util/concurrent/Executors.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

package java.util.concurrent;
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;

/**
 * Factory and utility methods for {@link Executor}, {@link
 * ExecutorService}, and {@link ThreadFactory} classes defined in this
 * package.
 *
 * @since 1.5
 * @author Doug Lea
 */
public class Executors {

    /**
     * Creates a thread pool that reuses a fixed set of threads
     * operating off a shared unbounded queue. If any thread
     * terminates due to a failure during execution prior to shutdown,
     * a new one will take its place if needed to execute subsequent
     * tasks.
     *
     * @param nThreads the number of threads in the pool
     * @return the newly created thread pool
     */
    public static ExecutorService newFixedThreadPool(int nThreads) {
        return new ThreadPoolExecutor(nThreads, nThreads,
                                      0L, TimeUnit.MILLISECONDS,
                                      new LinkedBlockingQueue<Runnable>());
    }

    /**
     * Creates a thread pool that reuses a fixed set of threads
     * operating off a shared unbounded queue, using the provided
     * ThreadFactory to create new threads when needed.
     *
     * @param nThreads the number of threads in the pool
     * @param threadFactory the factory to use when creating new threads
     * @return the newly created thread pool
     */
    public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
        return new ThreadPoolExecutor(nThreads, nThreads,
                                      0L, TimeUnit.MILLISECONDS,
                                      new LinkedBlockingQueue<Runnable>(),
                                      threadFactory);
    }

    /**
     * Creates an Executor that uses a single worker thread operating
     * off an unbounded queue. (Note however that if this single
     * thread terminates due to a failure during execution prior to
     * shutdown, a new one will take its place if needed to execute
     * subsequent tasks.)  Tasks are guaranteed to execute
     * sequentially, and no more than one task will be active at any
     * given time. The returned executor cannot be reconfigured
     * to use additional threads.
     *
     * @return the newly-created single-threaded Executor
     */
    public static ExecutorService newSingleThreadExecutor() {
        return unconfigurableExecutorService
            (new ThreadPoolExecutor(1, 1,
                                    0L, TimeUnit.MILLISECONDS,
                                    new LinkedBlockingQueue<Runnable>()));
    }

    /**
     * Creates an Executor that uses a single worker thread operating
     * off an unbounded queue, and uses the provided ThreadFactory to
     * create a new thread when needed. The returned executor cannot be
     * reconfigured to use additional threads.
     * @param threadFactory the factory to use when creating new
     * threads
     *
     * @return the newly-created single-threaded Executor
     */
    public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
        return unconfigurableExecutorService
            (new ThreadPoolExecutor(1, 1,
                                    0L, TimeUnit.MILLISECONDS,
                                    new LinkedBlockingQueue<Runnable>(),
                                    threadFactory));
    }

    /**
     * Creates a thread pool that creates new threads as needed, but
     * will reuse previously constructed threads when they are
     * available.  These pools will typically improve the performance
     * of programs that execute many short-lived asynchronous tasks.
     * Calls to <tt>execute</tt> will reuse previously constructed
     * threads if available. If no existing thread is available, a new
     * thread will be created and added to the pool. Threads that have
     * not been used for sixty seconds are terminated and removed from
     * the cache. Thus, a pool that remains idle for long enough will
     * not consume any resources. Note that pools with similar
     * properties but different details (for example, timeout parameters)
     * may be created using {@link ThreadPoolExecutor} constructors.
     *
     * @return the newly created thread pool
     */
    public static ExecutorService newCachedThreadPool() {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                      60, TimeUnit.SECONDS,
                                      new SynchronousQueue<Runnable>());
    }

    /**
     * Creates a thread pool that creates new threads as needed, but
     * will reuse previously constructed threads when they are
     * available, and uses the provided
     * ThreadFactory to create new threads when needed.
     * @param threadFactory the factory to use when creating new threads
     * @return the newly created thread pool
     */
    public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                      60, TimeUnit.SECONDS,
                                      new SynchronousQueue<Runnable>(),
                                      threadFactory);
    }
   
