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root/jsr166/jsr166/src/jdk7/java/util/concurrent/Executors.java
Revision: 1.2
Committed: Wed Jan 16 01:39:37 2013 UTC (11 years, 4 months ago) by jsr166
Branch: MAIN
Changes since 1.1: +18 -18 lines
Log Message:
<tt> -> {@code

File Contents

# User Rev Content
1 dl 1.1 /*
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/publicdomain/zero/1.0/
5     */
6    
7     package java.util.concurrent;
8     import java.util.*;
9     import java.util.concurrent.atomic.AtomicInteger;
10     import java.security.AccessControlContext;
11     import java.security.AccessController;
12     import java.security.PrivilegedAction;
13     import java.security.PrivilegedExceptionAction;
14     import java.security.PrivilegedActionException;
15     import java.security.AccessControlException;
16     import sun.security.util.SecurityConstants;
17    
18     /**
19     * Factory and utility methods for {@link Executor}, {@link
20     * ExecutorService}, {@link ScheduledExecutorService}, {@link
21     * ThreadFactory}, and {@link Callable} classes defined in this
22     * package. This class supports the following kinds of methods:
23     *
24     * <ul>
25     * <li> Methods that create and return an {@link ExecutorService}
26     * set up with commonly useful configuration settings.
27     * <li> Methods that create and return a {@link ScheduledExecutorService}
28     * set up with commonly useful configuration settings.
29     * <li> Methods that create and return a "wrapped" ExecutorService, that
30     * disables reconfiguration by making implementation-specific methods
31     * inaccessible.
32     * <li> Methods that create and return a {@link ThreadFactory}
33     * that sets newly created threads to a known state.
34     * <li> Methods that create and return a {@link Callable}
35     * out of other closure-like forms, so they can be used
36 jsr166 1.2 * in execution methods requiring {@code Callable}.
37 dl 1.1 * </ul>
38     *
39     * @since 1.5
40     * @author Doug Lea
41     */
42     public class Executors {
43    
44     /**
45     * Creates a thread pool that reuses a fixed number of threads
46     * operating off a shared unbounded queue. At any point, at most
47 jsr166 1.2 * {@code nThreads} threads will be active processing tasks.
48 dl 1.1 * If additional tasks are submitted when all threads are active,
49     * they will wait in the queue until a thread is available.
50     * If any thread terminates due to a failure during execution
51     * prior to shutdown, a new one will take its place if needed to
52     * execute subsequent tasks. The threads in the pool will exist
53     * until it is explicitly {@link ExecutorService#shutdown shutdown}.
54     *
55     * @param nThreads the number of threads in the pool
56     * @return the newly created thread pool
57     * @throws IllegalArgumentException if {@code nThreads <= 0}
58     */
59     public static ExecutorService newFixedThreadPool(int nThreads) {
60     return new ThreadPoolExecutor(nThreads, nThreads,
61     0L, TimeUnit.MILLISECONDS,
62     new LinkedBlockingQueue<Runnable>());
63     }
64    
65     /**
66     * Creates a thread pool that maintains enough threads to support
67     * the given parallelism level, and may use multiple queues to
68     * reduce contention. The parallelism level corresponds to the
69     * maximum number of threads actively engaged in, or available to
70     * engage in, task processing. The actual number of threads may
71     * grow and shrink dynamically. A work-stealing pool makes no
72     * guarantees about the order in which submitted tasks are
73     * executed.
74     *
75     * @param parallelism the targeted parallelism level
76     * @return the newly created thread pool
77     * @throws IllegalArgumentException if {@code parallelism <= 0}
78     * @since 1.8
79     */
80     public static ExecutorService newWorkStealingPool(int parallelism) {
81     return new ForkJoinPool
82     (parallelism,
83     ForkJoinPool.defaultForkJoinWorkerThreadFactory,
84     null, true);
85     }
86    
87     /**
88     * Creates a work-stealing thread pool using all
89     * (@link Runtime#availableProcessors available processors}
90     * as its target parallelism level.
