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 ScheduledExecutor {
        private final ScheduledExecutor e;
        DelegatedScheduledExecutorService(ScheduledThreadPoolExecutor 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 ScheduledExecutor 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 ScheduledExecutor 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 ScheduledExecutor 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:	1.27
Committed:	Sat Dec 6 04:31:03 2003 UTC (20 years, 6 months ago) by tim
Branch:	MAIN
Changes since 1.26:	+8 -48 lines
Log Message:	Removed one of the newScheduledThreadPool factory methods
#	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 implements ScheduledExecutor {
49	private final ScheduledExecutor e;
50	DelegatedScheduledExecutorService(ScheduledThreadPoolExecutor executor) {
51	super(executor);
52	e = executor;
53	}
54	public ScheduledFuture<Boolean> schedule(Runnable command, long delay, TimeUnit unit) {
55	return e.schedule(command, delay, unit);
56	}
57	public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
58	return e.schedule(callable, delay, unit);
59	}
60	public ScheduledFuture<Boolean> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
61	return e.scheduleAtFixedRate(command, initialDelay, period, unit);
62	}
63	public ScheduledFuture<Boolean> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
64	return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
65	}
66	}
67
68	/**
69	* Creates a thread pool that reuses a fixed set of threads
70	* operating off a shared unbounded queue. If any thread
71	* terminates due to a failure during execution prior to shutdown,
72	* a new one will take its place if needed to execute subsequent
73	* tasks.
74	*
75	* @param nThreads the number of threads in the pool
76	* @return the newly created thread pool
77	*/
78	public static ExecutorService newFixedThreadPool(int nThreads) {
79	return new DelegatedExecutorService
80	(new ThreadPoolExecutor(nThreads, nThreads,
81	0L, TimeUnit.MILLISECONDS,
82	new LinkedBlockingQueue<Runnable>()));
83	}
84
85	/**
86	* Creates a thread pool that reuses a fixed set of threads
87	* operating off a shared unbounded queue, using the provided
88	* ThreadFactory to create new threads when needed.
89	*
90	* @param nThreads the number of threads in the pool
91	* @param threadFactory the factory to use when creating new threads
92	* @return the newly created thread pool
93	*/
94	public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
95	return new DelegatedExecutorService
96	(new ThreadPoolExecutor(nThreads, nThreads,
97	0L, TimeUnit.MILLISECONDS,
98	new LinkedBlockingQueue<Runnable>(),
99	threadFactory));
100	}
101
102	/**
103	* Creates an Executor that uses a single worker thread operating
104	* off an unbounded queue. (Note however that if this single
105	* thread terminates due to a failure during execution prior to
106	* shutdown, a new one will take its place if needed to execute
107	* subsequent tasks.) Tasks are guaranteed to execute
108	* sequentially, and no more than one task will be active at any
109	* given time. This method is equivalent in effect to
110	*<tt>new FixedThreadPool(1)</tt>.
111	*
112	* @return the newly-created single-threaded Executor
113	*/
114	public static ExecutorService newSingleThreadExecutor() {
115	return new DelegatedExecutorService
116	(new ThreadPoolExecutor(1, 1,
117	0L, TimeUnit.MILLISECONDS,
118	new LinkedBlockingQueue<Runnable>()));
119	}
120
121	/**
122	* Creates an Executor that uses a single worker thread operating
123	* off an unbounded queue, and uses the provided ThreadFactory to
124	* create new threads when needed.
125	* @param threadFactory the factory to use when creating new
126	* threads
127	*
128	* @return the newly-created single-threaded Executor
129	*/
130	public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
131	return new DelegatedExecutorService
132	(new ThreadPoolExecutor(1, 1,
133	0L, TimeUnit.MILLISECONDS,
134	new LinkedBlockingQueue<Runnable>(),
135	threadFactory));
136	}
137
138	/**
139	* Creates a thread pool that creates new threads as needed, but
140	* will reuse previously constructed threads when they are
141	* available. These pools will typically improve the performance
142	* of programs that execute many short-lived asynchronous tasks.