    /**
     * Creates a thread pool that can schedule commands to run after a 
     * given delay, or to execute periodically.
     * @return a newly created scheduled thread pool with termination management
     */
    public static ScheduledExecutorService newScheduledThreadPool() {
        return newScheduledThreadPool(1);
    }
    
    /**
     * Creates a thread pool that can schedule commands to run after a 
     * given delay, or to execute periodically.
     * @param corePoolSize the number of threads to keep in the pool,
     * even if they are idle.
     * @return a newly created scheduled thread pool with termination management
     */
    public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
        return new ScheduledThreadPoolExecutor(corePoolSize);
}

    /**
     * Creates a thread pool that can schedule commands to run after a 
     * given delay, or to execute periodically.
     * @param corePoolSize the number of threads to keep in the pool,
     * even if they are idle.
     * @param threadFactory the factory to use when the executor
     * creates a new thread. 
     * @return a newly created scheduled thread pool with termination management
     */
    public static ScheduledExecutorService newScheduledThreadPool(
            int corePoolSize, ThreadFactory threadFactory) {
        return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
    }


    /**
     * Creates and returns an object that delegates all defined {@link
     * ExecutorService} methods to the given executor, but not any
     * other methods that might otherwise be accessible using
     * casts. This provides a way to safely "freeze" configuration and
     * disallow tuning of a given concrete implementation.
     * @param executor the underlying implementation
     * @return an <tt>ExecutorService</tt> instance
     * @throws NullPointerException if executor null
     */
    public static ExecutorService unconfigurableExecutorService(ExecutorService executor) {
        if (executor == null)
            throw new NullPointerException();
        return new DelegatedExecutorService(executor);
    }

    /**
     * Creates and returns an object that delegates all defined {@link
     * ScheduledExecutorService} methods to the given executor, but
     * not any other methods that might otherwise be accessible using
     * casts. This provides a way to safely "freeze" configuration and
     * disallow tuning of a given concrete implementation.
     * @param executor the underlying implementation
     * @return a <tt>ScheduledExecutorService</tt> instance
     * @throws NullPointerException if executor null
     */
    public static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor) {
        if (executor == null)
            throw new NullPointerException();
        return new DelegatedScheduledExecutorService(executor);
    }
        
    /**
     * Return a default thread factory used to create new threads.
     * This factory creates all new threads used by an Executor in the
     * same {@link ThreadGroup}. If there is a {@link
     * java.lang.SecurityManager}, it uses the group of {@link
     * System#getSecurityManager}, else the group of the thread
     * invoking this <tt>defaultThreadFactory</tt> method. Each new
     * thread is created as a non-daemon thread with priority
     * <tt>Thread.NORM_PRIORITY</tt>. New threads have names
     * accessible via {@link Thread#getName} of
     * <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
     * number of this factory, and <em>M</em> is the sequence number
     * of the thread created by this factory.
     * @return the thread factory
     */
    public static ThreadFactory defaultThreadFactory() {
        return new DefaultThreadFactory();
    }

    /**
     * Return a thread factory used to create new threads that
     * have the same permissions as the current thread.
     * This factory creates threads with the same settings as {@link
     * Executors#defaultThreadFactory}, additionally setting the
     * AccessControlContext and contextClassLoader of new threads to
     * be the same as the thread invoking this
     * <tt>privilegedThreadFactory</tt> method.  A new
     * <tt>privilegedThreadFactory</tt> can be created within an
     * {@link AccessController#doPrivileged} action setting the
     * current thread's access control context to create threads with
     * the selected permission settings holding within that action.
     *
     * <p> Note that while tasks running within such threads will have
     * the same access control and class loader settings as the
     * current thread, they need not have the same {@link
     * java.lang.ThreadLocal} or {@link
     * java.lang.InheritableThreadLocal} values. If necessary,
     * particular values of thread locals can be set or reset before
     * any task runs in {@link ThreadPoolExecutor} subclasses using
     * {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
     * necessary to initialize worker threads to have the same
     * InheritableThreadLocal settings as some other designated
     * thread, you can create a custom ThreadFactory in which that
     * thread waits for and services requests to create others that
     * will inherit its values.
     *
     * @return the thread factory
     * @throws AccessControlException if the current access control
     * context does not have permission to both get and set context
     * class loader.
     * @see PrivilegedFutureTask
     */
    public static ThreadFactory privilegedThreadFactory() {
        return new PrivilegedThreadFactory();
    }

    static class DefaultThreadFactory implements ThreadFactory {
        static final AtomicInteger poolNumber = new AtomicInteger(1);
        final ThreadGroup group;
        final AtomicInteger threadNumber = new AtomicInteger(1);
        final String namePrefix;