91     * @return the newly created thread pool
92     * @since 1.8
93     */
94     public static ExecutorService newWorkStealingPool() {
95     return new ForkJoinPool
96     (Runtime.getRuntime().availableProcessors(),
97     ForkJoinPool.defaultForkJoinWorkerThreadFactory,
98     null, true);
99     }
100    
101     /**
102     * Creates a thread pool that reuses a fixed number of threads
103     * operating off a shared unbounded queue, using the provided
104     * ThreadFactory to create new threads when needed. At any point,
105 jsr166 1.2 * at most {@code nThreads} threads will be active processing
106 dl 1.1 * tasks. If additional tasks are submitted when all threads are
107     * active, they will wait in the queue until a thread is
108     * available. If any thread terminates due to a failure during
109     * execution prior to shutdown, a new one will take its place if
110     * needed to execute subsequent tasks. The threads in the pool will
111     * exist until it is explicitly {@link ExecutorService#shutdown
112     * shutdown}.
113     *
114     * @param nThreads the number of threads in the pool
115     * @param threadFactory the factory to use when creating new threads
116     * @return the newly created thread pool
117     * @throws NullPointerException if threadFactory is null
118     * @throws IllegalArgumentException if {@code nThreads <= 0}
119     */
120     public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
121     return new ThreadPoolExecutor(nThreads, nThreads,
122     0L, TimeUnit.MILLISECONDS,
123     new LinkedBlockingQueue<Runnable>(),
124     threadFactory);
125     }
126    
127     /**
128     * Creates an Executor that uses a single worker thread operating
129     * off an unbounded queue. (Note however that if this single
130     * thread terminates due to a failure during execution prior to
131     * shutdown, a new one will take its place if needed to execute
132     * subsequent tasks.) Tasks are guaranteed to execute
133     * sequentially, and no more than one task will be active at any
134     * given time. Unlike the otherwise equivalent
135 jsr166 1.2 * {@code newFixedThreadPool(1)} the returned executor is
136 dl 1.1 * guaranteed not to be reconfigurable to use additional threads.
137     *
138     * @return the newly created single-threaded Executor
139     */
140     public static ExecutorService newSingleThreadExecutor() {
141     return new FinalizableDelegatedExecutorService
142     (new ThreadPoolExecutor(1, 1,
143     0L, TimeUnit.MILLISECONDS,
144     new LinkedBlockingQueue<Runnable>()));
145     }
146    
147     /**
148     * Creates an Executor that uses a single worker thread operating
149     * off an unbounded queue, and uses the provided ThreadFactory to
150     * create a new thread when needed. Unlike the otherwise
151 jsr166 1.2 * equivalent {@code newFixedThreadPool(1, threadFactory)} the
152 dl 1.1 * returned executor is guaranteed not to be reconfigurable to use
153     * additional threads.
154     *
155     * @param threadFactory the factory to use when creating new
156     * threads
157     *
158     * @return the newly created single-threaded Executor
159     * @throws NullPointerException if threadFactory is null
160     */
161     public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
162     return new FinalizableDelegatedExecutorService
163     (new ThreadPoolExecutor(1, 1,
164     0L, TimeUnit.MILLISECONDS,
165     new LinkedBlockingQueue<Runnable>(),
166     threadFactory));
167     }
168    
169     /**
170     * Creates a thread pool that creates new threads as needed, but
171     * will reuse previously constructed threads when they are
172     * available. These pools will typically improve the performance
173     * of programs that execute many short-lived asynchronous tasks.
174 jsr166 1.2 * Calls to {@code execute} will reuse previously constructed
175 dl 1.1 * threads if available. If no existing thread is available, a new
176     * thread will be created and added to the pool. Threads that have
177     * not been used for sixty seconds are terminated and removed from
178     * the cache. Thus, a pool that remains idle for long enough will
179     * not consume any resources. Note that pools with similar
180     * properties but different details (for example, timeout parameters)
181     * may be created using {@link ThreadPoolExecutor} constructors.
182     *
183     * @return the newly created thread pool
184     */
185     public static ExecutorService newCachedThreadPool() {
186     return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
187     60L, TimeUnit.SECONDS,
188     new SynchronousQueue<Runnable>());
189     }
190    
191     /**
192     * Creates a thread pool that creates new threads as needed, but
193     * will reuse previously constructed threads when they are
194     * available, and uses the provided
195     * ThreadFactory to create new threads when needed.
196     * @param threadFactory the factory to use when creating new threads
197     * @return the newly created thread pool
198     * @throws NullPointerException if threadFactory is null
199     */
200     public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
201     return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
202     60L, TimeUnit.SECONDS,
203     new SynchronousQueue<Runnable>(),
204     threadFactory);
205     }
206    
207     /**
208     * Creates a single-threaded executor that can schedule commands
209     * to run after a given delay, or to execute periodically.
