
165	f = ecs.take();
166	}
167	if (f != null) {
168	--active;
169	try {
170	return f.get();
171	} catch (ExecutionException eex) {
172	ee = eex;
173	} catch (RuntimeException rex) {
174	ee = new ExecutionException(rex);
175	}
176	}
177	}
178
179	if (ee == null)
180	ee = new ExecutionException();
181	throw ee;
182
183	} finally {
184	cancelAll(futures);
185	}
186	}
187
188	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
189	throws InterruptedException, ExecutionException {
190	try {
191	return doInvokeAny(tasks, false, 0);
192	} catch (TimeoutException cannotHappen) {
193	assert false;
194	return null;
195	}
196	}
197
198	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
199	long timeout, TimeUnit unit)
200	throws InterruptedException, ExecutionException, TimeoutException {
201	return doInvokeAny(tasks, true, unit.toNanos(timeout));
202	}
203
204	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
205	throws InterruptedException {
206	if (tasks == null)
207	throw new NullPointerException();
208	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
209	try {
210	for (Callable<T> t : tasks) {
211	RunnableFuture<T> f = newTaskFor(t);
212	futures.add(f);
213	execute(f);
214	}
215	for (int i = 0, size = futures.size(); i < size; i++) {
216	Future<T> f = futures.get(i);
217	if (!f.isDone()) {
218	try { f.get(); }
219	catch (CancellationException \| ExecutionException ignore) {}
220	}
221	}
222	return futures;
223	} catch (Throwable t) {
224	cancelAll(futures);
225	throw t;
226	}
227	}
228
229	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
230	long timeout, TimeUnit unit)
231	throws InterruptedException {
232	if (tasks == null)
233	throw new NullPointerException();
234	final long nanos = unit.toNanos(timeout);
235	final long deadline = System.nanoTime() + nanos;
236	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
237	int j = 0;
238	timedOut: try {
239	for (Callable<T> t : tasks)
240	futures.add(newTaskFor(t));
241
242	final int size = futures.size();
243
244	// Interleave time checks and calls to execute in case
245	// executor doesn't have any/much parallelism.
246	for (int i = 0; i < size; i++) {
247	if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
248	break timedOut;
249	execute((Runnable)futures.get(i));
250	}
251
252	for (; j < size; j++) {
253	Future<T> f = futures.get(j);
254	if (!f.isDone()) {
255	try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
256	catch (CancellationException \| ExecutionException ignore) {}
257	catch (TimeoutException timedOut) {
258	break timedOut;
259	}
260	}
261	}
262	return futures;
263	} catch (Throwable t) {
264	cancelAll(futures);
265	throw t;
266	}
267	// Timed out before all the tasks could be completed; cancel remaining
268	cancelAll(futures, j);
269	return futures;
270	}
271
272	private static <T> void cancelAll(ArrayList<Future<T>> futures) {
273	cancelAll(futures, 0);
274	}
275
276	/** Cancels all futures with index at least j. */
277	private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
278	for (int size = futures.size(); j < size; j++)
279	futures.get(j).cancel(true);
280	}
281	}