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/licenses/publicdomain
 */

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>
 * public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
 *
 *   static class CustomTask&lt;V&gt; implements RunnableFuture&lt;V&gt; {...}
 *
 *   protected &lt;V&gt; RunnableFuture&lt;V&gt; newTaskFor(Callable&lt;V&gt; c) {
 *       return new CustomTask&lt;V&gt;(c);
 *   }
 *   protected &lt;V&gt; RunnableFuture&lt;V&gt; newTaskFor(Runnable r, V v) {
 *       return new CustomTask&lt;V&gt;(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);
    }

    public Future<?> submit(Runnable task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<Object> ftask = newTaskFor(task, null);
        execute(ftask);
        return ftask;
    }

    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;
    }

    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;
            long lastTime = (timed)? System.nanoTime() : 0;
            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();
                        long now = System.nanoTime();
                        nanos -= now - lastTime;
                        lastTime = now;
                    }
                    else
                        f = ecs.take();
                }
                if (f != null) {
                    --active;
                    try {
                        return f.get();
                    } catch (InterruptedException ie) {
                        throw ie;
                    } 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 || unit == 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));

            long lastTime = System.nanoTime();

            // 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()));
                long now = System.nanoTime();
                nanos -= now - lastTime;
                lastTime = now;
                if (nanos <= 0)
                    return futures;
            }

            for (Future<T> f : futures) {
                if (!f.isDone()) {
                    if (nanos <= 0)
                        return futures;
                    try {
                        f.get(nanos, TimeUnit.NANOSECONDS);
                    } catch (CancellationException ignore) {
                    } catch (ExecutionException ignore) {
                    } catch (TimeoutException toe) {
                        return futures;
                    }
                    long now = System.nanoTime();
                    nanos -= now - lastTime;
                    lastTime = now;
                }
            }
            done = true;
            return futures;
        } finally {
            if (!done)
                for (Future<T> f : futures)
                    f.cancel(true);
        }
    }

}
Revision:	1.28
Committed:	Sun Jun 25 17:42:22 2006 UTC (17 years, 11 months ago) by jsr166
Branch:	MAIN
Changes since 1.27:	+1 -1 lines
Log Message:	whitespace
#	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/licenses/publicdomain
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>
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	* }
38	* </pre>
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	public Future<?> submit(Runnable task) {
75	if (task == null) throw new NullPointerException();
76	RunnableFuture<Object> ftask = newTaskFor(task, null);
77	execute(ftask);
78	return ftask;
79	}
80
81	public <T> Future<T> submit(Runnable task, T result) {
82	if (task == null) throw new NullPointerException();
83	RunnableFuture<T> ftask = newTaskFor(task, result);
84	execute(ftask);
85	return ftask;
86	}
87
88	public <T> Future<T> submit(Callable<T> task) {
89	if (task == null) throw new NullPointerException();
90	RunnableFuture<T> ftask = newTaskFor(task);
91	execute(ftask);
92	return ftask;
93	}
94
95	/**
96	* the main mechanics of invokeAny.
97	*/
98	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
99	boolean timed, long nanos)
100	throws InterruptedException, ExecutionException, TimeoutException {
101	if (tasks == null)
102	throw new NullPointerException();
103	int ntasks = tasks.size();
104	if (ntasks == 0)
105	throw new IllegalArgumentException();
106	List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
107	ExecutorCompletionService<T> ecs =
108	new ExecutorCompletionService<T>(this);
109
110	// For efficiency, especially in executors with limited
111	// parallelism, check to see if previously submitted tasks are
112	// done before submitting more of them. This interleaving
113	// plus the exception mechanics account for messiness of main
114	// loop.
115
116	try {
117	// Record exceptions so that if we fail to obtain any
118	// result, we can throw the last exception we got.
119	ExecutionException ee = null;
120	long lastTime = (timed)? System.nanoTime() : 0;
121	Iterator<? extends Callable<T>> it = tasks.iterator();
122
123	// Start one task for sure; the rest incrementally
124	futures.add(ecs.submit(it.next()));
125	--ntasks;
126	int active = 1;
127
128	for (;;) {
129	Future<T> f = ecs.poll();
130	if (f == null) {
131	if (ntasks > 0) {
132	--ntasks;
133	futures.add(ecs.submit(it.next()));
134	++active;
135	}
136	else if (active == 0)
137	break;
138	else if (timed) {
139	f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
140	if (f == null)
141	throw new TimeoutException();
142	long now = System.nanoTime();
143	nanos -= now - lastTime;
144	lastTime = now;
145	}
146	else
147	f = ecs.take();
148	}
149	if (f != null) {
150	--active;
151	try {
152	return f.get();
153	} catch (InterruptedException ie) {
154	throw ie;
155	} catch (ExecutionException eex) {
156	ee = eex;
157	} catch (RuntimeException rex) {
158	ee = new ExecutionException(rex);
159	}
160	}
161	}
162
163	if (ee == null)
164	ee = new ExecutionException();
165	throw ee;
166
167	} finally {
168	for (Future<T> f : futures)
169	f.cancel(true);
170	}
171	}
172
173	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
174	throws InterruptedException, ExecutionException {
175	try {
176	return doInvokeAny(tasks, false, 0);
177	} catch (TimeoutException cannotHappen) {
178	assert false;
179	return null;
180	}
181	}
182
183	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
184	long timeout, TimeUnit unit)
185	throws InterruptedException, ExecutionException, TimeoutException {
186	return doInvokeAny(tasks, true, unit.toNanos(timeout));
187	}
188
189	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
190	throws InterruptedException {
191	if (tasks == null)
192	throw new NullPointerException();
193	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
194	boolean done = false;
195	try {
196	for (Callable<T> t : tasks) {
197	RunnableFuture<T> f = newTaskFor(t);
198	futures.add(f);
199	execute(f);
200	}
201	for (Future<T> f : futures) {
202	if (!f.isDone()) {
203	try {
204	f.get();
205	} catch (CancellationException ignore) {
206	} catch (ExecutionException ignore) {
207	}
208	}
209	}
210	done = true;
211	return futures;
212	} finally {
213	if (!done)
214	for (Future<T> f : futures)
215	f.cancel(true);
216	}
217	}
218
219	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
220	long timeout, TimeUnit unit)
221	throws InterruptedException {
222	if (tasks == null \|\| unit == null)
223	throw new NullPointerException();
224	long nanos = unit.toNanos(timeout);
225	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
226	boolean done = false;
227	try {
228	for (Callable<T> t : tasks)
229	futures.add(newTaskFor(t));
230
231	long lastTime = System.nanoTime();
232
233	// Interleave time checks and calls to execute in case
234	// executor doesn't have any/much parallelism.
235	Iterator<Future<T>> it = futures.iterator();
236	while (it.hasNext()) {
237	execute((Runnable)(it.next()));
238	long now = System.nanoTime();
239	nanos -= now - lastTime;
240	lastTime = now;
241	if (nanos <= 0)
242	return futures;
243	}
244
245	for (Future<T> f : futures) {
246	if (!f.isDone()) {
247	if (nanos <= 0)
248	return futures;
249	try {
250	f.get(nanos, TimeUnit.NANOSECONDS);
251	} catch (CancellationException ignore) {
252	} catch (ExecutionException ignore) {
253	} catch (TimeoutException toe) {
254	return futures;
255	}
256	long now = System.nanoTime();
257	nanos -= now - lastTime;
258	lastTime = now;
259	}
260	}
261	done = true;
262	return futures;
263	} finally {
264	if (!done)
265	for (Future<T> f : futures)
266	f.cancel(true);
267	}
268	}
269
270	}