210     * (Note however that if this single
211     * thread terminates due to a failure during execution prior to
212     * shutdown, a new one will take its place if needed to execute
213     * subsequent tasks.) Tasks are guaranteed to execute
214     * sequentially, and no more than one task will be active at any
215     * given time. Unlike the otherwise equivalent
216 jsr166 1.2 * {@code newScheduledThreadPool(1)} the returned executor is
217 dl 1.1 * guaranteed not to be reconfigurable to use additional threads.
218     * @return the newly created scheduled executor
219     */
220     public static ScheduledExecutorService newSingleThreadScheduledExecutor() {
221     return new DelegatedScheduledExecutorService
222     (new ScheduledThreadPoolExecutor(1));
223     }
224    
225     /**
226     * Creates a single-threaded executor that can schedule commands
227     * to run after a given delay, or to execute periodically. (Note
228     * however that if this single thread terminates due to a failure
229     * during execution prior to shutdown, a new one will take its
230     * place if needed to execute subsequent tasks.) Tasks are
231     * guaranteed to execute sequentially, and no more than one task
232     * will be active at any given time. Unlike the otherwise
233 jsr166 1.2 * equivalent {@code newScheduledThreadPool(1, threadFactory)}
234 dl 1.1 * the returned executor is guaranteed not to be reconfigurable to
235     * use additional threads.
236     * @param threadFactory the factory to use when creating new
237     * threads
238     * @return a newly created scheduled executor
239     * @throws NullPointerException if threadFactory is null
240     */
241     public static ScheduledExecutorService newSingleThreadScheduledExecutor(ThreadFactory threadFactory) {
242     return new DelegatedScheduledExecutorService
243     (new ScheduledThreadPoolExecutor(1, threadFactory));
244     }
245    
246     /**
247     * Creates a thread pool that can schedule commands to run after a
248     * given delay, or to execute periodically.
249     * @param corePoolSize the number of threads to keep in the pool,
250     * even if they are idle.
251     * @return a newly created scheduled thread pool
252     * @throws IllegalArgumentException if {@code corePoolSize < 0}
253     */
254     public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
255     return new ScheduledThreadPoolExecutor(corePoolSize);
256     }
257    
258     /**
259     * Creates a thread pool that can schedule commands to run after a
260     * given delay, or to execute periodically.
261     * @param corePoolSize the number of threads to keep in the pool,
262     * even if they are idle.
263     * @param threadFactory the factory to use when the executor
264     * creates a new thread.
265     * @return a newly created scheduled thread pool
266     * @throws IllegalArgumentException if {@code corePoolSize < 0}
267     * @throws NullPointerException if threadFactory is null
268     */
269     public static ScheduledExecutorService newScheduledThreadPool(
270     int corePoolSize, ThreadFactory threadFactory) {
271     return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
272     }
273    
274     /**
275     * Returns an object that delegates all defined {@link
276     * ExecutorService} methods to the given executor, but not any
277     * other methods that might otherwise be accessible using
278     * casts. This provides a way to safely "freeze" configuration and
279     * disallow tuning of a given concrete implementation.
280     * @param executor the underlying implementation
281 jsr166 1.2 * @return an {@code ExecutorService} instance
282 dl 1.1 * @throws NullPointerException if executor null
283     */
284     public static ExecutorService unconfigurableExecutorService(ExecutorService executor) {
285     if (executor == null)
286     throw new NullPointerException();
287     return new DelegatedExecutorService(executor);
288     }
289    
290     /**
291     * Returns an object that delegates all defined {@link
292     * ScheduledExecutorService} methods to the given executor, but
293     * not any other methods that might otherwise be accessible using
294     * casts. This provides a way to safely "freeze" configuration and
295     * disallow tuning of a given concrete implementation.
296     * @param executor the underlying implementation
297 jsr166 1.2 * @return a {@code ScheduledExecutorService} instance
298 dl 1.1 * @throws NullPointerException if executor null
299     */
300     public static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor) {
301     if (executor == null)
302     throw new NullPointerException();
303     return new DelegatedScheduledExecutorService(executor);
304     }
305    
306     /**
307     * Returns a default thread factory used to create new threads.
