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<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<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<Callable<T>> tasks)
        throws InterruptedException, ExecutionException {
        try {
            return doInvokeAny(tasks, false, 0);
        } catch (TimeoutException cannotHappen) {
            assert false;
            return null;
        }
    }

    public <T> T invokeAny(Collection<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<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<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:	1.24
Committed:	Sun Jun 12 00:35:38 2005 UTC (18 years, 11 months ago) by jsr166
Branch:	MAIN
Changes since 1.23:	+5 -3 lines
Log Message:	doc fixes
#	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
9	import java.util.*;
10
11	/**
12	* Provides default implementations of {@link ExecutorService}
13	* execution methods. This class implements the <tt>submit</tt>,
14	* <tt>invokeAny</tt> and <tt>invokeAll</tt> methods using a
15	* {@link RunnableFuture} returned by <tt>newTaskFor</tt>, which defaults
16	* to the {@link FutureTask} class provided in this package. For example,
17	* the implementation of <tt>submit(Runnable)</tt> creates an
18	* associated <tt>RunnableFuture</tt> that is executed and
19	* returned. Subclasses may override the <tt>newTaskFor</tt> methods
20	* to return <tt>RunnableFuture</tt> implementations other than
21	* <tt>FutureTask</tt>.
22	*
23	* <p> <b>Extension example</b>. Here is a sketch of a class
24	* that customizes {@link ThreadPoolExecutor} to use
25	* a <tt>CustomTask</tt> class instead of the default <tt>FutureTask</tt>:
26	* <pre>
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	* }
39	* </pre>
40	* @since 1.5
41	* @author Doug Lea
42	*/
43	public abstract class AbstractExecutorService implements ExecutorService {
44
45	/**
46	* Returns a <tt>RunnableFuture</tt> for the given runnable and default
47	* value.
48	*
49	* @param runnable the runnable task being wrapped
50	* @param value the default value for the returned future
51	* @return a <tt>RunnableFuture</tt> which when run will run the
52	* underlying runnable and which, as a <tt>Future</tt>, will yield
53	* the given value as its result and provide for cancellation of
54	* the underlying task.
55	* @since 1.6
56	*/
57	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
58	return new FutureTask<T>(runnable, value);
59	}
60
61	/**
62	* Returns a <tt>RunnableFuture</tt> for the given callable task.
63	*
64	* @param callable the callable task being wrapped
65	* @return a <tt>RunnableFuture</tt> which when run will call the
66	* underlying callable and which, as a <tt>Future</tt>, will yield
67	* the callable's result as its result and provide for
68	* cancellation of the underlying task.
69	* @since 1.6
70	*/
71	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
72	return new FutureTask<T>(callable);
73	}
74
75	public Future<?> submit(Runnable task) {
76	if (task == null) throw new NullPointerException();
77	RunnableFuture<Object> ftask = newTaskFor(task, null);
78	execute(ftask);
79	return ftask;
80	}
81
82	public <T> Future<T> submit(Runnable task, T result) {
83	if (task == null) throw new NullPointerException();
84	RunnableFuture<T> ftask = newTaskFor(task, result);
85	execute(ftask);
86	return ftask;
87	}
88
89	public <T> Future<T> submit(Callable<T> task) {
90	if (task == null) throw new NullPointerException();
91	RunnableFuture<T> ftask = newTaskFor(task);
92	execute(ftask);
93	return ftask;
94	}
95
96	/**
97	* the main mechanics of invokeAny.
98	*/
99	private <T> T doInvokeAny(Collection<Callable<T>> tasks,
100	boolean timed, long nanos)
101	throws InterruptedException, ExecutionException, TimeoutException {
102	if (tasks == null)
103	throw new NullPointerException();
104	int ntasks = tasks.size();
105	if (ntasks == 0)
106	throw new IllegalArgumentException();
107	List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
108	ExecutorCompletionService<T> ecs =
109	new ExecutorCompletionService<T>(this);
110
111	// For efficiency, especially in executors with limited
112	// parallelism, check to see if previously submitted tasks are
113	// done before submitting more of them. This interleaving
114	// plus the exception mechanics account for messiness of main
115	// loop.
