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 ignore) {}
                    catch (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 ignore) {}
                    catch (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:	1.1
Committed:	Sat Mar 26 06:22:49 2016 UTC (8 years, 2 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Log Message:	fork jdk8 maintenance branch for source and jtreg tests
#	User	Rev	Content
1	jsr166	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
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 ignore) {}
220			catch (ExecutionException ignore) {}
221			}
222			}
223			return futures;
224			} catch (Throwable t) {
225			cancelAll(futures);
226			throw t;
227			}
228			}
229
230			public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
231			long timeout, TimeUnit unit)
232			throws InterruptedException {
233			if (tasks == null)
234			throw new NullPointerException();
235			final long nanos = unit.toNanos(timeout);
236			final long deadline = System.nanoTime() + nanos;
237			ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
238			int j = 0;
239			timedOut: try {
240			for (Callable<T> t : tasks)
241			futures.add(newTaskFor(t));
242
243			final int size = futures.size();
244
245			// Interleave time checks and calls to execute in case
246			// executor doesn't have any/much parallelism.
247			for (int i = 0; i < size; i++) {
248			if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
249			break timedOut;
250			execute((Runnable)futures.get(i));
251			}
252
253			for (; j < size; j++) {
254			Future<T> f = futures.get(j);
255			if (!f.isDone()) {
256			try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
257			catch (CancellationException ignore) {}
258			catch (ExecutionException ignore) {}
259			catch (TimeoutException timedOut) {
260			break timedOut;
261			}
262			}
263			}
264			return futures;
265			} catch (Throwable t) {
266			cancelAll(futures);
267			throw t;
268			}
269			// Timed out before all the tasks could be completed; cancel remaining
270			cancelAll(futures, j);
271			return futures;
272			}
273
274			private static <T> void cancelAll(ArrayList<Future<T>> futures) {
275			cancelAll(futures, 0);
276			}
277
278			/** Cancels all futures with index at least j. */
279			private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
280			for (int size = futures.size(); j < size; j++)
281			futures.get(j).cancel(true);
282			}
283			}