308     * This factory creates all new threads used by an Executor in the
309     * same {@link ThreadGroup}. If there is a {@link
310     * java.lang.SecurityManager}, it uses the group of {@link
311     * System#getSecurityManager}, else the group of the thread
312 jsr166 1.2 * invoking this {@code defaultThreadFactory} method. Each new
313 dl 1.1 * thread is created as a non-daemon thread with priority set to
314 jsr166 1.2 * the smaller of {@code Thread.NORM_PRIORITY} and the maximum
315 dl 1.1 * priority permitted in the thread group. New threads have names
316     * accessible via {@link Thread#getName} of
317     * <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
318     * number of this factory, and <em>M</em> is the sequence number
319     * of the thread created by this factory.
320     * @return a thread factory
321     */
322     public static ThreadFactory defaultThreadFactory() {
323     return new DefaultThreadFactory();
324     }
325    
326     /**
327     * Returns a thread factory used to create new threads that
328     * have the same permissions as the current thread.
329     * This factory creates threads with the same settings as {@link
330     * Executors#defaultThreadFactory}, additionally setting the
331     * AccessControlContext and contextClassLoader of new threads to
332     * be the same as the thread invoking this
333 jsr166 1.2 * {@code privilegedThreadFactory} method. A new
334     * {@code privilegedThreadFactory} can be created within an
335 dl 1.1 * {@link AccessController#doPrivileged} action setting the
336     * current thread's access control context to create threads with
337     * the selected permission settings holding within that action.
338     *
339     * <p>Note that while tasks running within such threads will have
340     * the same access control and class loader settings as the
341     * current thread, they need not have the same {@link
342     * java.lang.ThreadLocal} or {@link
343     * java.lang.InheritableThreadLocal} values. If necessary,
344     * particular values of thread locals can be set or reset before
345     * any task runs in {@link ThreadPoolExecutor} subclasses using
346     * {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
347     * necessary to initialize worker threads to have the same
348     * InheritableThreadLocal settings as some other designated
349     * thread, you can create a custom ThreadFactory in which that
350     * thread waits for and services requests to create others that
351     * will inherit its values.
352     *
353     * @return a thread factory
354     * @throws AccessControlException if the current access control
355     * context does not have permission to both get and set context
356     * class loader.
357     */
358     public static ThreadFactory privilegedThreadFactory() {
359     return new PrivilegedThreadFactory();
360     }
361    
362     /**
363     * Returns a {@link Callable} object that, when
364     * called, runs the given task and returns the given result. This
365     * can be useful when applying methods requiring a
366 jsr166 1.2 * {@code Callable} to an otherwise resultless action.
367 dl 1.1 * @param task the task to run
368     * @param result the result to return
369     * @return a callable object
370     * @throws NullPointerException if task null
371     */
372     public static <T> Callable<T> callable(Runnable task, T result) {
373     if (task == null)
374     throw new NullPointerException();
375     return new RunnableAdapter<T>(task, result);
376     }
377    
378     /**
379     * Returns a {@link Callable} object that, when
380 jsr166 1.2 * called, runs the given task and returns {@code null}.
381 dl 1.1 * @param task the task to run
382     * @return a callable object
383     * @throws NullPointerException if task null
384     */
385     public static Callable<Object> callable(Runnable task) {
386     if (task == null)
387     throw new NullPointerException();
388     return new RunnableAdapter<Object>(task, null);
389     }
390    
391     /**
392     * Returns a {@link Callable} object that, when
393     * called, runs the given privileged action and returns its result.
394     * @param action the privileged action to run
395     * @return a callable object
396     * @throws NullPointerException if action null
397     */
398     public static Callable<Object> callable(final PrivilegedAction<?> action) {
399     if (action == null)
400     throw new NullPointerException();
401     return new Callable<Object>() {
402     public Object call() { return action.run(); }};
403     }
404    
405     /**
406     * Returns a {@link Callable} object that, when
407     * called, runs the given privileged exception action and returns
408     * its result.
409     * @param action the privileged exception action to run
410     * @return a callable object
411     * @throws NullPointerException if action null
412     */
413     public static Callable<Object> callable(final PrivilegedExceptionAction<?> action) {
414     if (action == null)
415     throw new NullPointerException();
416     return new Callable<Object>() {
417     public Object call() throws Exception { return action.run(); }};
418     }
419    
420     /**
421     * Returns a {@link Callable} object that will, when
422 jsr166 1.2 * called, execute the given {@code callable} under the current
423 dl 1.1 * access control context. This method should normally be
424     * invoked within an {@link AccessController#doPrivileged} action
425     * to create callables that will, if possible, execute under the
426     * selected permission settings holding within that action; or if
427     * not possible, throw an associated {@link
428     * AccessControlException}.
