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 <tt>submit</tt>,
 * <tt>invokeAny</tt> and <tt>invokeAll</tt> methods using a
 * {@link RunnableFuture} returned by <tt>newTaskFor</tt>, which defaults
 * to the {@link FutureTask} class provided in this package.  For example,
 * the implementation of <tt>submit(Runnable)</tt> creates an
 * associated <tt>RunnableFuture</tt> that is executed and
 * returned. Subclasses may override the <tt>newTaskFor</tt> methods
 * to return <tt>RunnableFuture</tt> implementations other than
 * <tt>FutureTask</tt>.
 *
 * <p> <b>Extension example</b>. Here is a sketch of a class
 * that customizes {@link ThreadPoolExecutor} to use
 * a <tt>CustomTask</tt> class instead of the default <tt>FutureTask</tt>:
 *  <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 <tt>RunnableFuture</tt> for the given runnable and default
     * value.
     *
     * @param runnable the runnable task being wrapped
     * @param value the default value for the returned future
     * @return a <tt>RunnableFuture</tt> which when run will run the
     * underlying runnable and which, as a <tt>Future</tt>, 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 <tt>RunnableFuture</tt> for the given callable task.
     *
     * @param callable the callable task being wrapped
     * @return a <tt>RunnableFuture</tt> which when run will call the
     * underlying callable and which, as a <tt>Future</tt>, 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();
        List<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 (Future<T> f : futures)
                f.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();
        List<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 (Future<T> f : futures) {
                if (!f.isDone()) {
                    try {
                        f.get();
                    } catch (CancellationException ignore) {
                    } catch (ExecutionException ignore) {
                    }
                }
            }
            done = true;
            return futures;
        } finally {
            if (!done)
                for (Future<T> f : futures)
                    f.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);
        List<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;

            // Interleave time checks and calls to execute in case
            // executor doesn't have any/much parallelism.
            Iterator<Future<T>> it = futures.iterator();
            while (it.hasNext()) {
                execute((Runnable)(it.next()));
                nanos = deadline - System.nanoTime();
                if (nanos <= 0L)
                    return futures;
            }

            for (Future<T> f : futures) {
                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 (Future<T> f : futures)
                    f.cancel(true);
        }
    }

}
Revision:	1.38
Committed:	Mon Dec 19 20:05:42 2011 UTC (12 years, 5 months ago) by jsr166
Branch:	MAIN
Changes since 1.37:	+1 -1 lines
Log Message:	remove redundant NullPointerException checks
#	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	dl	1.3	import java.util.*;
9	tim	1.1
10			/**
11	jsr166	1.24	* Provides default implementations of {@link ExecutorService}
12	dl	1.12	* execution methods. This class implements the <tt>submit</tt>,
13	peierls	1.21	* <tt>invokeAny</tt> and <tt>invokeAll</tt> methods using a
14			* {@link RunnableFuture} returned by <tt>newTaskFor</tt>, which defaults
15			* to the {@link FutureTask} class provided in this package. For example,
16	dl	1.18	* the implementation of <tt>submit(Runnable)</tt> creates an
17	peierls	1.21	* associated <tt>RunnableFuture</tt> that is executed and
18			* returned. Subclasses may override the <tt>newTaskFor</tt> methods
19	jsr166	1.24	* to return <tt>RunnableFuture</tt> implementations other than
20	peierls	1.21	* <tt>FutureTask</tt>.
21	tim	1.1	*
22	dl	1.22	* <p> <b>Extension example</b>. Here is a sketch of a class
23			* that customizes {@link ThreadPoolExecutor} to use
24			* a <tt>CustomTask</tt> class instead of the default <tt>FutureTask</tt>:
25	jsr166	1.32	* <pre> {@code
26	dl	1.22	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
27			*
28	jsr166	1.32	* static class CustomTask<V> implements RunnableFuture<V> {...}
29	dl	1.22	*
30	jsr166	1.32	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
31			* return new CustomTask<V>(c);
32	jsr166	1.25	* }
33	jsr166	1.32	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
34			* return new CustomTask<V>(r, v);
35	jsr166	1.25	* }
36			* // ... add constructors, etc.
37	jsr166	1.32	* }}</pre>
38			*
39	tim	1.1	* @since 1.5
40			* @author Doug Lea
41			*/
42			public abstract class AbstractExecutorService implements ExecutorService {
43
44	peierls	1.21	/**
45			* Returns a <tt>RunnableFuture</tt> for the given runnable and default
46			* value.