143	* Calls to <tt>execute</tt> will reuse previously constructed
144	* threads if available. If no existing thread is available, a new
145	* thread will be created and added to the pool. Threads that have
146	* not been used for sixty seconds are terminated and removed from
147	* the cache. Thus, a pool that remains idle for long enough will
148	* not consume any resources. Note that pools with similar
149	* properties but different details (for example, timeout parameters)
150	* may be created using {@link ThreadPoolExecutor} constructors.
151	*
152	* @return the newly created thread pool
153	*/
154	public static ExecutorService newCachedThreadPool() {
155	return new DelegatedExecutorService
156	(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
157	60, TimeUnit.SECONDS,
158	new SynchronousQueue<Runnable>()));
159	}
160
161	/**
162	* Creates a thread pool that creates new threads as needed, but
163	* will reuse previously constructed threads when they are
164	* available, and uses the provided
165	* ThreadFactory to create new threads when needed.
166	* @param threadFactory the factory to use when creating new threads
167	* @return the newly created thread pool
168	*/
169	public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
170	return new DelegatedExecutorService
171	(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
172	60, TimeUnit.SECONDS,
173	new SynchronousQueue<Runnable>(),
174	threadFactory));
175	}
176
177	/**
178	* Creates a thread pool that can schedule commands to run after a
179	* given delay, or to execute periodically.
180	* @return a <tt>ScheduledExecutor</tt> that may safely be cast to
181	* an <tt>ExecutorService</tt>.
182	*/
183	public static ScheduledExecutor newScheduledThreadPool() {
184	return newScheduledThreadPool(1);
185	}
186
187	/**
188	* Creates a thread pool that can schedule commands to run after a
189	* given delay, or to execute periodically.
190	* @param corePoolSize the number of threads to keep in the pool,
191	* even if they are idle.
192	* @return a <tt>ScheduledExecutor</tt> that may safely be cast to
193	* an <tt>ExecutorService</tt>.
194	*/
195	public static ScheduledExecutor newScheduledThreadPool(int corePoolSize) {
196	return new DelegatedScheduledExecutorService
197	(new ScheduledThreadPoolExecutor(corePoolSize));
198	}
199
200	/**
201	* Creates a thread pool that can schedule commands to run after a
202	* given delay, or to execute periodically.
203	* @param corePoolSize the number of threads to keep in the pool,
204	* even if they are idle.
205	* @param threadFactory the factory to use when the executor
206	* creates a new thread.
207	* @return a <tt>ScheduledExecutor</tt> that may safely be cast to
208	* an <tt>ExecutorService</tt>.
209	*/
210	public static ScheduledExecutor newScheduledThreadPool(int corePoolSize,
211	ThreadFactory threadFactory) {
212	return new DelegatedScheduledExecutorService
213	(new ScheduledThreadPoolExecutor(corePoolSize, threadFactory));
214	}
215
216	/**
217	* Executes a Runnable task and returns a Future representing that
218	* task.
219	*
220	* @param executor the Executor to which the task will be submitted
221	* @param task the task to submit
222	* @return a Future representing pending completion of the task,
223	* and whose <tt>get()</tt> method will return <tt>Boolean.TRUE</tt>
224	* upon completion
225	* @throws RejectedExecutionException if task cannot be scheduled
226	* for execution
227	*/
228	public static Future<Boolean> execute(Executor executor, Runnable task) {
229	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
230	executor.execute(ftask);
231	return ftask;
232	}
233
234	/**
235	* Executes a Runnable task and returns a Future representing that
236	* task.
237	*
238	* @param executor the Executor to which the task will be submitted
239	* @param task the task to submit
240	* @param value the value which will become the return value of
241	* the task upon task completion
242	* @return a Future representing pending completion of the task
243	* @throws RejectedExecutionException if task cannot be scheduled
244	* for execution
245	*/
246	public static <T> Future<T> execute(Executor executor, Runnable task, T value) {
247	FutureTask<T> ftask = new FutureTask<T>(task, value);
248	executor.execute(ftask);
249	return ftask;
250	}
251
252	/**
253	* Executes a value-returning task and returns a Future
254	* representing the pending results of the task.
