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, 4 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
#	User	Rev	Content
1	dl	1.1	/*
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	jsr166	1.8
9	dl	1.1	import java.util.*;
10
11			/**
12			* Provides default implementations of {@link ExecutorService}
13	jsr166	1.2	* 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	dl	1.1	* to the {@link FutureTask} class provided in this package. For example,
17	jsr166	1.2	* 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	dl	1.1	*
23			* <p><b>Extension example</b>. Here is a sketch of a class
24			* that customizes {@link ThreadPoolExecutor} to use
25	jsr166	1.2	* a {@code CustomTask} class instead of the default {@code FutureTask}:
26	dl	1.1	* <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	jsr166	1.2	* Returns a {@code RunnableFuture} for the given runnable and default
47	dl	1.1	* value.
48			*
49			* @param runnable the runnable task being wrapped
50			* @param value the default value for the returned future
51	jsr166	1.7	* @param <T> the type of the given value
52	jsr166	1.6	* @return a {@code RunnableFuture} which, when run, will run the
53	jsr166	1.2	* underlying runnable and which, as a {@code Future}, will yield
54	dl	1.1	* the given value as its result and provide for cancellation of
55	jsr166	1.5	* the underlying task
56	dl	1.1	* @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	jsr166	1.2	* Returns a {@code RunnableFuture} for the given callable task.
64	dl	1.1	*
65			* @param callable the callable task being wrapped
66	jsr166	1.7	* @param <T> the type of the callable's result
67	jsr166	1.6	* @return a {@code RunnableFuture} which, when run, will call the
68	jsr166	1.2	* underlying callable and which, as a {@code Future}, will yield
69	dl	1.1	* the callable's result as its result and provide for
70	jsr166	1.5	* cancellation of the underlying task
71	dl	1.1	* @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	jsr166	1.4	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(ntasks);
122	dl	1.1	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	jsr166	1.4	for (int i = 0, size = futures.size(); i < size; i++)
180			futures.get(i).cancel(true);
181	dl	1.1	}
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	jsr166	1.4	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
205	dl	1.1	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	jsr166	1.4	for (int i = 0, size = futures.size(); i < size; i++) {
213			Future<T> f = futures.get(i);
214	dl	1.1	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	jsr166	1.4	for (int i = 0, size = futures.size(); i < size; i++)
227			futures.get(i).cancel(true);
228	dl	1.1	}
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	jsr166	1.4	ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
238	dl	1.1	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	jsr166	1.4	final int size = futures.size();
245	dl	1.1
246			// Interleave time checks and calls to execute in case
247			// executor doesn't have any/much parallelism.
248	jsr166	1.4	for (int i = 0; i < size; i++) {
249			execute((Runnable)futures.get(i));
250	dl	1.1	nanos = deadline - System.nanoTime();
251			if (nanos <= 0L)
252			return futures;
253			}
254
255	jsr166	1.4	for (int i = 0; i < size; i++) {
256			Future<T> f = futures.get(i);
257	dl	1.1	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	jsr166	1.4	for (int i = 0, size = futures.size(); i < size; i++)
275			futures.get(i).cancel(true);
276	dl	1.1	}
277			}
278
279			}