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; {...}
 *
 *    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:	1.23
Committed:	Fri May 20 16:25:51 2005 UTC (19 years ago) by dl
Branch:	MAIN
Changes since 1.22:	+3 -3 lines
Log Message:	fix syntax in sample code
#	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	dl	1.2	* Provides default implementation 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			* to return other <tt>RunnableFuture</tt> implementations than
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			* }
37			* // ... 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			* @param runnable the runnable task being wrapped
49			* @param value the default value for the returned future
50	dl	1.22	* @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	peierls	1.21	*/
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	dl	1.22	* @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	peierls	1.21	*/
69			protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
70			return new FutureTask<T>(callable);
71			}
72
73	dl	1.11	public Future<?> submit(Runnable task) {
74	dl	1.13	if (task == null) throw new NullPointerException();
75	peierls	1.21	RunnableFuture<Object> ftask = newTaskFor(task, null);
76	tim	1.1	execute(ftask);
77			return ftask;
78			}
79
80	dl	1.13	public <T> Future<T> submit(Runnable task, T result) {
81			if (task == null) throw new NullPointerException();
82	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task, result);
83	dl	1.13	execute(ftask);
84			return ftask;
85			}
86
87	tim	1.1	public <T> Future<T> submit(Callable<T> task) {
88	dl	1.13	if (task == null) throw new NullPointerException();
89	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task);
90	tim	1.1	execute(ftask);
91			return ftask;
92			}
93
94	dl	1.15	/**
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	dl	1.3	if (tasks == null)
101			throw new NullPointerException();
102	dl	1.15	int ntasks = tasks.size();
103			if (ntasks == 0)
104	dl	1.7	throw new IllegalArgumentException();
105	dl	1.15	List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
106	jsr166	1.20	ExecutorCompletionService<T> ecs =
107	dl	1.7	new ExecutorCompletionService<T>(this);
108	dl	1.15
109			// For efficiency, especially in executors with limited
110			// parallelism, check to see if previously submitted tasks are
111	dl	1.18	// done before submitting more of them. This interleaving
112	dl	1.15	// plus the exception mechanics account for messiness of main
113	dl	1.18	// loop.
114	dl	1.15
115	dl	1.3	try {
116	dl	1.15	// Record exceptions so that if we fail to obtain any
117			// result, we can throw the last exception we got.
118	dl	1.7	ExecutionException ee = null;
119	dl	1.15	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	jsr166	1.20	Future<T> f = ecs.poll();
129	dl	1.15	if (f == null) {
130			if (ntasks > 0) {
131			--ntasks;
132			futures.add(ecs.submit(it.next()));
133			++active;
134			}
135	jsr166	1.20	else if (active == 0)
136	dl	1.15	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	jsr166	1.20	else
146	dl	1.15	f = ecs.take();
147			}
148			if (f != null) {
149			--active;
150			try {
151			return f.get();
152	jsr166	1.19	} catch (InterruptedException ie) {
153	dl	1.15	throw ie;
154	jsr166	1.19	} catch (ExecutionException eex) {
155	dl	1.15	ee = eex;
156	jsr166	1.19	} catch (RuntimeException rex) {
157	dl	1.15	ee = new ExecutionException(rex);
158			}
159	dl	1.7	}
160	jsr166	1.20	}
161	dl	1.15
162			if (ee == null)
163			ee = new ExecutionException();
164			throw ee;
165
166	dl	1.3	} finally {
167	jsr166	1.20	for (Future<T> f : futures)
168	dl	1.4	f.cancel(true);
169	dl	1.3	}
170			}
171
172	dl	1.15	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	jsr166	1.20	public <T> T invokeAny(Collection<Callable<T>> tasks,
183			long timeout, TimeUnit unit)
184	dl	1.7	throws InterruptedException, ExecutionException, TimeoutException {
185	dl	1.15	return doInvokeAny(tasks, true, unit.toNanos(timeout));
186	dl	1.3	}
187
188	dl	1.9	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
189	dl	1.3	throws InterruptedException {
190			if (tasks == null)
191			throw new NullPointerException();
192	dl	1.6	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
193			boolean done = false;
194	dl	1.3	try {
195			for (Callable<T> t : tasks) {
196	peierls	1.21	RunnableFuture<T> f = newTaskFor(t);
197	dl	1.3	futures.add(f);
198			execute(f);
199			}
200	dl	1.6	for (Future<T> f : futures) {
201			if (!f.isDone()) {
202	jsr166	1.20	try {
203			f.get();
204	jsr166	1.19	} catch (CancellationException ignore) {
205			} catch (ExecutionException ignore) {
206	dl	1.6	}
207			}
208			}
209			done = true;
210	dl	1.3	return futures;
211			} finally {
212	dl	1.6	if (!done)
213	jsr166	1.20	for (Future<T> f : futures)
214	dl	1.4	f.cancel(true);
215	dl	1.3	}
216			}
217
218	jsr166	1.20	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
219			long timeout, TimeUnit unit)
220	dl	1.3	throws InterruptedException {
221			if (tasks == null \|\| unit == null)
222			throw new NullPointerException();
223			long nanos = unit.toNanos(timeout);
224	dl	1.6	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
225			boolean done = false;
226	dl	1.3	try {
227	jsr166	1.20	for (Callable<T> t : tasks)
228	peierls	1.21	futures.add(newTaskFor(t));
229	dl	1.16
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	jsr166	1.20	return futures;
242	dl	1.3	}
243	dl	1.16
244	dl	1.6	for (Future<T> f : futures) {
245			if (!f.isDone()) {
246	jsr166	1.20	if (nanos <= 0)
247			return futures;
248			try {
249			f.get(nanos, TimeUnit.NANOSECONDS);
250	jsr166	1.19	} catch (CancellationException ignore) {
251			} catch (ExecutionException ignore) {
252			} catch (TimeoutException toe) {
253	dl	1.6	return futures;
254			}
255	dl	1.8	long now = System.nanoTime();
256			nanos -= now - lastTime;
257			lastTime = now;
258	dl	1.6	}
259			}
260			done = true;
261	dl	1.3	return futures;
262			} finally {
263	dl	1.6	if (!done)
264	jsr166	1.20	for (Future<T> f : futures)
265	dl	1.4	f.cancel(true);
266	dl	1.3	}
267			}
268
269	tim	1.1	}