        DefaultThreadFactory() {
            SecurityManager s = System.getSecurityManager();
            group = (s != null)? s.getThreadGroup() :
                                 Thread.currentThread().getThreadGroup();
            namePrefix = "pool-" + 
                          poolNumber.getAndIncrement() + 
                         "-thread-";
        }

        public Thread newThread(Runnable r) {
            Thread t = new Thread(group, r, 
                                  namePrefix + threadNumber.getAndIncrement(),
                                  0);
            if (t.isDaemon())
                t.setDaemon(false);
            if (t.getPriority() != Thread.NORM_PRIORITY)
                t.setPriority(Thread.NORM_PRIORITY);
            return t;
        }
    }

    static class PrivilegedThreadFactory extends DefaultThreadFactory {
        private final ClassLoader ccl;
        private final AccessControlContext acc;

        PrivilegedThreadFactory() {
            super();
            this.ccl = Thread.currentThread().getContextClassLoader();
            this.acc = AccessController.getContext();
            acc.checkPermission(new RuntimePermission("setContextClassLoader"));
        }
        
        public Thread newThread(final Runnable r) {
            return super.newThread(new Runnable() {
                public void run() {
                    AccessController.doPrivileged(new PrivilegedAction() {
                        public Object run() { 
                            Thread.currentThread().setContextClassLoader(ccl);
                            r.run();
                            return null; 
                        }
                    }, acc);
                }
            });
        }
        
    }


   /**
     * A wrapper class that exposes only the ExecutorService methods
     * of an implementation.
     */
    private static class DelegatedExecutorService extends AbstractExecutorService {
        private final ExecutorService e;
        DelegatedExecutorService(ExecutorService executor) { e = executor; }
        public void execute(Runnable command) { e.execute(command); }
        public void shutdown() { e.shutdown(); }
        public List<Runnable> shutdownNow() { return e.shutdownNow(); }
        public boolean isShutdown() { return e.isShutdown(); }
        public boolean isTerminated() { return e.isTerminated(); }
        public boolean awaitTermination(long timeout, TimeUnit unit)
            throws InterruptedException {
            return e.awaitTermination(timeout, unit);
        }
        public <T> Future<T> submit(Runnable task, T result) {
            return e.submit(task, result);
        }
        public <T> Future<T> submit(Callable<T> task) {
            return e.submit(task);
        }

        public void invoke(Runnable task) throws ExecutionException, InterruptedException {
            e.invoke(task);
        }
        public <T> T invoke(Callable<T> task) throws ExecutionException, InterruptedException {
            return e.invoke(task);
        }
        public Future<Object> submit(PrivilegedAction action) {
            return e.submit(action);
        }
        public Future<Object> submit(PrivilegedExceptionAction action) {
            return e.submit(action);
        }
        public  <T> List<Future<T>> invokeAll(Collection<Runnable> tasks, T result)
            throws InterruptedException {
            return e.invokeAll(tasks, result);
        }
        public <T> List<Future<T>> invokeAll(Collection<Runnable> tasks, T result,
                                             long timeout, TimeUnit unit) 
            throws InterruptedException {
            return e.invokeAll(tasks, result, timeout, unit);
        }
        public     <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
            throws InterruptedException {
            return e.invokeAll(tasks);
        }
        public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks, 
                                             long timeout, TimeUnit unit) 
            throws InterruptedException {
            return e.invokeAll(tasks, timeout, unit);
        }
        public <T> T invokeAny(Collection<Callable<T>> tasks)
            throws InterruptedException, ExecutionException {
            return e.invokeAny(tasks);
        }
        public <T> T invokeAny(Collection<Callable<T>> tasks, 
                               long timeout, TimeUnit unit) 
            throws InterruptedException, ExecutionException, TimeoutException {
            return e.invokeAny(tasks, timeout, unit);
        }
        public <T> T invokeAny(Collection<Runnable> tasks, T result)
            throws InterruptedException, ExecutionException {
            return e.invokeAny(tasks, result);
        }
        public <T> T invokeAny(Collection<Runnable> tasks, T result,
                               long timeout, TimeUnit unit) 
            throws InterruptedException, ExecutionException, TimeoutException {
            return e.invokeAny(tasks, result, timeout, unit);
        }
    }
    
