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}, {@link ThreadFactory}, and {@link Future}
 * classes defined in this package.
 *
 * @since 1.5
 * @author Doug Lea
 */
public class Executors {

    /**
     * A wrapper class that exposes only the ExecutorService methods
     * of an implementation.
     */
    private static class DelegatedExecutorService implements ExecutorService {
        private final ExecutorService e;
        DelegatedExecutorService(ExecutorService executor) { e = executor; }
        public void execute(Runnable command) { e.execute(command); }
        public void shutdown() { e.shutdown(); }
        public List 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);
        }
    }
    
    /**
     * A wrapper class that exposes only the ExecutorService and 
     * ScheduleExecutor methods of a ScheduledThreadPoolExecutor.
     */
    private static class DelegatedScheduledExecutorService
            extends DelegatedExecutorService 
            implements ScheduledExecutorService {
        private final ScheduledExecutor e;
        DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
            super(executor);
            e = executor;
        }
        public ScheduledFuture<Boolean> 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<Boolean> scheduleAtFixedRate(Runnable command, long initialDelay,  long period, TimeUnit unit) {
            return e.scheduleAtFixedRate(command, initialDelay, period, unit);
        }
        public ScheduledFuture<Boolean> scheduleWithFixedDelay(Runnable command, long initialDelay,  long delay, TimeUnit unit) {
            return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
        }
    }

    /**
     * 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 DelegatedExecutorService
            (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 DelegatedExecutorService
            (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. This method is equivalent in effect to
     *<tt>new FixedThreadPool(1)</tt>.
     *
     * @return the newly-created single-threaded Executor
     */
    public static ExecutorService newSingleThreadExecutor() {
        return new DelegatedExecutorService
            (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 new threads when needed.
     * @param threadFactory the factory to use when creating new
     * threads
     *
     * @return the newly-created single-threaded Executor
     */
    public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
        return new DelegatedExecutorService
            (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 DelegatedExecutorService
            (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 DelegatedExecutorService
            (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 <tt>ScheduledExecutor</tt> that may safely be cast to
     * an <tt>ExecutorService</tt>.
     */
    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 <tt>ScheduledExecutor</tt> that may safely be cast to
     * an <tt>ExecutorService</tt>.
     */
    public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
        return new DelegatedScheduledExecutorService
            (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 <tt>ScheduledExecutor</tt> that may safely be cast to
     * an <tt>ExecutorService</tt>.
     */
    public static ScheduledExecutorService newScheduledThreadPool(
            int corePoolSize, ThreadFactory threadFactory) {
        return new DelegatedScheduledExecutorService
            (new ScheduledThreadPoolExecutor(corePoolSize, threadFactory));
    }

    /**
     * Executes a Runnable task and returns a Future representing that
     * task.
     *
     * @param executor the Executor to which the task will be submitted
     * @param task the task to submit
     * @return a Future representing pending completion of the task,
     * and whose <tt>get()</tt> method will return <tt>Boolean.TRUE</tt>
     * upon completion
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     */
    public static Future<Boolean> execute(Executor executor, Runnable task) {
        FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
        executor.execute(ftask);
        return ftask;
    }

    /**
     * Executes a Runnable task and returns a Future representing that
     * task.
     *
     * @param executor the Executor to which the task will be submitted
     * @param task the task to submit
     * @param value the value which will become the return value of
     * the task upon task completion
     * @return a Future representing pending completion of the task
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     */
    public static <T> Future<T> execute(Executor executor, Runnable task, T value) {
        FutureTask<T> ftask = new FutureTask<T>(task, value);
        executor.execute(ftask);
        return ftask;
    }

    /**
     * Executes a value-returning task and returns a Future
     * representing the pending results of the task.
     *
     * @param executor the Executor to which the task will be submitted
     * @param task the task to submit
     * @return a Future representing pending completion of the task
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     */
    public static <T> Future<T> execute(Executor executor, Callable<T> task) {
        FutureTask<T> ftask = new FutureTask<T>(task);
        executor.execute(ftask);
        return ftask;
    }

