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 java.util.*;

/**
 * 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 returned future's 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
     * @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<Future<T>>(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, TimeUnit.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 {
            for (int i = 0, size = futures.size(); i < size; i++)
                futures.get(i).cancel(true);
        }
    }

    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<Future<T>>(tasks.size());
        boolean done = false;
        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 ignore) {
                    } catch (ExecutionException ignore) {
                    }
                }
            }
            done = true;
            return futures;
        } finally {
            if (!done)
                for (int i = 0, size = futures.size(); i < size; i++)
                    futures.get(i).cancel(true);
        }
    }

    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
                                         long timeout, TimeUnit unit)
        throws InterruptedException {
        if (tasks == null)
            throw new NullPointerException();
        long nanos = unit.toNanos(timeout);
        ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
        boolean done = false;
        try {
            for (Callable<T> t : tasks)
                futures.add(newTaskFor(t));

            final long deadline = System.nanoTime() + nanos;
            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++) {
                execute((Runnable)futures.get(i));
                nanos = deadline - System.nanoTime();
                if (nanos <= 0L)
                    return futures;
            }

            for (int i = 0; i < size; i++) {
                Future<T> f = futures.get(i);
                if (!f.isDone()) {
                    if (nanos <= 0L)
                        return futures;
                    try {
                        f.get(nanos, TimeUnit.NANOSECONDS);
                    } catch (CancellationException ignore) {
                    } catch (ExecutionException ignore) {
                    } catch (TimeoutException toe) {
                        return futures;
                    }
                    nanos = deadline - System.nanoTime();
                }
            }
            done = true;
            return futures;
        } finally {
            if (!done)
                for (int i = 0, size = futures.size(); i < size; i++)
                    futures.get(i).cancel(true);
        }
    }