    /**
     * A wrapper class that exposes only the ExecutorService and 
     * ScheduleExecutor methods of a ScheduledThreadPoolExecutor.
     */
    private static class DelegatedScheduledExecutorService
            extends DelegatedExecutorService 
            implements ScheduledExecutorService {
        private final ScheduledExecutorService e;
        DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
            super(executor);
            e = executor;
        }
        public ScheduledFuture<?> schedule(Runnable command, long delay,  TimeUnit unit) {
            return e.schedule(command, delay, unit);
        }
        public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
            return e.schedule(callable, delay, unit);
        }
        public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay,  long period, TimeUnit unit) {
            return e.scheduleAtFixedRate(command, initialDelay, period, unit);
        }
        public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay,  long delay, TimeUnit unit) {
            return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
        }
    }

        
    /** Cannot instantiate. */
    private Executors() {}
}
Revision:	1.36
Committed:	Wed Dec 17 17:00:24 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.35:	+146 -10 lines
Log Message:	Export delegation wrappers; fix/add documentation
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain. Use, modify, and
4	* redistribute this code in any way without acknowledgement.
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
15	/**
16	* Factory and utility methods for {@link Executor}, {@link
17	* ExecutorService}, and {@link ThreadFactory} classes defined in this
18	* package.
19	*
20	* @since 1.5
21	* @author Doug Lea
22	*/
23	public class Executors {
24
25	/**
26	* Creates a thread pool that reuses a fixed set of threads
27	* operating off a shared unbounded queue. If any thread
28	* terminates due to a failure during execution prior to shutdown,
29	* a new one will take its place if needed to execute subsequent
30	* tasks.
31	*
32	* @param nThreads the number of threads in the pool
33	* @return the newly created thread pool
34	*/
35	public static ExecutorService newFixedThreadPool(int nThreads) {
36	return new ThreadPoolExecutor(nThreads, nThreads,
37	0L, TimeUnit.MILLISECONDS,
38	new LinkedBlockingQueue<Runnable>());
39	}
40
41	/**
42	* Creates a thread pool that reuses a fixed set of threads
43	* operating off a shared unbounded queue, using the provided
44	* ThreadFactory to create new threads when needed.
45	*
46	* @param nThreads the number of threads in the pool
47	* @param threadFactory the factory to use when creating new threads
48	* @return the newly created thread pool
49	*/
50	public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
51	return new ThreadPoolExecutor(nThreads, nThreads,
52	0L, TimeUnit.MILLISECONDS,
53	new LinkedBlockingQueue<Runnable>(),
54	threadFactory);
55	}
56
57	/**
58	* Creates an Executor that uses a single worker thread operating
59	* off an unbounded queue. (Note however that if this single
60	* thread terminates due to a failure during execution prior to
61	* shutdown, a new one will take its place if needed to execute
62	* subsequent tasks.) Tasks are guaranteed to execute
63	* sequentially, and no more than one task will be active at any
64	* given time. The returned executor cannot be reconfigured
65	* to use additional threads.
66	*
67	* @return the newly-created single-threaded Executor
68	*/
69	public static ExecutorService newSingleThreadExecutor() {
70	return unconfigurableExecutorService
71	(new ThreadPoolExecutor(1, 1,
72	0L, TimeUnit.MILLISECONDS,
73	new LinkedBlockingQueue<Runnable>()));
74	}
75
76	/**
77	* Creates an Executor that uses a single worker thread operating
78	* off an unbounded queue, and uses the provided ThreadFactory to
79	* create a new thread when needed. The returned executor cannot be
80	* reconfigured to use additional threads.
81	* @param threadFactory the factory to use when creating new
82	* threads
83	*
84	* @return the newly-created single-threaded Executor
85	*/
86	public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