    /**
     * Executes a Runnable task and blocks until it completes normally
     * or throws an exception.
     *
     * @param executor the Executor to which the task will be submitted
     * @param task the task to submit
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     * @throws ExecutionException if the task encountered an exception
     * while executing
     */
    public static void invoke(Executor executor, Runnable task)
            throws ExecutionException, InterruptedException {
        FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
        executor.execute(ftask);
        ftask.get();
    }

    /**
     * Executes a value-returning task and blocks until it returns a
     * value or throws an exception.
     *
     * @param executor the Executor to which the task will be submitted
     * @param task the task to submit
     * @return a Future representing pending completion of the task
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     * @throws InterruptedException if interrupted while waiting for
     * completion
     * @throws ExecutionException if the task encountered an exception
     * while executing
     */
    public static <T> T invoke(Executor executor, Callable<T> task)
            throws ExecutionException, InterruptedException {
        FutureTask<T> ftask = new FutureTask<T>(task);
        executor.execute(ftask);
        return ftask.get();
    }


    /**
     * Executes a privileged action under the current access control 
     * context and returns a Future representing the pending result 
     * object of that action.
     *
     * @param executor the Executor to which the task will be submitted
     * @param action the action to submit
     * @return a Future representing pending completion of the action
     * @throws RejectedExecutionException if action cannot be scheduled
     * for execution
     */
    public static Future<Object> execute(Executor executor, PrivilegedAction action) {
        Callable<Object> task = new PrivilegedActionAdapter(action);
        FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
        executor.execute(future);
        return future;
    }

    /**
     * Executes a privileged exception action under the current access control 
     * context and returns a Future representing the pending result 
     * object of that action.
     *
     * @param executor the Executor to which the task will be submitted
     * @param action the action to submit
     * @return a Future representing pending completion of the action
     * @throws RejectedExecutionException if action cannot be scheduled
     * for execution
     */
    public static Future<Object> execute(Executor executor, PrivilegedExceptionAction action) {
        Callable<Object> task = new PrivilegedExceptionActionAdapter(action);
        FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
        executor.execute(future);
        return future;
    }

    private static class PrivilegedActionAdapter implements Callable<Object> {
        PrivilegedActionAdapter(PrivilegedAction action) {
            this.action = action;
        }
        public Object call () {
            return action.run();
        }
        private final PrivilegedAction action;
    }
    
    private static class PrivilegedExceptionActionAdapter implements Callable<Object> {
        PrivilegedExceptionActionAdapter(PrivilegedExceptionAction action) {
            this.action = action;
        }
        public Object call () throws Exception {
            return action.run();
        }
        private final PrivilegedExceptionAction action;
    }
        
    /**
     * 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);
                }
            });
        }
        