429     * @param callable the underlying task
430     * @return a callable object
431     * @throws NullPointerException if callable null
432     */
433     public static <T> Callable<T> privilegedCallable(Callable<T> callable) {
434     if (callable == null)
435     throw new NullPointerException();
436     return new PrivilegedCallable<T>(callable);
437     }
438    
439     /**
440     * Returns a {@link Callable} object that will, when
441 jsr166 1.2 * called, execute the given {@code callable} under the current
442 dl 1.1 * access control context, with the current context class loader
443     * as the context class loader. This method should normally be
444     * invoked within an {@link AccessController#doPrivileged} action
445     * to create callables that will, if possible, execute under the
446     * selected permission settings holding within that action; or if
447     * not possible, throw an associated {@link
448     * AccessControlException}.
449     * @param callable the underlying task
450     *
451     * @return a callable object
452     * @throws NullPointerException if callable null
453     * @throws AccessControlException if the current access control
454     * context does not have permission to both set and get context
455     * class loader.
456     */
457     public static <T> Callable<T> privilegedCallableUsingCurrentClassLoader(Callable<T> callable) {
458     if (callable == null)
459     throw new NullPointerException();
460     return new PrivilegedCallableUsingCurrentClassLoader<T>(callable);
461     }
462    
463     // Non-public classes supporting the public methods
464    
465     /**
466     * A callable that runs given task and returns given result
467     */
468     static final class RunnableAdapter<T> implements Callable<T> {
469     final Runnable task;
470     final T result;
471     RunnableAdapter(Runnable task, T result) {
472     this.task = task;
473     this.result = result;
474     }
475     public T call() {
476     task.run();
477     return result;
478     }
479     }
480    
481     /**
482     * A callable that runs under established access control settings
483     */
484     static final class PrivilegedCallable<T> implements Callable<T> {
485     private final Callable<T> task;
486     private final AccessControlContext acc;
487    
488     PrivilegedCallable(Callable<T> task) {
489     this.task = task;
490     this.acc = AccessController.getContext();
491     }
492    
493     public T call() throws Exception {
494     try {
495     return AccessController.doPrivileged(
496     new PrivilegedExceptionAction<T>() {
497     public T run() throws Exception {
498     return task.call();
499     }
500     }, acc);
501     } catch (PrivilegedActionException e) {
502     throw e.getException();
503     }
504     }
505     }
506    
507     /**
508     * A callable that runs under established access control settings and
509     * current ClassLoader
510     */
511     static final class PrivilegedCallableUsingCurrentClassLoader<T> implements Callable<T> {
512     private final Callable<T> task;
513     private final AccessControlContext acc;
514     private final ClassLoader ccl;
515    
516     PrivilegedCallableUsingCurrentClassLoader(Callable<T> task) {
517     SecurityManager sm = System.getSecurityManager();
518     if (sm != null) {
519     // Calls to getContextClassLoader from this class
520     // never trigger a security check, but we check
521     // whether our callers have this permission anyways.
522     sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
523    
524     // Whether setContextClassLoader turns out to be necessary
525     // or not, we fail fast if permission is not available.
526     sm.checkPermission(new RuntimePermission("setContextClassLoader"));
527     }
528     this.task = task;
529     this.acc = AccessController.getContext();
530     this.ccl = Thread.currentThread().getContextClassLoader();
531     }
532    
533     public T call() throws Exception {
534     try {
535     return AccessController.doPrivileged(
536     new PrivilegedExceptionAction<T>() {
537     public T run() throws Exception {
538     Thread t = Thread.currentThread();
539     ClassLoader cl = t.getContextClassLoader();
540     if (ccl == cl) {
541     return task.call();
542     } else {
543     t.setContextClassLoader(ccl);
544     try {
545     return task.call();
546     } finally {
547     t.setContextClassLoader(cl);
548     }
549     }
550     }
551     }, acc);
552     } catch (PrivilegedActionException e) {
553     throw e.getException();
554     }
555     }
556     }
557    
558     /**
559     * The default thread factory
560     */
561     static class DefaultThreadFactory implements ThreadFactory {
562     private static final AtomicInteger poolNumber = new AtomicInteger(1);
563     private final ThreadGroup group;
564     private final AtomicInteger threadNumber = new AtomicInteger(1);
565     private final String namePrefix;
566    
567     DefaultThreadFactory() {
568     SecurityManager s = System.getSecurityManager();
569     group = (s != null) ? s.getThreadGroup() :
570     Thread.currentThread().getThreadGroup();
571     namePrefix = "pool-" +
572     poolNumber.getAndIncrement() +
573     "-thread-";
574     }
575    
576     public Thread newThread(Runnable r) {
577     Thread t = new Thread(group, r,
578     namePrefix + threadNumber.getAndIncrement(),
579     0);
580     if (t.isDaemon())
581     t.setDaemon(false);
582     if (t.getPriority() != Thread.NORM_PRIORITY)
583     t.setPriority(Thread.NORM_PRIORITY);
584     return t;
585     }
586     }
587    
588     /**
589     * Thread factory capturing access control context and class loader
590     */
591     static class PrivilegedThreadFactory extends DefaultThreadFactory {
592     private final AccessControlContext acc;
593     private final ClassLoader ccl;
594    
595     PrivilegedThreadFactory() {
596     super();
597     SecurityManager sm = System.getSecurityManager();
598     if (sm != null) {
599     // Calls to getContextClassLoader from this class
600     // never trigger a security check, but we check
601     // whether our callers have this permission anyways.