87	return unconfigurableExecutorService
88	(new ThreadPoolExecutor(1, 1,
89	0L, TimeUnit.MILLISECONDS,
90	new LinkedBlockingQueue<Runnable>(),
91	threadFactory));
92	}
93
94	/**
95	* Creates a thread pool that creates new threads as needed, but
96	* will reuse previously constructed threads when they are
97	* available. These pools will typically improve the performance
98	* of programs that execute many short-lived asynchronous tasks.
99	* Calls to <tt>execute</tt> will reuse previously constructed
100	* threads if available. If no existing thread is available, a new
101	* thread will be created and added to the pool. Threads that have
102	* not been used for sixty seconds are terminated and removed from
103	* the cache. Thus, a pool that remains idle for long enough will
104	* not consume any resources. Note that pools with similar
105	* properties but different details (for example, timeout parameters)
106	* may be created using {@link ThreadPoolExecutor} constructors.
107	*
108	* @return the newly created thread pool
109	*/
110	public static ExecutorService newCachedThreadPool() {
111	return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
112	60, TimeUnit.SECONDS,
113	new SynchronousQueue<Runnable>());
114	}
115
116	/**
117	* Creates a thread pool that creates new threads as needed, but
118	* will reuse previously constructed threads when they are
119	* available, and uses the provided
120	* ThreadFactory to create new threads when needed.
121	* @param threadFactory the factory to use when creating new threads
122	* @return the newly created thread pool
123	*/
124	public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
125	return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
126	60, TimeUnit.SECONDS,
127	new SynchronousQueue<Runnable>(),
128	threadFactory);
129	}
130
131	/**
132	* Creates a thread pool that can schedule commands to run after a
133	* given delay, or to execute periodically.
134	* @return a newly created scheduled thread pool with termination management
135	*/
136	public static ScheduledExecutorService newScheduledThreadPool() {
137	return newScheduledThreadPool(1);
138	}
139
140	/**
141	* Creates a thread pool that can schedule commands to run after a
142	* given delay, or to execute periodically.
143	* @param corePoolSize the number of threads to keep in the pool,
144	* even if they are idle.
145	* @return a newly created scheduled thread pool with termination management
146	*/
147	public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
148	return new ScheduledThreadPoolExecutor(corePoolSize);
149	}
150
151	/**
152	* Creates a thread pool that can schedule commands to run after a
153	* given delay, or to execute periodically.
154	* @param corePoolSize the number of threads to keep in the pool,
155	* even if they are idle.
156	* @param threadFactory the factory to use when the executor
157	* creates a new thread.
158	* @return a newly created scheduled thread pool with termination management
159	*/
160	public static ScheduledExecutorService newScheduledThreadPool(
161	int corePoolSize, ThreadFactory threadFactory) {
162	return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
163	}
164
165
166	/**
167	* Creates and returns an object that delegates all defined {@link
168	* ExecutorService} methods to the given executor, but not any
169	* other methods that might otherwise be accessible using
170	* casts. This provides a way to safely "freeze" configuration and
171	* disallow tuning of a given concrete implementation.
172	* @param executor the underlying implementation
173	* @return an <tt>ExecutorService</tt> instance
174	* @throws NullPointerException if executor null
175	*/
176	public static ExecutorService unconfigurableExecutorService(ExecutorService executor) {
177	if (executor == null)
178	throw new NullPointerException();
179	return new DelegatedExecutorService(executor);
180	}
181
182	/**
183	* Creates and returns an object that delegates all defined {@link
184	* ScheduledExecutorService} methods to the given executor, but
185	* not any other methods that might otherwise be accessible using
186	* casts. This provides a way to safely "freeze" configuration and
187	* disallow tuning of a given concrete implementation.