    }

        
    /** Cannot instantiate. */
    private Executors() {}
}
Revision:	1.28
Committed:	Sun Dec 7 14:57:46 2003 UTC (20 years, 6 months ago) by tim
Branch:	MAIN
Changes since 1.27:	+7 -6 lines
Log Message:	ScheduledExecutorService for Executors factory method return type
#	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}, {@link ThreadFactory}, and {@link Future}
18	* classes defined in this package.
19	*
20	* @since 1.5
21	* @author Doug Lea
22	*/
23	public class Executors {
24
25	/**
26	* A wrapper class that exposes only the ExecutorService methods
27	* of an implementation.
28	*/
29	private static class DelegatedExecutorService implements ExecutorService {
30	private final ExecutorService e;
31	DelegatedExecutorService(ExecutorService executor) { e = executor; }
32	public void execute(Runnable command) { e.execute(command); }
33	public void shutdown() { e.shutdown(); }
34	public List shutdownNow() { return e.shutdownNow(); }
35	public boolean isShutdown() { return e.isShutdown(); }
36	public boolean isTerminated() { return e.isTerminated(); }
37	public boolean awaitTermination(long timeout, TimeUnit unit)
38	throws InterruptedException {
39	return e.awaitTermination(timeout, unit);
40	}
41	}
42
43	/**
44	* A wrapper class that exposes only the ExecutorService and
45	* ScheduleExecutor methods of a ScheduledThreadPoolExecutor.
46	*/
47	private static class DelegatedScheduledExecutorService
48	extends DelegatedExecutorService
49	implements ScheduledExecutorService {
50	private final ScheduledExecutor e;
51	DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
52	super(executor);
53	e = executor;
54	}
55	public ScheduledFuture<Boolean> schedule(Runnable command, long delay, TimeUnit unit) {
56	return e.schedule(command, delay, unit);
57	}
58	public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
59	return e.schedule(callable, delay, unit);
60	}
61	public ScheduledFuture<Boolean> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
62	return e.scheduleAtFixedRate(command, initialDelay, period, unit);
63	}
64	public ScheduledFuture<Boolean> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
65	return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
66	}
67	}
68
69	/**
70	* Creates a thread pool that reuses a fixed set of threads
71	* operating off a shared unbounded queue. If any thread
72	* terminates due to a failure during execution prior to shutdown,
73	* a new one will take its place if needed to execute subsequent
74	* tasks.
75	*
76	* @param nThreads the number of threads in the pool
77	* @return the newly created thread pool
78	*/
79	public static ExecutorService newFixedThreadPool(int nThreads) {
80	return new DelegatedExecutorService
81	(new ThreadPoolExecutor(nThreads, nThreads,
82	0L, TimeUnit.MILLISECONDS,
83	new LinkedBlockingQueue<Runnable>()));
84	}
85
86	/**
87	* Creates a thread pool that reuses a fixed set of threads
88	* operating off a shared unbounded queue, using the provided
89	* ThreadFactory to create new threads when needed.
90	*
91	* @param nThreads the number of threads in the pool
92	* @param threadFactory the factory to use when creating new threads
93	* @return the newly created thread pool
94	*/
95	public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
96	return new DelegatedExecutorService
97	(new ThreadPoolExecutor(nThreads, nThreads,
98	0L, TimeUnit.MILLISECONDS,
99	new LinkedBlockingQueue<Runnable>(),
100	threadFactory));
101	}
102
103	/**
104	* Creates an Executor that uses a single worker thread operating
105	* off an unbounded queue. (Note however that if this single
106	* thread terminates due to a failure during execution prior to
107	* shutdown, a new one will take its place if needed to execute
108	* subsequent tasks.) Tasks are guaranteed to execute
109	* sequentially, and no more than one task will be active at any
110	* given time. This method is equivalent in effect to
111	*<tt>new FixedThreadPool(1)</tt>.
112	*
113	* @return the newly-created single-threaded Executor
114	*/
115	public static ExecutorService newSingleThreadExecutor() {
116	return new DelegatedExecutorService
117	(new ThreadPoolExecutor(1, 1,
118	0L, TimeUnit.MILLISECONDS,
119	new LinkedBlockingQueue<Runnable>()));
120	}
121
122	/**
123	* Creates an Executor that uses a single worker thread operating
124	* off an unbounded queue, and uses the provided ThreadFactory to
125	* create new threads when needed.
