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.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, 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<>(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<>(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:	1.48
Committed:	Wed Dec 3 21:55:44 2014 UTC (9 years, 6 months ago) by jsr166
Branch:	MAIN
Changes since 1.47:	+5 -1 lines
Log Message:	never use wildcard imports
#	User	Rev	Content
1	tim	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.17	* Expert Group and released to the public domain, as explained at
4	jsr166	1.35	* http://creativecommons.org/publicdomain/zero/1.0/
5	tim	1.1	*/
6
7			package java.util.concurrent;
8	jsr166	1.48
9			import java.util.ArrayList;
10			import java.util.Collection;
11			import java.util.Iterator;
12			import java.util.List;
13	tim	1.1
14			/**
15	jsr166	1.24	* Provides default implementations of {@link ExecutorService}
16	jsr166	1.40	* execution methods. This class implements the {@code submit},
17			* {@code invokeAny} and {@code invokeAll} methods using a
18			* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
19	peierls	1.21	* to the {@link FutureTask} class provided in this package. For example,
20	jsr166	1.40	* the implementation of {@code submit(Runnable)} creates an
21			* associated {@code RunnableFuture} that is executed and
22			* returned. Subclasses may override the {@code newTaskFor} methods
23			* to return {@code RunnableFuture} implementations other than
24			* {@code FutureTask}.
25	tim	1.1	*
26	jsr166	1.39	* <p><b>Extension example</b>. Here is a sketch of a class
27	dl	1.22	* that customizes {@link ThreadPoolExecutor} to use
28	jsr166	1.40	* a {@code CustomTask} class instead of the default {@code FutureTask}:
29	jsr166	1.32	* <pre> {@code
30	dl	1.22	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
31			*
32	jsr166	1.32	* static class CustomTask<V> implements RunnableFuture<V> {...}
33	dl	1.22	*
34	jsr166	1.32	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
35			* return new CustomTask<V>(c);
36	jsr166	1.25	* }
37	jsr166	1.32	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
38			* return new CustomTask<V>(r, v);
39	jsr166	1.25	* }
40			* // ... add constructors, etc.
41	jsr166	1.32	* }}</pre>
42			*
43	tim	1.1	* @since 1.5
44			* @author Doug Lea
45			*/
46			public abstract class AbstractExecutorService implements ExecutorService {
47
48	peierls	1.21	/**
49	jsr166	1.40	* Returns a {@code RunnableFuture} for the given runnable and default
50	peierls	1.21	* value.
51	jsr166	1.24	*
52	peierls	1.21	* @param runnable the runnable task being wrapped
53			* @param value the default value for the returned future
54	jsr166	1.46	* @param <T> the type of the given value
55	jsr166	1.44	* @return a {@code RunnableFuture} which, when run, will run the
56	jsr166	1.40	* underlying runnable and which, as a {@code Future}, will yield
57	dl	1.22	* the given value as its result and provide for cancellation of
58	jsr166	1.43	* the underlying task
59	dl	1.22	* @since 1.6
60	peierls	1.21	*/
61			protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
62			return new FutureTask<T>(runnable, value);
63			}
64
65			/**
66	jsr166	1.40	* Returns a {@code RunnableFuture} for the given callable task.