}
Revision:	1.45
Committed:	Thu Jul 18 01:36:08 2013 UTC (10 years, 10 months ago) by jsr166
Branch:	MAIN
Changes since 1.44:	+1 -0 lines
Log Message:	doclint warning fixes
#	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	import java.util.*;
9
10	/**
11	* Provides default implementations of {@link ExecutorService}
12	* execution methods. This class implements the {@code submit},
13	* {@code invokeAny} and {@code invokeAll} methods using a
14	* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
15	* to the {@link FutureTask} class provided in this package. For example,
16	* the implementation of {@code submit(Runnable)} creates an
17	* associated {@code RunnableFuture} that is executed and
18	* returned. Subclasses may override the {@code newTaskFor} methods
19	* to return {@code RunnableFuture} implementations other than
20	* {@code FutureTask}.
21	*
22	* <p><b>Extension example</b>. Here is a sketch of a class
23	* that customizes {@link ThreadPoolExecutor} to use
24	* a {@code CustomTask} class instead of the default {@code FutureTask}:
25	* <pre> {@code
26	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
27	*
28	* static class CustomTask<V> implements RunnableFuture<V> {...}
29	*
30	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
31	* return new CustomTask<V>(c);
32	* }
33	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
34	* return new CustomTask<V>(r, v);
35	* }
36	* // ... add constructors, etc.
37	* }}</pre>
38	*
39	* @since 1.5
40	* @author Doug Lea
41	*/
42	public abstract class AbstractExecutorService implements ExecutorService {
43
44	/**
45	* Returns a {@code RunnableFuture} for the given runnable and default
46	* value.
47	*
48	* @param runnable the runnable task being wrapped
49	* @param value the default value for the returned future
50	* @param <T> the type of the returned future's value
51	* @return a {@code RunnableFuture} which, when run, will run the
52	* underlying runnable and which, as a {@code Future}, will yield
53	* the given value as its result and provide for cancellation of
54	* the underlying task
55	* @since 1.6
56	*/
57	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
58	return new FutureTask<T>(runnable, value);
59	}
60
61	/**
62	* Returns a {@code RunnableFuture} for the given callable task.
63	*
64	* @param callable the callable task being wrapped
65	* @return a {@code RunnableFuture} which, when run, will call the
66	* underlying callable and which, as a {@code Future}, will yield
67	* the callable's result as its result and provide for
68	* cancellation of the underlying task
69	* @since 1.6
70	*/
71	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
72	return new FutureTask<T>(callable);
73	}
74
75	/**
76	* @throws RejectedExecutionException {@inheritDoc}
77	* @throws NullPointerException {@inheritDoc}
78	*/
79	public Future<?> submit(Runnable task) {
80	if (task == null) throw new NullPointerException();
81	RunnableFuture<Void> ftask = newTaskFor(task, null);
82	execute(ftask);
83	return ftask;
84	}
85
86	/**
87	* @throws RejectedExecutionException {@inheritDoc}
88	* @throws NullPointerException {@inheritDoc}
89	*/
90	public <T> Future<T> submit(Runnable task, T result) {
91	if (task == null) throw new NullPointerException();
92	RunnableFuture<T> ftask = newTaskFor(task, result);
93	execute(ftask);
94	return ftask;
95	}
96
97	/**
98	* @throws RejectedExecutionException {@inheritDoc}
99	* @throws NullPointerException {@inheritDoc}
100	*/
101	public <T> Future<T> submit(Callable<T> task) {
102	if (task == null) throw new NullPointerException();
103	RunnableFuture<T> ftask = newTaskFor(task);
104	execute(ftask);
105	return ftask;
106	}
107
108	/**
109	* the main mechanics of invokeAny.
110	*/
111	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
112	boolean timed, long nanos)
113	throws InterruptedException, ExecutionException, TimeoutException {
114	if (tasks == null)
115	throw new NullPointerException();
116	int ntasks = tasks.size();
117	if (ntasks == 0)
118	throw new IllegalArgumentException();
119	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(ntasks);
120	ExecutorCompletionService<T> ecs =
121	new ExecutorCompletionService<T>(this);
122
123	// For efficiency, especially in executors with limited
124	// parallelism, check to see if previously submitted tasks are
125	// done before submitting more of them. This interleaving
126	// plus the exception mechanics account for messiness of main
127	// loop.
128
129	try {
130	// Record exceptions so that if we fail to obtain any
131	// result, we can throw the last exception we got.
132	ExecutionException ee = null;
133	final long deadline = timed ? System.nanoTime() + nanos : 0L;
134	Iterator<? extends Callable<T>> it = tasks.iterator();
135
136	// Start one task for sure; the rest incrementally
137	futures.add(ecs.submit(it.next()));
138	--ntasks;
139	int active = 1;
140
141	for (;;) {
142	Future<T> f = ecs.poll();
143	if (f == null) {
144	if (ntasks > 0) {
145	--ntasks;
146	futures.add(ecs.submit(it.next()));
147	++active;
148	}
149	else if (active == 0)
150	break;
151	else if (timed) {
152	f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
153	if (f == null)
154	throw new TimeoutException();
155	nanos = deadline - System.nanoTime();
156	}
157	else
158	f = ecs.take();
159	}
160	if (f != null) {
161	--active;
162	try {
163	return f.get();
164	} catch (ExecutionException eex) {
165	ee = eex;
166	} catch (RuntimeException rex) {
167	ee = new ExecutionException(rex);
168	}
169	}
170	}
171
172	if (ee == null)
173	ee = new ExecutionException();
174	throw ee;
175
176	} finally {
177	for (int i = 0, size = futures.size(); i < size; i++)
178	futures.get(i).cancel(true);
179	}
180	}
181
182	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
183	throws InterruptedException, ExecutionException {
184	try {
185	return doInvokeAny(tasks, false, 0);
186	} catch (TimeoutException cannotHappen) {
187	assert false;
188	return null;
189	}
190	}
191
192	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
193	long timeout, TimeUnit unit)
194	throws InterruptedException, ExecutionException, TimeoutException {
195	return doInvokeAny(tasks, true, unit.toNanos(timeout));
196	}
197
198	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
199	throws InterruptedException {
200	if (tasks == null)
201	throw new NullPointerException();
202	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
203	boolean done = false;
204	try {
205	for (Callable<T> t : tasks) {
206	RunnableFuture<T> f = newTaskFor(t);
207	futures.add(f);
208	execute(f);
209	}
210	for (int i = 0, size = futures.size(); i < size; i++) {
211	Future<T> f = futures.get(i);
212	if (!f.isDone()) {
213	try {
214	f.get();
215	} catch (CancellationException ignore) {
216	} catch (ExecutionException ignore) {
217	}
218	}
219	}
220	done = true;
221	return futures;
222	} finally {
223	if (!done)
224	for (int i = 0, size = futures.size(); i < size; i++)
225	futures.get(i).cancel(true);
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	long nanos = unit.toNanos(timeout);
235	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
236	boolean done = false;
237	try {
238	for (Callable<T> t : tasks)
239	futures.add(newTaskFor(t));
240
241	final long deadline = System.nanoTime() + nanos;
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	execute((Runnable)futures.get(i));
248	nanos = deadline - System.nanoTime();
249	if (nanos <= 0L)
250	return futures;
251	}
252
253	for (int i = 0; i < size; i++) {
254	Future<T> f = futures.get(i);
255	if (!f.isDone()) {
256	if (nanos <= 0L)
257	return futures;
258	try {
259	f.get(nanos, TimeUnit.NANOSECONDS);
260	} catch (CancellationException ignore) {
261	} catch (ExecutionException ignore) {
262	} catch (TimeoutException toe) {
263	return futures;
264	}
265	nanos = deadline - System.nanoTime();
266	}
267	}
268	done = true;
269	return futures;
270	} finally {
271	if (!done)
272	for (int i = 0, size = futures.size(); i < size; i++)
273	futures.get(i).cancel(true);
274	}
275	}
276
277	}