126	* @param threadFactory the factory to use when creating new
127	* threads
128	*
129	* @return the newly-created single-threaded Executor
130	*/
131	public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
132	return new DelegatedExecutorService
133	(new ThreadPoolExecutor(1, 1,
134	0L, TimeUnit.MILLISECONDS,
135	new LinkedBlockingQueue<Runnable>(),
136	threadFactory));
137	}
138
139	/**
140	* Creates a thread pool that creates new threads as needed, but
141	* will reuse previously constructed threads when they are
142	* available. These pools will typically improve the performance
143	* of programs that execute many short-lived asynchronous tasks.
144	* Calls to <tt>execute</tt> will reuse previously constructed
145	* threads if available. If no existing thread is available, a new
146	* thread will be created and added to the pool. Threads that have
147	* not been used for sixty seconds are terminated and removed from
148	* the cache. Thus, a pool that remains idle for long enough will
149	* not consume any resources. Note that pools with similar
150	* properties but different details (for example, timeout parameters)
151	* may be created using {@link ThreadPoolExecutor} constructors.
152	*
153	* @return the newly created thread pool
154	*/
155	public static ExecutorService newCachedThreadPool() {
156	return new DelegatedExecutorService
157	(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
158	60, TimeUnit.SECONDS,
159	new SynchronousQueue<Runnable>()));
160	}
161
162	/**
163	* Creates a thread pool that creates new threads as needed, but
164	* will reuse previously constructed threads when they are
165	* available, and uses the provided
166	* ThreadFactory to create new threads when needed.
167	* @param threadFactory the factory to use when creating new threads
168	* @return the newly created thread pool
169	*/
170	public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
171	return new DelegatedExecutorService
172	(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
173	60, TimeUnit.SECONDS,
174	new SynchronousQueue<Runnable>(),
175	threadFactory));
176	}
177
178	/**
179	* Creates a thread pool that can schedule commands to run after a
180	* given delay, or to execute periodically.
181	* @return a <tt>ScheduledExecutor</tt> that may safely be cast to
182	* an <tt>ExecutorService</tt>.
183	*/
184	public static ScheduledExecutorService newScheduledThreadPool() {
185	return newScheduledThreadPool(1);
186	}
187
188	/**
189	* Creates a thread pool that can schedule commands to run after a
190	* given delay, or to execute periodically.
191	* @param corePoolSize the number of threads to keep in the pool,
192	* even if they are idle.
193	* @return a <tt>ScheduledExecutor</tt> that may safely be cast to
194	* an <tt>ExecutorService</tt>.
195	*/
196	public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
197	return new DelegatedScheduledExecutorService
198	(new ScheduledThreadPoolExecutor(corePoolSize));
199	}
200
201	/**
202	* Creates a thread pool that can schedule commands to run after a
203	* given delay, or to execute periodically.
204	* @param corePoolSize the number of threads to keep in the pool,
205	* even if they are idle.
206	* @param threadFactory the factory to use when the executor
207	* creates a new thread.
208	* @return a <tt>ScheduledExecutor</tt> that may safely be cast to
209	* an <tt>ExecutorService</tt>.
210	*/
211	public static ScheduledExecutorService newScheduledThreadPool(
212	int corePoolSize, ThreadFactory threadFactory) {
213	return new DelegatedScheduledExecutorService
214	(new ScheduledThreadPoolExecutor(corePoolSize, threadFactory));
215	}
216
217	/**
218	* Executes a Runnable task and returns a Future representing that
219	* task.
220	*
221	* @param executor the Executor to which the task will be submitted
222	* @param task the task to submit
223	* @return a Future representing pending completion of the task,
224	* and whose <tt>get()</tt> method will return <tt>Boolean.TRUE</tt>
225	* upon completion
226	* @throws RejectedExecutionException if task cannot be scheduled
227	* for execution
228	*/
229	public static Future<Boolean> execute(Executor executor, Runnable task) {
230	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
231	executor.execute(ftask);
232	return ftask;
233	}
234
235	/**
236	* Executes a Runnable task and returns a Future representing that
237	* task.
238	*
239	* @param executor the Executor to which the task will be submitted