67	jsr166	1.24	*
68	peierls	1.21	* @param callable the callable task being wrapped
69	jsr166	1.46	* @param <T> the type of the callable's result
70	jsr166	1.44	* @return a {@code RunnableFuture} which, when run, will call the
71	jsr166	1.40	* underlying callable and which, as a {@code Future}, will yield
72	dl	1.22	* the callable's result as its result and provide for
73	jsr166	1.43	* cancellation of the underlying task
74	dl	1.22	* @since 1.6
75	peierls	1.21	*/
76			protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
77			return new FutureTask<T>(callable);
78			}
79
80	jsr166	1.30	/**
81			* @throws RejectedExecutionException {@inheritDoc}
82			* @throws NullPointerException {@inheritDoc}
83			*/
84	dl	1.11	public Future<?> submit(Runnable task) {
85	dl	1.13	if (task == null) throw new NullPointerException();
86	jsr166	1.33	RunnableFuture<Void> ftask = newTaskFor(task, null);
87	tim	1.1	execute(ftask);
88			return ftask;
89			}
90
91	jsr166	1.30	/**
92			* @throws RejectedExecutionException {@inheritDoc}
93			* @throws NullPointerException {@inheritDoc}
94			*/
95	dl	1.13	public <T> Future<T> submit(Runnable task, T result) {
96			if (task == null) throw new NullPointerException();
97	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task, result);
98	dl	1.13	execute(ftask);
99			return ftask;
100			}
101
102	jsr166	1.30	/**
103			* @throws RejectedExecutionException {@inheritDoc}
104			* @throws NullPointerException {@inheritDoc}
105			*/
106	tim	1.1	public <T> Future<T> submit(Callable<T> task) {
107	dl	1.13	if (task == null) throw new NullPointerException();
108	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task);
109	tim	1.1	execute(ftask);
110			return ftask;
111			}
112
113	dl	1.15	/**
114			* the main mechanics of invokeAny.
115			*/
116	jsr166	1.26	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
117	jsr166	1.36	boolean timed, long nanos)
118	dl	1.15	throws InterruptedException, ExecutionException, TimeoutException {
119	dl	1.3	if (tasks == null)
120			throw new NullPointerException();
121	dl	1.15	int ntasks = tasks.size();
122			if (ntasks == 0)
123	dl	1.7	throw new IllegalArgumentException();
124	jsr166	1.47	ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
125	jsr166	1.20	ExecutorCompletionService<T> ecs =
126	dl	1.7	new ExecutorCompletionService<T>(this);
127	dl	1.15
128			// For efficiency, especially in executors with limited
129			// parallelism, check to see if previously submitted tasks are
130	dl	1.18	// done before submitting more of them. This interleaving
131	dl	1.15	// plus the exception mechanics account for messiness of main
132	dl	1.18	// loop.
133	dl	1.15
134	dl	1.3	try {
135	dl	1.15	// Record exceptions so that if we fail to obtain any
136			// result, we can throw the last exception we got.
137	dl	1.7	ExecutionException ee = null;
138	jsr166	1.37	final long deadline = timed ? System.nanoTime() + nanos : 0L;
139	jsr166	1.26	Iterator<? extends Callable<T>> it = tasks.iterator();
140	dl	1.15
141			// Start one task for sure; the rest incrementally
142			futures.add(ecs.submit(it.next()));
143			--ntasks;
144			int active = 1;
145
146			for (;;) {
147	jsr166	1.20	Future<T> f = ecs.poll();
148	dl	1.15	if (f == null) {
149			if (ntasks > 0) {
150			--ntasks;
151			futures.add(ecs.submit(it.next()));
152			++active;
153			}
154	jsr166	1.20	else if (active == 0)
155	dl	1.15	break;
156			else if (timed) {
157			f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
158			if (f == null)
159			throw new TimeoutException();
160	jsr166	1.37	nanos = deadline - System.nanoTime();
161	dl	1.15	}
162	jsr166	1.20	else
163	dl	1.15	f = ecs.take();
164			}
165			if (f != null) {
166			--active;