188	* @param executor the underlying implementation
189	* @return a <tt>ScheduledExecutorService</tt> instance
190	* @throws NullPointerException if executor null
191	*/
192	public static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor) {
193	if (executor == null)
194	throw new NullPointerException();
195	return new DelegatedScheduledExecutorService(executor);
196	}
197
198	/**
199	* Return a default thread factory used to create new threads.
200	* This factory creates all new threads used by an Executor in the
201	* same {@link ThreadGroup}. If there is a {@link
202	* java.lang.SecurityManager}, it uses the group of {@link
203	* System#getSecurityManager}, else the group of the thread
204	* invoking this <tt>defaultThreadFactory</tt> method. Each new
205	* thread is created as a non-daemon thread with priority
206	* <tt>Thread.NORM_PRIORITY</tt>. New threads have names
207	* accessible via {@link Thread#getName} of
208	* <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
209	* number of this factory, and <em>M</em> is the sequence number
210	* of the thread created by this factory.
211	* @return the thread factory
212	*/
213	public static ThreadFactory defaultThreadFactory() {
214	return new DefaultThreadFactory();
215	}
216
217	/**
218	* Return a thread factory used to create new threads that
219	* have the same permissions as the current thread.
220	* This factory creates threads with the same settings as {@link
221	* Executors#defaultThreadFactory}, additionally setting the
222	* AccessControlContext and contextClassLoader of new threads to
223	* be the same as the thread invoking this
224	* <tt>privilegedThreadFactory</tt> method. A new
225	* <tt>privilegedThreadFactory</tt> can be created within an
226	* {@link AccessController#doPrivileged} action setting the
227	* current thread's access control context to create threads with
228	* the selected permission settings holding within that action.
229	*
230	* <p> Note that while tasks running within such threads will have
231	* the same access control and class loader settings as the
232	* current thread, they need not have the same {@link
233	* java.lang.ThreadLocal} or {@link
234	* java.lang.InheritableThreadLocal} values. If necessary,
235	* particular values of thread locals can be set or reset before
236	* any task runs in {@link ThreadPoolExecutor} subclasses using
237	* {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
238	* necessary to initialize worker threads to have the same
239	* InheritableThreadLocal settings as some other designated
240	* thread, you can create a custom ThreadFactory in which that
241	* thread waits for and services requests to create others that
242	* will inherit its values.
243	*
244	* @return the thread factory
245	* @throws AccessControlException if the current access control
246	* context does not have permission to both get and set context
247	* class loader.
248	* @see PrivilegedFutureTask
249	*/
250	public static ThreadFactory privilegedThreadFactory() {
251	return new PrivilegedThreadFactory();
252	}
253
254	static class DefaultThreadFactory implements ThreadFactory {
255	static final AtomicInteger poolNumber = new AtomicInteger(1);
256	final ThreadGroup group;
257	final AtomicInteger threadNumber = new AtomicInteger(1);
258	final String namePrefix;
259
260	DefaultThreadFactory() {
261	SecurityManager s = System.getSecurityManager();
262	group = (s != null)? s.getThreadGroup() :
263	Thread.currentThread().getThreadGroup();
264	namePrefix = "pool-" +
265	poolNumber.getAndIncrement() +
266	"-thread-";
267	}
268
269	public Thread newThread(Runnable r) {
270	Thread t = new Thread(group, r,
271	namePrefix + threadNumber.getAndIncrement(),
272	0);
273	if (t.isDaemon())
274	t.setDaemon(false);
275	if (t.getPriority() != Thread.NORM_PRIORITY)
276	t.setPriority(Thread.NORM_PRIORITY);
277	return t;
278	}
279	}
280
281	static class PrivilegedThreadFactory extends DefaultThreadFactory {
282	private final ClassLoader ccl;
283	private final AccessControlContext acc;
284
285	PrivilegedThreadFactory() {
286	super();
287	this.ccl = Thread.currentThread().getContextClassLoader();
288	this.acc = AccessController.getContext();
