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
#	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	import java.util.*;
9
10	/**
11	* Provides default implementations of {@link ExecutorService}
12	* execution methods. This class implements the <tt>submit</tt>,
13	* <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	* the implementation of <tt>submit(Runnable)</tt> creates an
17	* associated <tt>RunnableFuture</tt> that is executed and
18	* returned. Subclasses may override the <tt>newTaskFor</tt> methods
19	* to return <tt>RunnableFuture</tt> implementations other than
20	* <tt>FutureTask</tt>.
21	*
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	* <pre> {@code
26	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
27	*
28	* static class CustomTask<V> implements RunnableFuture<V> {...}
29	*
30	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
31	* return new CustomTask<V>(c);
32	* }
33	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
34	* return new CustomTask<V>(r, v);
35	* }
36	* // ... add constructors, etc.
37	* }}</pre>
38	*
39	* @since 1.5
40	* @author Doug Lea
41	*/
42	public abstract class AbstractExecutorService implements ExecutorService {
43
44	/**
45	* Returns a <tt>RunnableFuture</tt> for the given runnable and default
46	* value.
47	*
48	* @param runnable the runnable task being wrapped
49	* @param value the default value for the returned future
50	* @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	*/
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	*
63	* @param callable the callable task being wrapped
64	* @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	*/
70	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
71	return new FutureTask<T>(callable);
72	}
73
74	/**
75	* @throws RejectedExecutionException {@inheritDoc}
76	* @throws NullPointerException {@inheritDoc}
77	*/
78	public Future<?> submit(Runnable task) {
79	if (task == null) throw new NullPointerException();
80	RunnableFuture<Void> ftask = newTaskFor(task, null);
81	execute(ftask);
82	return ftask;
83	}
84
85	/**
86	* @throws RejectedExecutionException {@inheritDoc}
87	* @throws NullPointerException {@inheritDoc}
88	*/
89	public <T> Future<T> submit(Runnable task, T result) {
90	if (task == null) throw new NullPointerException();
91	RunnableFuture<T> ftask = newTaskFor(task, result);
92	execute(ftask);
93	return ftask;
94	}
95
96	/**
97	* @throws RejectedExecutionException {@inheritDoc}
98	* @throws NullPointerException {@inheritDoc}
99	*/
100	public <T> Future<T> submit(Callable<T> task) {
101	if (task == null) throw new NullPointerException();
102	RunnableFuture<T> ftask = newTaskFor(task);
103	execute(ftask);
104	return ftask;
105	}
106
107	/**
108	* the main mechanics of invokeAny.
109	*/
110	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
111	boolean timed, long nanos)
112	throws InterruptedException, ExecutionException, TimeoutException {
113	if (tasks == null)
114	throw new NullPointerException();
115	int ntasks = tasks.size();
116	if (ntasks == 0)
117	throw new IllegalArgumentException();
118	List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
119	ExecutorCompletionService<T> ecs =
120	new ExecutorCompletionService<T>(this);
121
122	// For efficiency, especially in executors with limited
123	// parallelism, check to see if previously submitted tasks are
124	// done before submitting more of them. This interleaving
125	// plus the exception mechanics account for messiness of main
126	// loop.
127
128	try {
129	// Record exceptions so that if we fail to obtain any
130	// result, we can throw the last exception we got.
131	ExecutionException ee = null;
132	final long deadline = timed ? System.nanoTime() + nanos : 0L;
133	Iterator<? extends Callable<T>> it = tasks.iterator();
134
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	Future<T> f = ecs.poll();
142	if (f == null) {
143	if (ntasks > 0) {
144	--ntasks;
145	futures.add(ecs.submit(it.next()));
146	++active;
147	}
148	else if (active == 0)
149	break;
150	else if (timed) {
151	f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
152	if (f == null)
153	throw new TimeoutException();
154	nanos = deadline - System.nanoTime();
155	}
156	else
157	f = ecs.take();
158	}
159	if (f != null) {
160	--active;
161	try {
162	return f.get();
163	} catch (ExecutionException eex) {
164	ee = eex;
165	} catch (RuntimeException rex) {
166	ee = new ExecutionException(rex);
167	}
168	}
169	}
170
171	if (ee == null)
172	ee = new ExecutionException();
173	throw ee;
174
175	} finally {
176	for (Future<T> f : futures)
177	f.cancel(true);
178	}
179	}
180
181	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
182	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	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
192	long timeout, TimeUnit unit)
193	throws InterruptedException, ExecutionException, TimeoutException {
194	return doInvokeAny(tasks, true, unit.toNanos(timeout));
195	}
196
197	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
198	throws InterruptedException {
199	if (tasks == null)
200	throw new NullPointerException();
201	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
202	boolean done = false;
203	try {
204	for (Callable<T> t : tasks) {
205	RunnableFuture<T> f = newTaskFor(t);
206	futures.add(f);
207	execute(f);
208	}
209	for (Future<T> f : futures) {
210	if (!f.isDone()) {
211	try {
212	f.get();
213	} catch (CancellationException ignore) {
214	} catch (ExecutionException ignore) {
215	}
216	}
217	}
218	done = true;
219	return futures;
220	} finally {
221	if (!done)
222	for (Future<T> f : futures)
223	f.cancel(true);
224	}
225	}
226
227	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
228	long timeout, TimeUnit unit)
229	throws InterruptedException {
230	if (tasks == null)
231	throw new NullPointerException();
232	long nanos = unit.toNanos(timeout);
233	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
234	boolean done = false;
235	try {
236	for (Callable<T> t : tasks)
237	futures.add(newTaskFor(t));
238
239	final long deadline = System.nanoTime() + nanos;
240
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	nanos = deadline - System.nanoTime();
247	if (nanos <= 0L)
248	return futures;
249	}
250
251	for (Future<T> f : futures) {
252	if (!f.isDone()) {
253	if (nanos <= 0L)
254	return futures;
255	try {
256	f.get(nanos, TimeUnit.NANOSECONDS);
257	} catch (CancellationException ignore) {
258	} catch (ExecutionException ignore) {
259	} catch (TimeoutException toe) {
260	return futures;
261	}
262	nanos = deadline - System.nanoTime();
263	}
264	}
265	done = true;
266	return futures;
267	} finally {
268	if (!done)
269	for (Future<T> f : futures)
270	f.cancel(true);
271	}
272	}
273
274	}