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 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<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:	1.8
Committed:	Sun Jan 18 20:17:32 2015 UTC (9 years, 3 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.7:	+1 -0 lines
Log Message:	exactly one blank line before and after package statements
#	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 java.util.*;
10
11	/**
12	* Provides default implementations of {@link ExecutorService}
13	* execution methods. This class implements the {@code submit},
14	* {@code invokeAny} and {@code invokeAll} methods using a
15	* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
16	* to the {@link FutureTask} class provided in this package. For example,
17	* the implementation of {@code submit(Runnable)} creates an
18	* associated {@code RunnableFuture} that is executed and
19	* returned. Subclasses may override the {@code newTaskFor} methods
20	* to return {@code RunnableFuture} implementations other than
21	* {@code FutureTask}.
22	*
23	* <p><b>Extension example</b>. Here is a sketch of a class
24	* that customizes {@link ThreadPoolExecutor} to use
25	* a {@code CustomTask} class instead of the default {@code FutureTask}:
26	* <pre> {@code
27	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
28	*
29	* static class CustomTask<V> implements RunnableFuture<V> {...}
30	*
31	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
32	* return new CustomTask<V>(c);
33	* }
34	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
35	* return new CustomTask<V>(r, v);
36	* }
37	* // ... add constructors, etc.
38	* }}</pre>
39	*
40	* @since 1.5
41	* @author Doug Lea
42	*/
43	public abstract class AbstractExecutorService implements ExecutorService {
44
45	/**
46	* Returns a {@code RunnableFuture} for the given runnable and default
47	* value.
48	*
49	* @param runnable the runnable task being wrapped
50	* @param value the default value for the returned future
51	* @param <T> the type of the given value
52	* @return a {@code RunnableFuture} which, when run, will run the
53	* underlying runnable and which, as a {@code Future}, will yield
54	* the given value as its result and provide for cancellation of
55	* the underlying task
56	* @since 1.6
57	*/
58	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
59	return new FutureTask<T>(runnable, value);
60	}
61
62	/**
63	* Returns a {@code RunnableFuture} for the given callable task.
64	*
65	* @param callable the callable task being wrapped
66	* @param <T> the type of the callable's result
67	* @return a {@code RunnableFuture} which, when run, will call the
68	* underlying callable and which, as a {@code Future}, will yield
69	* the callable's result as its result and provide for
70	* cancellation of the underlying task
71	* @since 1.6
72	*/
73	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
74	return new FutureTask<T>(callable);
75	}
76
77	/**
78	* @throws RejectedExecutionException {@inheritDoc}
79	* @throws NullPointerException {@inheritDoc}
80	*/
81	public Future<?> submit(Runnable task) {
82	if (task == null) throw new NullPointerException();
83	RunnableFuture<Void> ftask = newTaskFor(task, null);
84	execute(ftask);
85	return ftask;
86	}
87
88	/**
89	* @throws RejectedExecutionException {@inheritDoc}
90	* @throws NullPointerException {@inheritDoc}
91	*/
92	public <T> Future<T> submit(Runnable task, T result) {
93	if (task == null) throw new NullPointerException();
94	RunnableFuture<T> ftask = newTaskFor(task, result);
95	execute(ftask);
96	return ftask;
97	}
98
99	/**
100	* @throws RejectedExecutionException {@inheritDoc}
101	* @throws NullPointerException {@inheritDoc}
102	*/
103	public <T> Future<T> submit(Callable<T> task) {
104	if (task == null) throw new NullPointerException();
105	RunnableFuture<T> ftask = newTaskFor(task);
106	execute(ftask);
107	return ftask;
108	}
109
110	/**
111	* the main mechanics of invokeAny.
112	*/
113	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
114	boolean timed, long nanos)
115	throws InterruptedException, ExecutionException, TimeoutException {
116	if (tasks == null)
117	throw new NullPointerException();
118	int ntasks = tasks.size();
119	if (ntasks == 0)
120	throw new IllegalArgumentException();
121	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(ntasks);
122	ExecutorCompletionService<T> ecs =
123	new ExecutorCompletionService<T>(this);
124
125	// For efficiency, especially in executors with limited
126	// parallelism, check to see if previously submitted tasks are
127	// done before submitting more of them. This interleaving
128	// plus the exception mechanics account for messiness of main
129	// loop.