602     sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
603    
604     // Fail fast
605     sm.checkPermission(new RuntimePermission("setContextClassLoader"));
606     }
607     this.acc = AccessController.getContext();
608     this.ccl = Thread.currentThread().getContextClassLoader();
609     }
610    
611     public Thread newThread(final Runnable r) {
612     return super.newThread(new Runnable() {
613     public void run() {
614     AccessController.doPrivileged(new PrivilegedAction<Void>() {
615     public Void run() {
616     Thread.currentThread().setContextClassLoader(ccl);
617     r.run();
618     return null;
619     }
620     }, acc);
621     }
622     });
623     }
624     }
625    
626     /**
627     * A wrapper class that exposes only the ExecutorService methods
628     * of an ExecutorService implementation.
629     */
630     static class DelegatedExecutorService extends AbstractExecutorService {
631     private final ExecutorService e;
632     DelegatedExecutorService(ExecutorService executor) { e = executor; }
633     public void execute(Runnable command) { e.execute(command); }
634     public void shutdown() { e.shutdown(); }
635     public List<Runnable> shutdownNow() { return e.shutdownNow(); }
636     public boolean isShutdown() { return e.isShutdown(); }
637     public boolean isTerminated() { return e.isTerminated(); }
638     public boolean awaitTermination(long timeout, TimeUnit unit)
639     throws InterruptedException {
640     return e.awaitTermination(timeout, unit);
641     }
642     public Future<?> submit(Runnable task) {
643     return e.submit(task);
644     }
645     public <T> Future<T> submit(Callable<T> task) {
646     return e.submit(task);
647     }
648     public <T> Future<T> submit(Runnable task, T result) {
649     return e.submit(task, result);
650     }
651     public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
652     throws InterruptedException {
653     return e.invokeAll(tasks);
654     }
655     public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
656     long timeout, TimeUnit unit)
657     throws InterruptedException {
658     return e.invokeAll(tasks, timeout, unit);
659     }
660     public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
661     throws InterruptedException, ExecutionException {
662     return e.invokeAny(tasks);
663     }
664     public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
665     long timeout, TimeUnit unit)
666     throws InterruptedException, ExecutionException, TimeoutException {
667     return e.invokeAny(tasks, timeout, unit);
668     }
669     }
670    
671     static class FinalizableDelegatedExecutorService
672     extends DelegatedExecutorService {
673     FinalizableDelegatedExecutorService(ExecutorService executor) {
674     super(executor);
675     }
676     protected void finalize() {
677     super.shutdown();
678     }
679     }
680    
681     /**
682     * A wrapper class that exposes only the ScheduledExecutorService
683     * methods of a ScheduledExecutorService implementation.
684     */
685     static class DelegatedScheduledExecutorService
686     extends DelegatedExecutorService
687     implements ScheduledExecutorService {
688     private final ScheduledExecutorService e;
689     DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
690     super(executor);
691     e = executor;
692     }
693     public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
694     return e.schedule(command, delay, unit);
695     }
696     public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
697     return e.schedule(callable, delay, unit);
698     }
699     public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
700     return e.scheduleAtFixedRate(command, initialDelay, period, unit);
701     }
702     public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
703     return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
704     }
705     }
706    
707     /** Cannot instantiate. */
708     private Executors() {}
709     }