47	jsr166	1.24	*
48	peierls	1.21	* @param runnable the runnable task being wrapped
49			* @param value the default value for the returned future
50	dl	1.22	* @return a <tt>RunnableFuture</tt> which when run will run the
51			* underlying runnable and which, as a <tt>Future</tt>, will yield
52			* the given value as its result and provide for cancellation of
53			* the underlying task.
54			* @since 1.6
55	peierls	1.21	*/
56			protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
57			return new FutureTask<T>(runnable, value);
58			}
59
60			/**
61			* Returns a <tt>RunnableFuture</tt> for the given callable task.
62	jsr166	1.24	*
63	peierls	1.21	* @param callable the callable task being wrapped
64	dl	1.22	* @return a <tt>RunnableFuture</tt> which when run will call the
65			* underlying callable and which, as a <tt>Future</tt>, will yield
66			* the callable's result as its result and provide for
67			* cancellation of the underlying task.
68			* @since 1.6
69	peierls	1.21	*/
70			protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
71			return new FutureTask<T>(callable);
72			}
73
74	jsr166	1.30	/**
75			* @throws RejectedExecutionException {@inheritDoc}
76			* @throws NullPointerException {@inheritDoc}
77			*/
78	dl	1.11	public Future<?> submit(Runnable task) {
79	dl	1.13	if (task == null) throw new NullPointerException();
80	jsr166	1.33	RunnableFuture<Void> ftask = newTaskFor(task, null);
81	tim	1.1	execute(ftask);
82			return ftask;
83			}
84
85	jsr166	1.30	/**
86			* @throws RejectedExecutionException {@inheritDoc}
87			* @throws NullPointerException {@inheritDoc}
88			*/
89	dl	1.13	public <T> Future<T> submit(Runnable task, T result) {
90			if (task == null) throw new NullPointerException();
91	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task, result);
92	dl	1.13	execute(ftask);
93			return ftask;
94			}
95
96	jsr166	1.30	/**
97			* @throws RejectedExecutionException {@inheritDoc}
98			* @throws NullPointerException {@inheritDoc}
99			*/
100	tim	1.1	public <T> Future<T> submit(Callable<T> task) {
101	dl	1.13	if (task == null) throw new NullPointerException();
102	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task);
103	tim	1.1	execute(ftask);
104			return ftask;
105			}
106
107	dl	1.15	/**
108			* the main mechanics of invokeAny.
109			*/
110	jsr166	1.26	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
111	jsr166	1.36	boolean timed, long nanos)
112	dl	1.15	throws InterruptedException, ExecutionException, TimeoutException {
113	dl	1.3	if (tasks == null)
114			throw new NullPointerException();
115	dl	1.15	int ntasks = tasks.size();
116			if (ntasks == 0)
117	dl	1.7	throw new IllegalArgumentException();
118	dl	1.15	List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
119	jsr166	1.20	ExecutorCompletionService<T> ecs =
120	dl	1.7	new ExecutorCompletionService<T>(this);
121	dl	1.15
122			// For efficiency, especially in executors with limited
123			// parallelism, check to see if previously submitted tasks are
124	dl	1.18	// done before submitting more of them. This interleaving
125	dl	1.15	// plus the exception mechanics account for messiness of main
126	dl	1.18	// loop.
127	dl	1.15
128	dl	1.3	try {
129	dl	1.15	// Record exceptions so that if we fail to obtain any
130			// result, we can throw the last exception we got.