255	*
256	* @param executor the Executor to which the task will be submitted
257	* @param task the task to submit
258	* @return a Future representing pending completion of the task
259	* @throws RejectedExecutionException if task cannot be scheduled
260	* for execution
261	*/
262	public static <T> Future<T> execute(Executor executor, Callable<T> task) {
263	FutureTask<T> ftask = new FutureTask<T>(task);
264	executor.execute(ftask);
265	return ftask;
266	}
267
268	/**
269	* Executes a Runnable task and blocks until it completes normally
270	* or throws an exception.
271	*
272	* @param executor the Executor to which the task will be submitted
273	* @param task the task to submit
274	* @throws RejectedExecutionException if task cannot be scheduled
275	* for execution
276	* @throws ExecutionException if the task encountered an exception
277	* while executing
278	*/
279	public static void invoke(Executor executor, Runnable task)
280	throws ExecutionException, InterruptedException {
281	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
282	executor.execute(ftask);
283	ftask.get();
284	}
285
286	/**
287	* Executes a value-returning task and blocks until it returns a
288	* value or throws an exception.
289	*
290	* @param executor the Executor to which the task will be submitted
291	* @param task the task to submit
292	* @return a Future representing pending completion of the task
293	* @throws RejectedExecutionException if task cannot be scheduled
294	* for execution
295	* @throws InterruptedException if interrupted while waiting for
296	* completion
297	* @throws ExecutionException if the task encountered an exception
298	* while executing
299	*/
300	public static <T> T invoke(Executor executor, Callable<T> task)
301	throws ExecutionException, InterruptedException {
302	FutureTask<T> ftask = new FutureTask<T>(task);
303	executor.execute(ftask);
304	return ftask.get();
305	}
306
307
308	/**
309	* Executes a privileged action under the current access control
310	* context and returns a Future representing the pending result
311	* object of that action.
312	*
313	* @param executor the Executor to which the task will be submitted
314	* @param action the action to submit
315	* @return a Future representing pending completion of the action
316	* @throws RejectedExecutionException if action cannot be scheduled
317	* for execution
318	*/
319	public static Future<Object> execute(Executor executor, PrivilegedAction action) {
320	Callable<Object> task = new PrivilegedActionAdapter(action);
321	FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
322	executor.execute(future);
323	return future;
324	}
325
326	/**
327	* Executes a privileged exception action under the current access control
328	* context and returns a Future representing the pending result
329	* object of that action.
330	*
331	* @param executor the Executor to which the task will be submitted
332	* @param action the action to submit
333	* @return a Future representing pending completion of the action
334	* @throws RejectedExecutionException if action cannot be scheduled
335	* for execution
336	*/
337	public static Future<Object> execute(Executor executor, PrivilegedExceptionAction action) {
338	Callable<Object> task = new PrivilegedExceptionActionAdapter(action);
339	FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
340	executor.execute(future);
341	return future;
342	}
343
344	private static class PrivilegedActionAdapter implements Callable<Object> {
345	PrivilegedActionAdapter(PrivilegedAction action) {
346	this.action = action;
347	}
348	public Object call () {
349	return action.run();
350	}
351	private final PrivilegedAction action;
352	}
353
354	private static class PrivilegedExceptionActionAdapter implements Callable<Object> {
355	PrivilegedExceptionActionAdapter(PrivilegedExceptionAction action) {
356	this.action = action;
357	}
358	public Object call () throws Exception {
359	return action.run();
360	}
361	private final PrivilegedExceptionAction action;
362	}
363
364	/**
365	* Return a default thread factory used to create new threads.