289	acc.checkPermission(new RuntimePermission("setContextClassLoader"));
290	}
291
292	public Thread newThread(final Runnable r) {
293	return super.newThread(new Runnable() {
294	public void run() {
295	AccessController.doPrivileged(new PrivilegedAction() {
296	public Object run() {
297	Thread.currentThread().setContextClassLoader(ccl);
298	r.run();
299	return null;
300	}
301	}, acc);
302	}
303	});
304	}
305
306	}
307
308
309	/**
310	* A wrapper class that exposes only the ExecutorService methods
311	* of an implementation.
312	*/
313	private static class DelegatedExecutorService extends AbstractExecutorService {
314	private final ExecutorService e;
315	DelegatedExecutorService(ExecutorService executor) { e = executor; }
316	public void execute(Runnable command) { e.execute(command); }
317	public void shutdown() { e.shutdown(); }
318	public List<Runnable> shutdownNow() { return e.shutdownNow(); }
319	public boolean isShutdown() { return e.isShutdown(); }
320	public boolean isTerminated() { return e.isTerminated(); }
321	public boolean awaitTermination(long timeout, TimeUnit unit)
322	throws InterruptedException {
323	return e.awaitTermination(timeout, unit);
324	}
325	public <T> Future<T> submit(Runnable task, T result) {
326	return e.submit(task, result);
327	}
328	public <T> Future<T> submit(Callable<T> task) {
329	return e.submit(task);
330	}
331
332	public void invoke(Runnable task) throws ExecutionException, InterruptedException {
333	e.invoke(task);
334	}
335	public <T> T invoke(Callable<T> task) throws ExecutionException, InterruptedException {
336	return e.invoke(task);
337	}
338	public Future<Object> submit(PrivilegedAction action) {
339	return e.submit(action);
340	}
341	public Future<Object> submit(PrivilegedExceptionAction action) {
342	return e.submit(action);
343	}
344	public <T> List<Future<T>> invokeAll(Collection<Runnable> tasks, T result)
345	throws InterruptedException {
346	return e.invokeAll(tasks, result);
347	}
348	public <T> List<Future<T>> invokeAll(Collection<Runnable> tasks, T result,
349	long timeout, TimeUnit unit)
350	throws InterruptedException {
351	return e.invokeAll(tasks, result, timeout, unit);
352	}
353	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
354	throws InterruptedException {
355	return e.invokeAll(tasks);
356	}
357	public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
358	long timeout, TimeUnit unit)
359	throws InterruptedException {
360	return e.invokeAll(tasks, timeout, unit);
361	}
362	public <T> T invokeAny(Collection<Callable<T>> tasks)
363	throws InterruptedException, ExecutionException {
364	return e.invokeAny(tasks);
365	}
366	public <T> T invokeAny(Collection<Callable<T>> tasks,
367	long timeout, TimeUnit unit)
368	throws InterruptedException, ExecutionException, TimeoutException {
369	return e.invokeAny(tasks, timeout, unit);
370	}
371	public <T> T invokeAny(Collection<Runnable> tasks, T result)
372	throws InterruptedException, ExecutionException {
373	return e.invokeAny(tasks, result);
374	}
375	public <T> T invokeAny(Collection<Runnable> tasks, T result,
376	long timeout, TimeUnit unit)
377	throws InterruptedException, ExecutionException, TimeoutException {
378	return e.invokeAny(tasks, result, timeout, unit);
379	}
380	}
381
382	/**
383	* A wrapper class that exposes only the ExecutorService and
384	* ScheduleExecutor methods of a ScheduledThreadPoolExecutor.
385	*/
386	private static class DelegatedScheduledExecutorService
387	extends DelegatedExecutorService
388	implements ScheduledExecutorService {
389	private final ScheduledExecutorService e;
390	DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
391	super(executor);
392	e = executor;
393	}
394	public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
395	return e.schedule(command, delay, unit);
396	}
397	public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
398	return e.schedule(callable, delay, unit);
399	}
400	public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
401	return e.scheduleAtFixedRate(command, initialDelay, period, unit);
402	}
403	public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
404	return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
405	}
406	}
407
408
409	/** Cannot instantiate. */
410	private Executors() {}
411	}