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 (19 years ago) by jsr166
Branch:	MAIN
Changes since 1.23:	+5 -3 lines
Log Message:	doc fixes
#	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			* http://creativecommons.org/licenses/publicdomain
5	tim	1.1	*/
6
7			package java.util.concurrent;
8
9	dl	1.3	import java.util.*;
10	tim	1.1
11			/**
12	jsr166	1.24	* Provides default implementations of {@link ExecutorService}
13	dl	1.12	* execution methods. This class implements the <tt>submit</tt>,
14	peierls	1.21	* <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	dl	1.18	* the implementation of <tt>submit(Runnable)</tt> creates an
18	peierls	1.21	* associated <tt>RunnableFuture</tt> that is executed and
19			* returned. Subclasses may override the <tt>newTaskFor</tt> methods
20	jsr166	1.24	* to return <tt>RunnableFuture</tt> implementations other than
21	peierls	1.21	* <tt>FutureTask</tt>.
22	tim	1.1	*
23	dl	1.22	* <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	dl	1.23	* static class CustomTask<V> implements RunnableFuture<V> {...}
30	dl	1.22	*
31	dl	1.23	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
32	dl	1.22	* return new CustomTask<V>(c);
33			* }
34	dl	1.23	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
35	dl	1.22	* return new CustomTask<V>(r, v);
36	jsr166	1.24	* }
37	dl	1.22	* // ... add constructors, etc.
38			* }
39			* </pre>
40	tim	1.1	* @since 1.5
41			* @author Doug Lea
42			*/
43			public abstract class AbstractExecutorService implements ExecutorService {
44
45	peierls	1.21	/**
46			* Returns a <tt>RunnableFuture</tt> for the given runnable and default
47			* value.
48	jsr166	1.24	*
49	peierls	1.21	* @param runnable the runnable task being wrapped
50			* @param value the default value for the returned future
51	dl	1.22	* @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	peierls	1.21	*/
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	jsr166	1.24	*
64	peierls	1.21	* @param callable the callable task being wrapped
65	dl	1.22	* @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	peierls	1.21	*/
71			protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
72			return new FutureTask<T>(callable);
73			}
74
75	dl	1.11	public Future<?> submit(Runnable task) {
76	dl	1.13	if (task == null) throw new NullPointerException();
77	peierls	1.21	RunnableFuture<Object> ftask = newTaskFor(task, null);
78	tim	1.1	execute(ftask);
79			return ftask;
80			}
81
82	dl	1.13	public <T> Future<T> submit(Runnable task, T result) {
83			if (task == null) throw new NullPointerException();
84	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task, result);
85	dl	1.13	execute(ftask);
86			return ftask;
87			}
88
89	tim	1.1	public <T> Future<T> submit(Callable<T> task) {
90	dl	1.13	if (task == null) throw new NullPointerException();
91	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task);
92	tim	1.1	execute(ftask);
93			return ftask;
94			}
95
96	dl	1.15	/**
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	dl	1.3	if (tasks == null)
103			throw new NullPointerException();
104	dl	1.15	int ntasks = tasks.size();
105			if (ntasks == 0)
106	dl	1.7	throw new IllegalArgumentException();
107	dl	1.15	List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
108	jsr166	1.20	ExecutorCompletionService<T> ecs =
109	dl	1.7	new ExecutorCompletionService<T>(this);
110	dl	1.15
111			// For efficiency, especially in executors with limited
112			// parallelism, check to see if previously submitted tasks are
113	dl	1.18	// done before submitting more of them. This interleaving
114	dl	1.15	// plus the exception mechanics account for messiness of main
115	dl	1.18	// loop.
116	dl	1.15
117	dl	1.3	try {
118	dl	1.15	// Record exceptions so that if we fail to obtain any
119			// result, we can throw the last exception we got.
