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 the default
 * {@link FutureTask} class provided in this package.  For example,
 * the the implementation of <tt>submit(Runnable)</tt> creates an
 * associated <tt>FutureTask</tt> that is executed and
 * returned. Subclasses overriding these methods to use different
 * {@link Future} implementations should do so consistently for each
 * of these methods.
 *
 * @since 1.5
 * @author Doug Lea
 */
public abstract class AbstractExecutorService implements ExecutorService {

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

    public <T> Future<T> submit(Runnable task, T result) {
        if (task == null) throw new NullPointerException();
        FutureTask<T> ftask = new FutureTask<T>(task, result);
        execute(ftask);
        return ftask;
    }

    public <T> Future<T> submit(Callable<T> task) {
        if (task == null) throw new NullPointerException();
        FutureTask<T> ftask = new FutureTask<T>(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) {
                FutureTask<T> f = new FutureTask<T>(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(new FutureTask<T>(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:	1.17
Committed:	Sat Dec 27 19:26:25 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.16:	+2 -2 lines
Log Message:	Headers reference Creative Commons
#	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 the default
15	* {@link FutureTask} class provided in this package. For example,
16	* the the implementation of <tt>submit(Runnable)</tt> creates an
17	* associated <tt>FutureTask</tt> that is executed and
18	* returned. Subclasses overriding these methods to use different
19	* {@link Future} implementations should do so consistently for each
20	* of these methods.
21	*
22	* @since 1.5
23	* @author Doug Lea
24	*/
25	public abstract class AbstractExecutorService implements ExecutorService {
26
27	public Future<?> submit(Runnable task) {
28	if (task == null) throw new NullPointerException();
29	FutureTask<Object> ftask = new FutureTask<Object>(task, null);
30	execute(ftask);
31	return ftask;
32	}
33
34	public <T> Future<T> submit(Runnable task, T result) {
35	if (task == null) throw new NullPointerException();
36	FutureTask<T> ftask = new FutureTask<T>(task, result);
37	execute(ftask);
38	return ftask;
39	}
40
41	public <T> Future<T> submit(Callable<T> task) {
42	if (task == null) throw new NullPointerException();
43	FutureTask<T> ftask = new FutureTask<T>(task);
44	execute(ftask);
45	return ftask;
46	}
47
48	/**
49	* the main mechanics of invokeAny.
50	*/
51	private <T> T doInvokeAny(Collection<Callable<T>> tasks,
52	boolean timed, long nanos)
53	throws InterruptedException, ExecutionException, TimeoutException {
54	if (tasks == null)
55	throw new NullPointerException();
56	int ntasks = tasks.size();
57	if (ntasks == 0)
58	throw new IllegalArgumentException();
59	List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
60	ExecutorCompletionService<T> ecs =
61	new ExecutorCompletionService<T>(this);
62
63	// For efficiency, especially in executors with limited
64	// parallelism, check to see if previously submitted tasks are
65	// done before submitting more of them. This interleaving,
66	// plus the exception mechanics account for messiness of main
67	// loop
68
69	try {
70	// Record exceptions so that if we fail to obtain any
71	// result, we can throw the last exception we got.
72	ExecutionException ee = null;
73	long lastTime = (timed)? System.nanoTime() : 0;
74	Iterator<Callable<T>> it = tasks.iterator();
75
76	// Start one task for sure; the rest incrementally
77	futures.add(ecs.submit(it.next()));
78	--ntasks;
79	int active = 1;
80
81	for (;;) {
82	Future<T> f = ecs.poll();
83	if (f == null) {
84	if (ntasks > 0) {
85	--ntasks;
86	futures.add(ecs.submit(it.next()));
87	++active;
88	}
89	else if (active == 0)
90	break;
91	else if (timed) {
92	f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
93	if (f == null)
94	throw new TimeoutException();
95	long now = System.nanoTime();
96	nanos -= now - lastTime;
97	lastTime = now;
98	}
99	else
100	f = ecs.take();
101	}
102	if (f != null) {
103	--active;
104	try {
105	return f.get();
106	} catch(InterruptedException ie) {
107	throw ie;
108	} catch(ExecutionException eex) {
109	ee = eex;
110	} catch(RuntimeException rex) {
111	ee = new ExecutionException(rex);
112	}
113	}
114	}
115
116	if (ee == null)
117	ee = new ExecutionException();
118	throw ee;
119
120	} finally {
121	for (Future<T> f : futures)
122	f.cancel(true);
123	}
124	}
125
126	public <T> T invokeAny(Collection<Callable<T>> tasks)
127	throws InterruptedException, ExecutionException {
128	try {
129	return doInvokeAny(tasks, false, 0);
130	} catch (TimeoutException cannotHappen) {
131	assert false;
132	return null;
133	}
134	}
135
136	public <T> T invokeAny(Collection<Callable<T>> tasks,
137	long timeout, TimeUnit unit)
138	throws InterruptedException, ExecutionException, TimeoutException {
139	return doInvokeAny(tasks, true, unit.toNanos(timeout));
140	}
141
142	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
143	throws InterruptedException {
144	if (tasks == null)
145	throw new NullPointerException();
146	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
147	boolean done = false;
148	try {
149	for (Callable<T> t : tasks) {
150	FutureTask<T> f = new FutureTask<T>(t);
151	futures.add(f);
152	execute(f);
153	}
154	for (Future<T> f : futures) {
155	if (!f.isDone()) {
156	try {
157	f.get();
158	} catch(CancellationException ignore) {
159	} catch(ExecutionException ignore) {
160	}
161	}
162	}
163	done = true;
164	return futures;
165	} finally {
166	if (!done)
167	for (Future<T> f : futures)
168	f.cancel(true);
169	}
170	}
171
172	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
173	long timeout, TimeUnit unit)
174	throws InterruptedException {
175	if (tasks == null \|\| unit == null)
176	throw new NullPointerException();
177	long nanos = unit.toNanos(timeout);
178	List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
179	boolean done = false;
180	try {
181	for (Callable<T> t : tasks)
182	futures.add(new FutureTask<T>(t));
183
184	long lastTime = System.nanoTime();
185
186	// Interleave time checks and calls to execute in case
187	// executor doesn't have any/much parallelism.
188	Iterator<Future<T>> it = futures.iterator();
189	while (it.hasNext()) {
190	execute((Runnable)(it.next()));
191	long now = System.nanoTime();
192	nanos -= now - lastTime;
193	lastTime = now;
194	if (nanos <= 0)
195	return futures;
196	}
197
198	for (Future<T> f : futures) {
199	if (!f.isDone()) {
200	if (nanos <= 0)
201	return futures;
202	try {
203	f.get(nanos, TimeUnit.NANOSECONDS);
204	} catch(CancellationException ignore) {
205	} catch(ExecutionException ignore) {
206	} catch(TimeoutException toe) {
207	return futures;
208	}
209	long now = System.nanoTime();
210	nanos -= now - lastTime;
211	lastTime = now;
212	}
213	}
214	done = true;
215	return futures;
216	} finally {
217	if (!done)
218	for (Future<T> f : futures)
219	f.cancel(true);
220	}
221	}
222
223	}