131	dl	1.7	ExecutionException ee = null;
132	jsr166	1.37	final long deadline = timed ? System.nanoTime() + nanos : 0L;
133	jsr166	1.26	Iterator<? extends Callable<T>> it = tasks.iterator();
134	dl	1.15
135			// Start one task for sure; the rest incrementally
136			futures.add(ecs.submit(it.next()));
137			--ntasks;
138			int active = 1;
139
140			for (;;) {
141	jsr166	1.20	Future<T> f = ecs.poll();
142	dl	1.15	if (f == null) {
143			if (ntasks > 0) {
144			--ntasks;
145			futures.add(ecs.submit(it.next()));
146			++active;
147			}
148	jsr166	1.20	else if (active == 0)
149	dl	1.15	break;
150			else if (timed) {
151			f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
152			if (f == null)
153			throw new TimeoutException();
154	jsr166	1.37	nanos = deadline - System.nanoTime();
155	dl	1.15	}
156	jsr166	1.20	else
157	dl	1.15	f = ecs.take();
158			}
159			if (f != null) {
160			--active;
161			try {
162			return f.get();
163	jsr166	1.19	} catch (ExecutionException eex) {
164	dl	1.15	ee = eex;
165	jsr166	1.19	} catch (RuntimeException rex) {
166	dl	1.15	ee = new ExecutionException(rex);
167			}
168	dl	1.7	}
169	jsr166	1.20	}
170	dl	1.15
171			if (ee == null)
172			ee = new ExecutionException();
173			throw ee;
174
175	dl	1.3	} finally {
176	jsr166	1.20	for (Future<T> f : futures)
177	dl	1.4	f.cancel(true);
178	dl	1.3	}
179			}
180
181	jsr166	1.26	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
182	dl	1.15	throws InterruptedException, ExecutionException {
183			try {
184			return doInvokeAny(tasks, false, 0);
185			} catch (TimeoutException cannotHappen) {
186			assert false;
187			return null;
188			}
189			}
190
191	jsr166	1.26	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
192	jsr166	1.20	long timeout, TimeUnit unit)
193	dl	1.7	throws InterruptedException, ExecutionException, TimeoutException {
194	dl	1.15	return doInvokeAny(tasks, true, unit.toNanos(timeout));
195	dl	1.3	}
196
197	jsr166	1.26	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
198	dl	1.3	throws InterruptedException {
199			if (tasks == null)
200			throw new NullPointerException();
201	dl	1.6	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
202			boolean done = false;
203	dl	1.3	try {
204			for (Callable<T> t : tasks) {
205	peierls	1.21	RunnableFuture<T> f = newTaskFor(t);
206	dl	1.3	futures.add(f);
207			execute(f);
208			}
209	dl	1.6	for (Future<T> f : futures) {
210			if (!f.isDone()) {
211	jsr166	1.20	try {
212			f.get();
213	jsr166	1.19	} catch (CancellationException ignore) {
214			} catch (ExecutionException ignore) {
215	dl	1.6	}
216			}
217			}
218			done = true;
219	dl	1.3	return futures;
220			} finally {
221	dl	1.6	if (!done)
222	jsr166	1.20	for (Future<T> f : futures)
223	dl	1.4	f.cancel(true);
224	dl	1.3	}
225			}
226
227	jsr166	1.26	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
228	jsr166	1.20	long timeout, TimeUnit unit)
229	dl	1.3	throws InterruptedException {
230	jsr166	1.38	if (tasks == null)
231	dl	1.3	throw new NullPointerException();
232			long nanos = unit.toNanos(timeout);
233	dl	1.6	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
234			boolean done = false;
235	dl	1.3	try {
236	jsr166	1.20	for (Callable<T> t : tasks)
237	peierls	1.21	futures.add(newTaskFor(t));
238	dl	1.16
239	jsr166	1.37	final long deadline = System.nanoTime() + nanos;
240	dl	1.16
241			// Interleave time checks and calls to execute in case
242			// executor doesn't have any/much parallelism.
243			Iterator<Future<T>> it = futures.iterator();
244			while (it.hasNext()) {
245			execute((Runnable)(it.next()));
246	jsr166	1.37	nanos = deadline - System.nanoTime();
247			if (nanos <= 0L)
248	jsr166	1.20	return futures;
249	dl	1.3	}
250	dl	1.16
251	dl	1.6	for (Future<T> f : futures) {
252			if (!f.isDone()) {
253	jsr166	1.37	if (nanos <= 0L)
254	jsr166	1.20	return futures;
255			try {
256			f.get(nanos, TimeUnit.NANOSECONDS);
257	jsr166	1.19	} catch (CancellationException ignore) {
258			} catch (ExecutionException ignore) {
259			} catch (TimeoutException toe) {
260	dl	1.6	return futures;
261			}
262	jsr166	1.37	nanos = deadline - System.nanoTime();
263	dl	1.6	}
264			}
265			done = true;
266	dl	1.3	return futures;
267			} finally {
268	dl	1.6	if (!done)
269	jsr166	1.20	for (Future<T> f : futures)
270	dl	1.4	f.cancel(true);
271	dl	1.3	}
272			}
273
274	tim	1.1	}