120	dl	1.7	ExecutionException ee = null;
121	dl	1.15	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	jsr166	1.20	Future<T> f = ecs.poll();
131	dl	1.15	if (f == null) {
132			if (ntasks > 0) {
133			--ntasks;
134			futures.add(ecs.submit(it.next()));
135			++active;
136			}
137	jsr166	1.20	else if (active == 0)
138	dl	1.15	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	jsr166	1.20	else
148	dl	1.15	f = ecs.take();
149			}
150			if (f != null) {
151			--active;
152			try {
153			return f.get();
154	jsr166	1.19	} catch (InterruptedException ie) {
155	dl	1.15	throw ie;
156	jsr166	1.19	} catch (ExecutionException eex) {
157	dl	1.15	ee = eex;
158	jsr166	1.19	} catch (RuntimeException rex) {
159	dl	1.15	ee = new ExecutionException(rex);
160			}
161	dl	1.7	}
162	jsr166	1.20	}
163	dl	1.15
164			if (ee == null)
165			ee = new ExecutionException();
166			throw ee;
167
168	dl	1.3	} finally {
169	jsr166	1.20	for (Future<T> f : futures)
170	dl	1.4	f.cancel(true);
171	dl	1.3	}
172			}
173
174	dl	1.15	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	jsr166	1.20	public <T> T invokeAny(Collection<Callable<T>> tasks,
185			long timeout, TimeUnit unit)
186	dl	1.7	throws InterruptedException, ExecutionException, TimeoutException {
187	dl	1.15	return doInvokeAny(tasks, true, unit.toNanos(timeout));
188	dl	1.3	}
189
190	dl	1.9	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
191	dl	1.3	throws InterruptedException {
192			if (tasks == null)
193			throw new NullPointerException();
194	dl	1.6	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
195			boolean done = false;
196	dl	1.3	try {
197			for (Callable<T> t : tasks) {
198	peierls	1.21	RunnableFuture<T> f = newTaskFor(t);
199	dl	1.3	futures.add(f);
200			execute(f);
201			}
202	dl	1.6	for (Future<T> f : futures) {
203			if (!f.isDone()) {
204	jsr166	1.20	try {
205			f.get();
206	jsr166	1.19	} catch (CancellationException ignore) {
207			} catch (ExecutionException ignore) {
208	dl	1.6	}
209			}
210			}
211			done = true;
212	dl	1.3	return futures;
213			} finally {
214	dl	1.6	if (!done)
215	jsr166	1.20	for (Future<T> f : futures)
216	dl	1.4	f.cancel(true);
217	dl	1.3	}
218			}
219
220	jsr166	1.20	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
221			long timeout, TimeUnit unit)
222	dl	1.3	throws InterruptedException {
223			if (tasks == null \|\| unit == null)
224			throw new NullPointerException();
225			long nanos = unit.toNanos(timeout);
226	dl	1.6	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
227			boolean done = false;
228	dl	1.3	try {
229	jsr166	1.20	for (Callable<T> t : tasks)
230	peierls	1.21	futures.add(newTaskFor(t));
231	dl	1.16
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	jsr166	1.20	return futures;
244	dl	1.3	}
245	dl	1.16
246	dl	1.6	for (Future<T> f : futures) {
247			if (!f.isDone()) {
248	jsr166	1.20	if (nanos <= 0)
249			return futures;
250			try {
251			f.get(nanos, TimeUnit.NANOSECONDS);
252	jsr166	1.19	} catch (CancellationException ignore) {
253			} catch (ExecutionException ignore) {
254			} catch (TimeoutException toe) {
255	dl	1.6	return futures;
256			}
257	dl	1.8	long now = System.nanoTime();
258			nanos -= now - lastTime;
259			lastTime = now;
260	dl	1.6	}
261			}
262			done = true;
263	dl	1.3	return futures;
264			} finally {
265	dl	1.6	if (!done)
266	jsr166	1.20	for (Future<T> f : futures)
267	dl	1.4	f.cancel(true);
268	dl	1.3	}
269			}
270
271	tim	1.1	}