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 implementation 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 other <tt>RunnableFuture</tt> implementations 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; {...}
 *
 *    &lt;V&gt; protected RunnableFuture&lt;V&gt; newTaskFor(Callable&lt;V&gt; c) {
 *         return new CustomTask&lt;V&gt;(c);
 *     }
 *    &lt;V&gt; protected 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:	1.22
Committed:	Tue May 17 13:08:08 2005 UTC (19 years ago) by dl
Branch:	MAIN
Changes since 1.21:	+27 -6 lines
Log Message:	Add documentation; adjust STPE internal types
#	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 implementation 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 other <tt>RunnableFuture</tt> implementations 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	* <V> protected RunnableFuture<V> newTaskFor(Callable<V> c) {
32	* return new CustomTask<V>(c);
33	* }
34	* <V> protected 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	* @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	* @param callable the callable task being wrapped
63	* @return a <tt>RunnableFuture</tt> which when run will call the
64	* underlying callable and which, as a <tt>Future</tt>, will yield
65	* the callable's result as its result and provide for
66	* cancellation of the underlying task.
67	* @since 1.6
68	*/
69	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
70	return new FutureTask<T>(callable);
71	}
72
73	public Future<?> submit(Runnable task) {
74	if (task == null) throw new NullPointerException();
75	RunnableFuture<Object> ftask = newTaskFor(task, null);
76	execute(ftask);
77	return ftask;
78	}
79
80	public <T> Future<T> submit(Runnable task, T result) {
81	if (task == null) throw new NullPointerException();
82	RunnableFuture<T> ftask = newTaskFor(task, result);
83	execute(ftask);
84	return ftask;
85	}
86
87	public <T> Future<T> submit(Callable<T> task) {
88	if (task == null) throw new NullPointerException();
89	RunnableFuture<T> ftask = newTaskFor(task);
90	execute(ftask);
91	return ftask;
92	}
93
94	/**
95	* the main mechanics of invokeAny.
96	*/
97	private <T> T doInvokeAny(Collection<Callable<T>> tasks,
98	boolean timed, long nanos)
99	throws InterruptedException, ExecutionException, TimeoutException {
100	if (tasks == null)
101	throw new NullPointerException();
102	int ntasks = tasks.size();
103	if (ntasks == 0)
104	throw new IllegalArgumentException();
105	List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
106	ExecutorCompletionService<T> ecs =
107	new ExecutorCompletionService<T>(this);
108
109	// For efficiency, especially in executors with limited
110	// parallelism, check to see if previously submitted tasks are
111	// done before submitting more of them. This interleaving
112	// plus the exception mechanics account for messiness of main
113	// loop.
114
115	try {
116	// Record exceptions so that if we fail to obtain any
117	// result, we can throw the last exception we got.
118	ExecutionException ee = null;
119	long lastTime = (timed)? System.nanoTime() : 0;
120	Iterator<Callable<T>> it = tasks.iterator();
121
122	// Start one task for sure; the rest incrementally
123	futures.add(ecs.submit(it.next()));
124	--ntasks;
125	int active = 1;
126
127	for (;;) {
128	Future<T> f = ecs.poll();
129	if (f == null) {
130	if (ntasks > 0) {
131	--ntasks;
132	futures.add(ecs.submit(it.next()));
133	++active;
134	}
135	else if (active == 0)
136	break;
137	else if (timed) {
138	f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
139	if (f == null)
140	throw new TimeoutException();
141	long now = System.nanoTime();
142	nanos -= now - lastTime;
143	lastTime = now;
144	}
145	else
146	f = ecs.take();
147	}
148	if (f != null) {
149	--active;
150	try {
151	return f.get();
152	} catch (InterruptedException ie) {
153	throw ie;
154	} catch (ExecutionException eex) {
155	ee = eex;
156	} catch (RuntimeException rex) {
157	ee = new ExecutionException(rex);
158	}
159	}
160	}
161
162	if (ee == null)
163	ee = new ExecutionException();
164	throw ee;
165
166	} finally {
167	for (Future<T> f : futures)
168	f.cancel(true);
169	}
170	}
171
172	public <T> T invokeAny(Collection<Callable<T>> tasks)
173	throws InterruptedException, ExecutionException {
174	try {
175	return doInvokeAny(tasks, false, 0);
176	} catch (TimeoutException cannotHappen) {
177	assert false;
178	return null;
179	}
180	}
181
182	public <T> T invokeAny(Collection<Callable<T>> tasks,
183	long timeout, TimeUnit unit)
184	throws InterruptedException, ExecutionException, TimeoutException {
185	return doInvokeAny(tasks, true, unit.toNanos(timeout));
186	}
187
188	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
189	throws InterruptedException {
190	if (tasks == null)
191	throw new NullPointerException();
192	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
193	boolean done = false;
194	try {
195	for (Callable<T> t : tasks) {
196	RunnableFuture<T> f = newTaskFor(t);
197	futures.add(f);
198	execute(f);
199	}
200	for (Future<T> f : futures) {
201	if (!f.isDone()) {
202	try {
203	f.get();
204	} catch (CancellationException ignore) {
205	} catch (ExecutionException ignore) {
206	}
207	}
208	}
209	done = true;
210	return futures;
211	} finally {
212	if (!done)
213	for (Future<T> f : futures)
214	f.cancel(true);
215	}
216	}
217
218	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
219	long timeout, TimeUnit unit)
220	throws InterruptedException {
221	if (tasks == null \|\| unit == null)
222	throw new NullPointerException();
223	long nanos = unit.toNanos(timeout);
224	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
225	boolean done = false;
226	try {
227	for (Callable<T> t : tasks)
228	futures.add(newTaskFor(t));
229
230	long lastTime = System.nanoTime();
231
232	// Interleave time checks and calls to execute in case
233	// executor doesn't have any/much parallelism.
234	Iterator<Future<T>> it = futures.iterator();
235	while (it.hasNext()) {
236	execute((Runnable)(it.next()));
237	long now = System.nanoTime();
238	nanos -= now - lastTime;
239	lastTime = now;
240	if (nanos <= 0)
241	return futures;
242	}
243
244	for (Future<T> f : futures) {
245	if (!f.isDone()) {
246	if (nanos <= 0)
247	return futures;
248	try {
249	f.get(nanos, TimeUnit.NANOSECONDS);
250	} catch (CancellationException ignore) {
251	} catch (ExecutionException ignore) {
252	} catch (TimeoutException toe) {
253	return futures;
254	}
255	long now = System.nanoTime();
256	nanos -= now - lastTime;
257	lastTime = now;
258	}
259	}
260	done = true;
261	return futures;
262	} finally {
263	if (!done)
264	for (Future<T> f : futures)
265	f.cancel(true);
266	}
267	}
268
269	}