240	* @param task the task to submit
241	* @param value the value which will become the return value of
242	* the task upon task completion
243	* @return a Future representing pending completion of the task
244	* @throws RejectedExecutionException if task cannot be scheduled
245	* for execution
246	*/
247	public static <T> Future<T> execute(Executor executor, Runnable task, T value) {
248	FutureTask<T> ftask = new FutureTask<T>(task, value);
249	executor.execute(ftask);
250	return ftask;
251	}
252
253	/**
254	* Executes a value-returning task and returns a Future
255	* representing the pending results of the task.
256	*
257	* @param executor the Executor to which the task will be submitted
258	* @param task the task to submit
259	* @return a Future representing pending completion of the task
260	* @throws RejectedExecutionException if task cannot be scheduled
261	* for execution
262	*/
263	public static <T> Future<T> execute(Executor executor, Callable<T> task) {
264	FutureTask<T> ftask = new FutureTask<T>(task);
265	executor.execute(ftask);
266	return ftask;
267	}
268
269	/**
270	* Executes a Runnable task and blocks until it completes normally
271	* or throws an exception.
272	*
273	* @param executor the Executor to which the task will be submitted
274	* @param task the task to submit
275	* @throws RejectedExecutionException if task cannot be scheduled
276	* for execution
277	* @throws ExecutionException if the task encountered an exception
278	* while executing
279	*/
280	public static void invoke(Executor executor, Runnable task)
281	throws ExecutionException, InterruptedException {
282	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
283	executor.execute(ftask);
284	ftask.get();
285	}
286
287	/**
288	* Executes a value-returning task and blocks until it returns a
289	* value or throws an exception.
290	*
291	* @param executor the Executor to which the task will be submitted
292	* @param task the task to submit
293	* @return a Future representing pending completion of the task
294	* @throws RejectedExecutionException if task cannot be scheduled
295	* for execution
296	* @throws InterruptedException if interrupted while waiting for
297	* completion
298	* @throws ExecutionException if the task encountered an exception
299	* while executing
300	*/
301	public static <T> T invoke(Executor executor, Callable<T> task)
302	throws ExecutionException, InterruptedException {
303	FutureTask<T> ftask = new FutureTask<T>(task);
304	executor.execute(ftask);
305	return ftask.get();
306	}
307
308
309	/**
310	* Executes a privileged action under the current access control
311	* context and returns a Future representing the pending result
312	* object of that action.
313	*
314	* @param executor the Executor to which the task will be submitted
315	* @param action the action to submit
316	* @return a Future representing pending completion of the action
317	* @throws RejectedExecutionException if action cannot be scheduled
318	* for execution
319	*/
320	public static Future<Object> execute(Executor executor, PrivilegedAction action) {
321	Callable<Object> task = new PrivilegedActionAdapter(action);
322	FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
323	executor.execute(future);
324	return future;
325	}
326
327	/**
328	* Executes a privileged exception action under the current access control
329	* context and returns a Future representing the pending result
330	* object of that action.
331	*
332	* @param executor the Executor to which the task will be submitted
333	* @param action the action to submit
334	* @return a Future representing pending completion of the action
335	* @throws RejectedExecutionException if action cannot be scheduled
336	* for execution
337	*/
338	public static Future<Object> execute(Executor executor, PrivilegedExceptionAction action) {
339	Callable<Object> task = new PrivilegedExceptionActionAdapter(action);
340	FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
341	executor.execute(future);
342	return future;
343	}
344
345	private static class PrivilegedActionAdapter implements Callable<Object> {
346	PrivilegedActionAdapter(PrivilegedAction action) {
347	this.action = action;
348	}
349	public Object call () {
350	return action.run();
351	}
352	private final PrivilegedAction action;
353	}
354
355	private static class PrivilegedExceptionActionAdapter implements Callable<Object> {
356	PrivilegedExceptionActionAdapter(PrivilegedExceptionAction action) {
357	this.action = action;