116
117	try {
118	// Record exceptions so that if we fail to obtain any
119	// result, we can throw the last exception we got.
120	ExecutionException ee = null;
121	long lastTime = (timed)? System.nanoTime() : 0;
122	Iterator<Callable<T>> it = tasks.iterator();
123
124	// Start one task for sure; the rest incrementally
125	futures.add(ecs.submit(it.next()));
126	--ntasks;
127	int active = 1;
128
129	for (;;) {
130	Future<T> f = ecs.poll();
131	if (f == null) {
132	if (ntasks > 0) {
133	--ntasks;
134	futures.add(ecs.submit(it.next()));
135	++active;
136	}
137	else if (active == 0)
138	break;
139	else if (timed) {
140	f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
141	if (f == null)
142	throw new TimeoutException();
143	long now = System.nanoTime();
144	nanos -= now - lastTime;
145	lastTime = now;
146	}
147	else
148	f = ecs.take();
149	}
150	if (f != null) {
151	--active;
152	try {
153	return f.get();
154	} catch (InterruptedException ie) {
155	throw ie;
156	} catch (ExecutionException eex) {
157	ee = eex;
158	} catch (RuntimeException rex) {
159	ee = new ExecutionException(rex);
160	}
161	}
162	}
163
164	if (ee == null)
165	ee = new ExecutionException();
166	throw ee;
167
168	} finally {
169	for (Future<T> f : futures)
170	f.cancel(true);
171	}
172	}
173
174	public <T> T invokeAny(Collection<Callable<T>> tasks)
175	throws InterruptedException, ExecutionException {
176	try {
177	return doInvokeAny(tasks, false, 0);
178	} catch (TimeoutException cannotHappen) {
179	assert false;
180	return null;
181	}
182	}
183
184	public <T> T invokeAny(Collection<Callable<T>> tasks,
185	long timeout, TimeUnit unit)
186	throws InterruptedException, ExecutionException, TimeoutException {
187	return doInvokeAny(tasks, true, unit.toNanos(timeout));
188	}
189
190	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
191	throws InterruptedException {
192	if (tasks == null)
193	throw new NullPointerException();
194	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
195	boolean done = false;
196	try {
197	for (Callable<T> t : tasks) {
198	RunnableFuture<T> f = newTaskFor(t);
199	futures.add(f);
200	execute(f);
201	}
202	for (Future<T> f : futures) {
203	if (!f.isDone()) {
204	try {
205	f.get();
206	} catch (CancellationException ignore) {
207	} catch (ExecutionException ignore) {
208	}
209	}
210	}
211	done = true;
212	return futures;
213	} finally {
214	if (!done)
215	for (Future<T> f : futures)
216	f.cancel(true);
217	}
218	}
219
220	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
221	long timeout, TimeUnit unit)
222	throws InterruptedException {
223	if (tasks == null \|\| unit == null)
224	throw new NullPointerException();
225	long nanos = unit.toNanos(timeout);
226	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
227	boolean done = false;
228	try {
229	for (Callable<T> t : tasks)
230	futures.add(newTaskFor(t));
231
232	long lastTime = System.nanoTime();
233
234	// Interleave time checks and calls to execute in case
235	// executor doesn't have any/much parallelism.
236	Iterator<Future<T>> it = futures.iterator();
237	while (it.hasNext()) {
238	execute((Runnable)(it.next()));
239	long now = System.nanoTime();
240	nanos -= now - lastTime;
241	lastTime = now;
242	if (nanos <= 0)
243	return futures;
244	}
245
246	for (Future<T> f : futures) {
247	if (!f.isDone()) {
248	if (nanos <= 0)
249	return futures;
250	try {
251	f.get(nanos, TimeUnit.NANOSECONDS);
252	} catch (CancellationException ignore) {
253	} catch (ExecutionException ignore) {
254	} catch (TimeoutException toe) {
255	return futures;
256	}
257	long now = System.nanoTime();
258	nanos -= now - lastTime;
259	lastTime = now;
260	}
261	}
262	done = true;
263	return futures;
264	} finally {
265	if (!done)
266	for (Future<T> f : futures)
267	f.cancel(true);
268	}
269	}
270
271	}