130
131	try {
132	// Record exceptions so that if we fail to obtain any
133	// result, we can throw the last exception we got.
134	ExecutionException ee = null;
135	final long deadline = timed ? System.nanoTime() + nanos : 0L;
136	Iterator<? extends Callable<T>> it = tasks.iterator();
137
138	// Start one task for sure; the rest incrementally
139	futures.add(ecs.submit(it.next()));
140	--ntasks;
141	int active = 1;
142
143	for (;;) {
144	Future<T> f = ecs.poll();
145	if (f == null) {
146	if (ntasks > 0) {
147	--ntasks;
148	futures.add(ecs.submit(it.next()));
149	++active;
150	}
151	else if (active == 0)
152	break;
153	else if (timed) {
154	f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
155	if (f == null)
156	throw new TimeoutException();
157	nanos = deadline - System.nanoTime();
158	}
159	else
160	f = ecs.take();
161	}
162	if (f != null) {
163	--active;
164	try {
165	return f.get();
166	} catch (ExecutionException eex) {
167	ee = eex;
168	} catch (RuntimeException rex) {
169	ee = new ExecutionException(rex);
170	}
171	}
172	}
173
174	if (ee == null)
175	ee = new ExecutionException();
176	throw ee;
177
178	} finally {
179	for (int i = 0, size = futures.size(); i < size; i++)
180	futures.get(i).cancel(true);
181	}
182	}
183
184	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
185	throws InterruptedException, ExecutionException {
186	try {
187	return doInvokeAny(tasks, false, 0);
188	} catch (TimeoutException cannotHappen) {
189	assert false;
190	return null;
191	}
192	}
193
194	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
195	long timeout, TimeUnit unit)
196	throws InterruptedException, ExecutionException, TimeoutException {
197	return doInvokeAny(tasks, true, unit.toNanos(timeout));
198	}
199
200	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
201	throws InterruptedException {
202	if (tasks == null)
203	throw new NullPointerException();
204	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
205	boolean done = false;
206	try {
207	for (Callable<T> t : tasks) {
208	RunnableFuture<T> f = newTaskFor(t);
209	futures.add(f);
210	execute(f);
211	}
212	for (int i = 0, size = futures.size(); i < size; i++) {
213	Future<T> f = futures.get(i);
214	if (!f.isDone()) {
215	try {
216	f.get();
217	} catch (CancellationException ignore) {
218	} catch (ExecutionException ignore) {
219	}
220	}
221	}
222	done = true;
223	return futures;
224	} finally {
225	if (!done)
226	for (int i = 0, size = futures.size(); i < size; i++)
227	futures.get(i).cancel(true);
228	}
229	}
230
231	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
232	long timeout, TimeUnit unit)
233	throws InterruptedException {
234	if (tasks == null)
235	throw new NullPointerException();
236	long nanos = unit.toNanos(timeout);
237	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
238	boolean done = false;
239	try {
240	for (Callable<T> t : tasks)
241	futures.add(newTaskFor(t));
242
243	final long deadline = System.nanoTime() + nanos;
244	final int size = futures.size();
245
246	// Interleave time checks and calls to execute in case
247	// executor doesn't have any/much parallelism.
248	for (int i = 0; i < size; i++) {
249	execute((Runnable)futures.get(i));
250	nanos = deadline - System.nanoTime();
251	if (nanos <= 0L)
252	return futures;
253	}
254
255	for (int i = 0; i < size; i++) {
256	Future<T> f = futures.get(i);
257	if (!f.isDone()) {
258	if (nanos <= 0L)
259	return futures;
260	try {
261	f.get(nanos, TimeUnit.NANOSECONDS);
262	} catch (CancellationException ignore) {
263	} catch (ExecutionException ignore) {
264	} catch (TimeoutException toe) {
265	return futures;
266	}
267	nanos = deadline - System.nanoTime();
268	}
269	}
270	done = true;
271	return futures;
272	} finally {
273	if (!done)
274	for (int i = 0, size = futures.size(); i < size; i++)
275	futures.get(i).cancel(true);
276	}
277	}
278
279	}