358	}
359	public Object call () throws Exception {
360	return action.run();
361	}
362	private final PrivilegedExceptionAction action;
363	}
364
365	/**
366	* Return a default thread factory used to create new threads.
367	* This factory creates all new threads used by an Executor in the
368	* same {@link ThreadGroup}. If there is a {@link
369	* java.lang.SecurityManager}, it uses the group of {@link
370	* System#getSecurityManager}, else the group of the thread
371	* invoking this <tt>defaultThreadFactory</tt> method. Each new
372	* thread is created as a non-daemon thread with priority
373	* <tt>Thread.NORM_PRIORITY</tt>. New threads have names
374	* accessible via {@link Thread#getName} of
375	* <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
376	* number of this factory, and <em>M</em> is the sequence number
377	* of the thread created by this factory.
378	* @return the thread factory
379	*/
380	public static ThreadFactory defaultThreadFactory() {
381	return new DefaultThreadFactory();
382	}
383
384	/**
385	* Return a thread factory used to create new threads that
386	* have the same permissions as the current thread.
387	* This factory creates threads with the same settings as {@link
388	* Executors#defaultThreadFactory}, additionally setting the
389	* AccessControlContext and contextClassLoader of new threads to
390	* be the same as the thread invoking this
391	* <tt>privilegedThreadFactory</tt> method. A new
392	* <tt>privilegedThreadFactory</tt> can be created within an
393	* {@link AccessController#doPrivileged} action setting the
394	* current thread's access control context to create threads with
395	* the selected permission settings holding within that action.
396	*
397	* <p> Note that while tasks running within such threads will have
398	* the same access control and class loader settings as the
399	* current thread, they need not have the same {@link
400	* java.lang.ThreadLocal} or {@link
401	* java.lang.InheritableThreadLocal} values. If necessary,
402	* particular values of thread locals can be set or reset before
403	* any task runs in {@link ThreadPoolExecutor} subclasses using
404	* {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
405	* necessary to initialize worker threads to have the same
406	* InheritableThreadLocal settings as some other designated
407	* thread, you can create a custom ThreadFactory in which that
408	* thread waits for and services requests to create others that
409	* will inherit its values.
410	*
411	* @return the thread factory
412	* @throws AccessControlException if the current access control
413	* context does not have permission to both get and set context
414	* class loader.
415	* @see PrivilegedFutureTask
416	*/
417	public static ThreadFactory privilegedThreadFactory() {
418	return new PrivilegedThreadFactory();
419	}
420
421	static class DefaultThreadFactory implements ThreadFactory {
422	static final AtomicInteger poolNumber = new AtomicInteger(1);
423	final ThreadGroup group;
424	final AtomicInteger threadNumber = new AtomicInteger(1);
425	final String namePrefix;
426
427	DefaultThreadFactory() {
428	SecurityManager s = System.getSecurityManager();
429	group = (s != null)? s.getThreadGroup() :
430	Thread.currentThread().getThreadGroup();
431	namePrefix = "pool-" +
432	poolNumber.getAndIncrement() +
433	"-thread-";
434	}
435
436	public Thread newThread(Runnable r) {
437	Thread t = new Thread(group, r,
438	namePrefix + threadNumber.getAndIncrement(),
439	0);
440	if (t.isDaemon())
441	t.setDaemon(false);
442	if (t.getPriority() != Thread.NORM_PRIORITY)
443	t.setPriority(Thread.NORM_PRIORITY);
444	return t;
445	}
446	}
447
448	static class PrivilegedThreadFactory extends DefaultThreadFactory {
449	private final ClassLoader ccl;
450	private final AccessControlContext acc;
451
452	PrivilegedThreadFactory() {
453	super();
454	this.ccl = Thread.currentThread().getContextClassLoader();
455	this.acc = AccessController.getContext();
456	acc.checkPermission(new RuntimePermission("setContextClassLoader"));
457	}
458
459	public Thread newThread(final Runnable r) {
460	return super.newThread(new Runnable() {
461	public void run() {
462	AccessController.doPrivileged(new PrivilegedAction() {
463	public Object run() {
464	Thread.currentThread().setContextClassLoader(ccl);
465	r.run();
466	return null;
467	}
468	}, acc);
469	}
470	});
471	}
472
473	}
474
475
476	/** Cannot instantiate. */
477	private Executors() {}
478	}