366	* This factory creates all new threads used by an Executor in the
367	* same {@link ThreadGroup}. If there is a {@link
368	* java.lang.SecurityManager}, it uses the group of {@link
369	* System#getSecurityManager}, else the group of the thread
370	* invoking this <tt>defaultThreadFactory</tt> method. Each new
371	* thread is created as a non-daemon thread with priority
372	* <tt>Thread.NORM_PRIORITY</tt>. New threads have names
373	* accessible via {@link Thread#getName} of
374	* <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
375	* number of this factory, and <em>M</em> is the sequence number
376	* of the thread created by this factory.
377	* @return the thread factory
378	*/
379	public static ThreadFactory defaultThreadFactory() {
380	return new DefaultThreadFactory();
381	}
382
383	/**
384	* Return a thread factory used to create new threads that
385	* have the same permissions as the current thread.
386	* This factory creates threads with the same settings as {@link
387	* Executors#defaultThreadFactory}, additionally setting the
388	* AccessControlContext and contextClassLoader of new threads to
389	* be the same as the thread invoking this
390	* <tt>privilegedThreadFactory</tt> method. A new
391	* <tt>privilegedThreadFactory</tt> can be created within an
392	* {@link AccessController#doPrivileged} action setting the
393	* current thread's access control context to create threads with
394	* the selected permission settings holding within that action.
395	*
396	* <p> Note that while tasks running within such threads will have
397	* the same access control and class loader settings as the
398	* current thread, they need not have the same {@link
399	* java.lang.ThreadLocal} or {@link
400	* java.lang.InheritableThreadLocal} values. If necessary,
401	* particular values of thread locals can be set or reset before
402	* any task runs in {@link ThreadPoolExecutor} subclasses using
403	* {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
404	* necessary to initialize worker threads to have the same
405	* InheritableThreadLocal settings as some other designated
406	* thread, you can create a custom ThreadFactory in which that
407	* thread waits for and services requests to create others that
408	* will inherit its values.
409	*
410	* @return the thread factory
411	* @throws AccessControlException if the current access control
412	* context does not have permission to both get and set context
413	* class loader.
414	* @see PrivilegedFutureTask
415	*/
416	public static ThreadFactory privilegedThreadFactory() {
417	return new PrivilegedThreadFactory();
418	}
419
420	static class DefaultThreadFactory implements ThreadFactory {
421	static final AtomicInteger poolNumber = new AtomicInteger(1);
422	final ThreadGroup group;
423	final AtomicInteger threadNumber = new AtomicInteger(1);
424	final String namePrefix;
425
426	DefaultThreadFactory() {
427	SecurityManager s = System.getSecurityManager();
428	group = (s != null)? s.getThreadGroup() :
429	Thread.currentThread().getThreadGroup();
430	namePrefix = "pool-" +
431	poolNumber.getAndIncrement() +
432	"-thread-";
433	}
434
435	public Thread newThread(Runnable r) {
436	Thread t = new Thread(group, r,
437	namePrefix + threadNumber.getAndIncrement(),
438	0);
439	if (t.isDaemon())
440	t.setDaemon(false);
441	if (t.getPriority() != Thread.NORM_PRIORITY)
442	t.setPriority(Thread.NORM_PRIORITY);
443	return t;
444	}
445	}
446
447	static class PrivilegedThreadFactory extends DefaultThreadFactory {
448	private final ClassLoader ccl;
449	private final AccessControlContext acc;
450
451	PrivilegedThreadFactory() {
452	super();
453	this.ccl = Thread.currentThread().getContextClassLoader();
454	this.acc = AccessController.getContext();
455	acc.checkPermission(new RuntimePermission("setContextClassLoader"));
456	}
457
458	public Thread newThread(final Runnable r) {
459	return super.newThread(new Runnable() {
460	public void run() {
461	AccessController.doPrivileged(new PrivilegedAction() {
462	public Object run() {
463	Thread.currentThread().setContextClassLoader(ccl);
464	r.run();
465	return null;
466	}
467	}, acc);
468	}
469	});
470	}
471
472	}
473
474
475	/** Cannot instantiate. */
476	private Executors() {}
477	}