167			try {
168			return f.get();
169	jsr166	1.19	} catch (ExecutionException eex) {
170	dl	1.15	ee = eex;
171	jsr166	1.19	} catch (RuntimeException rex) {
172	dl	1.15	ee = new ExecutionException(rex);
173			}
174	dl	1.7	}
175	jsr166	1.20	}
176	dl	1.15
177			if (ee == null)
178			ee = new ExecutionException();
179			throw ee;
180
181	dl	1.3	} finally {
182	jsr166	1.42	for (int i = 0, size = futures.size(); i < size; i++)
183			futures.get(i).cancel(true);
184	dl	1.3	}
185			}
186
187	jsr166	1.26	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
188	dl	1.15	throws InterruptedException, ExecutionException {
189			try {
190			return doInvokeAny(tasks, false, 0);
191			} catch (TimeoutException cannotHappen) {
192			assert false;
193			return null;
194			}
195			}
196
197	jsr166	1.26	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
198	jsr166	1.20	long timeout, TimeUnit unit)
199	dl	1.7	throws InterruptedException, ExecutionException, TimeoutException {
200	dl	1.15	return doInvokeAny(tasks, true, unit.toNanos(timeout));
201	dl	1.3	}
202
203	jsr166	1.26	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
204	dl	1.3	throws InterruptedException {
205			if (tasks == null)
206			throw new NullPointerException();
207	jsr166	1.47	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
208	dl	1.6	boolean done = false;
209	dl	1.3	try {
210			for (Callable<T> t : tasks) {
211	peierls	1.21	RunnableFuture<T> f = newTaskFor(t);
212	dl	1.3	futures.add(f);
213			execute(f);
214			}
215	jsr166	1.42	for (int i = 0, size = futures.size(); i < size; i++) {
216			Future<T> f = futures.get(i);
217	dl	1.6	if (!f.isDone()) {
218	jsr166	1.20	try {
219			f.get();
220	jsr166	1.19	} catch (CancellationException ignore) {
221			} catch (ExecutionException ignore) {
222	dl	1.6	}
223			}
224			}
225			done = true;
226	dl	1.3	return futures;
227			} finally {
228	dl	1.6	if (!done)
229	jsr166	1.42	for (int i = 0, size = futures.size(); i < size; i++)
230			futures.get(i).cancel(true);
231	dl	1.3	}
232			}
233
234	jsr166	1.26	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
235	jsr166	1.20	long timeout, TimeUnit unit)
236	dl	1.3	throws InterruptedException {
237	jsr166	1.38	if (tasks == null)
238	dl	1.3	throw new NullPointerException();
239			long nanos = unit.toNanos(timeout);
240	jsr166	1.47	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
241	dl	1.6	boolean done = false;
242	dl	1.3	try {
243	jsr166	1.20	for (Callable<T> t : tasks)
244	peierls	1.21	futures.add(newTaskFor(t));
245	dl	1.16
246	jsr166	1.37	final long deadline = System.nanoTime() + nanos;
247	jsr166	1.42	final int size = futures.size();
248	dl	1.16
249			// Interleave time checks and calls to execute in case
250			// executor doesn't have any/much parallelism.
251	jsr166	1.42	for (int i = 0; i < size; i++) {
252			execute((Runnable)futures.get(i));
253	jsr166	1.37	nanos = deadline - System.nanoTime();
254			if (nanos <= 0L)
255	jsr166	1.20	return futures;
256	dl	1.3	}
257	dl	1.16
258	jsr166	1.42	for (int i = 0; i < size; i++) {
259			Future<T> f = futures.get(i);
260	dl	1.6	if (!f.isDone()) {
261	jsr166	1.37	if (nanos <= 0L)
262	jsr166	1.20	return futures;
263			try {
264			f.get(nanos, TimeUnit.NANOSECONDS);
265	jsr166	1.19	} catch (CancellationException ignore) {
266			} catch (ExecutionException ignore) {
267			} catch (TimeoutException toe) {
268	dl	1.6	return futures;
269			}
270	jsr166	1.37	nanos = deadline - System.nanoTime();
271	dl	1.6	}
272			}
273			done = true;
274	dl	1.3	return futures;
275			} finally {
276	dl	1.6	if (!done)
277	jsr166	1.42	for (int i = 0, size = futures.size(); i < size; i++)
278			futures.get(i).cancel(true);
279	dl	1.3	}
280			}
281
282	tim	1.1	}