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);
        }
    }

    /**
     * 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));
    }

    /**
     * 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:	1.25
Committed:	Thu Dec 4 20:54:29 2003 UTC (20 years, 6 months ago) by dl
Branch:	MAIN
Changes since 1.24:	+7 -5 lines
Log Message:	Revised tests for revised Future classes
#	User	Rev	Content
1	tim	1.1	/*
2	dl	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	tim	1.1	*/
6
7			package java.util.concurrent;
8	dl	1.2	import java.util.*;
9	dl	1.22	import java.util.concurrent.atomic.AtomicInteger;
10	tim	1.20	import java.security.AccessControlContext;
11			import java.security.AccessController;
12			import java.security.PrivilegedAction;
13			import java.security.PrivilegedExceptionAction;
14	tim	1.1
15			/**
16	dl	1.18	* Factory and utility methods for {@link Executor}, {@link
17	dl	1.25	* ExecutorService}, {@link ThreadFactory}, and {@link Future}
18			* classes defined in this package.
19	tim	1.1	*
20			* @since 1.5
21	dl	1.12	* @author Doug Lea
22	tim	1.1	*/
23			public class Executors {
24
25			/**
26	dl	1.2	* A wrapper class that exposes only the ExecutorService methods
27			* of an implementation.
28	tim	1.6	*/
29	jozart	1.11	private static class DelegatedExecutorService implements ExecutorService {
30	dl	1.2	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	tim	1.1	* Creates a thread pool that reuses a fixed set of threads
45	dl	1.16	* operating off a shared unbounded queue. If any thread
46			* terminates due to a failure during execution prior to shutdown,
47			* a new one will take its place if needed to execute subsequent
48			* tasks.
49	tim	1.1	*
50			* @param nThreads the number of threads in the pool
51			* @return the newly created thread pool
52			*/
53	dl	1.2	public static ExecutorService newFixedThreadPool(int nThreads) {
54			return new DelegatedExecutorService
55			(new ThreadPoolExecutor(nThreads, nThreads,
56			0L, TimeUnit.MILLISECONDS,
57	dl	1.3	new LinkedBlockingQueue<Runnable>()));
58	dl	1.2	}
59
60			/**
61			* Creates a thread pool that reuses a fixed set of threads
62			* operating off a shared unbounded queue, using the provided
63			* ThreadFactory to create new threads when needed.
64			*
65			* @param nThreads the number of threads in the pool
66	dl	1.12	* @param threadFactory the factory to use when creating new threads
67	dl	1.2	* @return the newly created thread pool
68			*/
69			public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
70			return new DelegatedExecutorService
71			(new ThreadPoolExecutor(nThreads, nThreads,
72			0L, TimeUnit.MILLISECONDS,
73	dl	1.3	new LinkedBlockingQueue<Runnable>(),
74	dl	1.14	threadFactory));
75	dl	1.2	}
76
77			/**
78			* Creates an Executor that uses a single worker thread operating
79			* off an unbounded queue. (Note however that if this single
80			* thread terminates due to a failure during execution prior to
81			* shutdown, a new one will take its place if needed to execute
82			* subsequent tasks.) Tasks are guaranteed to execute
83			* sequentially, and no more than one task will be active at any
84	dl	1.16	* given time. This method is equivalent in effect to
85			*<tt>new FixedThreadPool(1)</tt>.
86	dl	1.2	*
87			* @return the newly-created single-threaded Executor
88			*/
89			public static ExecutorService newSingleThreadExecutor() {
90			return new DelegatedExecutorService
91	tim	1.6	(new ThreadPoolExecutor(1, 1,
92	dl	1.2	0L, TimeUnit.MILLISECONDS,
93	dl	1.3	new LinkedBlockingQueue<Runnable>()));
94	dl	1.2	}
95
96			/**
97			* Creates an Executor that uses a single worker thread operating
98			* off an unbounded queue, and uses the provided ThreadFactory to
99			* create new threads when needed.
100	dl	1.12	* @param threadFactory the factory to use when creating new
101	dl	1.2	* threads
102			*
103			* @return the newly-created single-threaded Executor
104			*/
105			public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
106			return new DelegatedExecutorService
107	tim	1.6	(new ThreadPoolExecutor(1, 1,
108	dl	1.2	0L, TimeUnit.MILLISECONDS,
109	dl	1.3	new LinkedBlockingQueue<Runnable>(),
110	dl	1.14	threadFactory));
111	tim	1.1	}
112
113			/**
114			* Creates a thread pool that creates new threads as needed, but
115			* will reuse previously constructed threads when they are
116			* available. These pools will typically improve the performance
117			* of programs that execute many short-lived asynchronous tasks.
118			* Calls to <tt>execute</tt> will reuse previously constructed
119			* threads if available. If no existing thread is available, a new
120			* thread will be created and added to the pool. Threads that have
121			* not been used for sixty seconds are terminated and removed from
122			* the cache. Thus, a pool that remains idle for long enough will
123	dl	1.16	* not consume any resources. Note that pools with similar
124			* properties but different details (for example, timeout parameters)
125			* may be created using {@link ThreadPoolExecutor} constructors.
126	tim	1.1	*
127			* @return the newly created thread pool
128			*/
129	dl	1.2	public static ExecutorService newCachedThreadPool() {
130			return new DelegatedExecutorService
131			(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
132			60, TimeUnit.SECONDS,
133	dl	1.3	new SynchronousQueue<Runnable>()));
134	tim	1.1	}
135
136			/**
137	dl	1.2	* Creates a thread pool that creates new threads as needed, but
138			* will reuse previously constructed threads when they are
139	tim	1.6	* available, and uses the provided
140	dl	1.2	* ThreadFactory to create new threads when needed.
141	dl	1.12	* @param threadFactory the factory to use when creating new threads
142	tim	1.1	* @return the newly created thread pool
143			*/
144	dl	1.2	public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
145			return new DelegatedExecutorService
146			(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
147			60, TimeUnit.SECONDS,
148	dl	1.3	new SynchronousQueue<Runnable>(),
149	dl	1.14	threadFactory));
150	tim	1.1	}
151
152			/**
153	dl	1.25	* Executes a Runnable task and returns a Future representing that
154	tim	1.15	* task.
155			*
156			* @param executor the Executor to which the task will be submitted
157			* @param task the task to submit
158	dl	1.25	* @return a Future representing pending completion of the task,
159			* and whose <tt>get()</tt> method will return <tt>Boolean.TRUE</tt>
160			* upon completion
161	tim	1.15	* @throws RejectedExecutionException if task cannot be scheduled
162			* for execution
163			*/
164	dl	1.25	public static Future<Boolean> execute(Executor executor, Runnable task) {
165	tim	1.15	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
166			executor.execute(ftask);
167			return ftask;
168			}
169
170			/**
171	tim	1.1	* Executes a Runnable task and returns a Future representing that
172			* task.
173			*
174			* @param executor the Executor to which the task will be submitted
175			* @param task the task to submit
176			* @param value the value which will become the return value of
177			* the task upon task completion
178	dl	1.5	* @return a Future representing pending completion of the task
179	jozart	1.9	* @throws RejectedExecutionException if task cannot be scheduled
180	tim	1.1	* for execution
181			*/
182	dl	1.5	public static <T> Future<T> execute(Executor executor, Runnable task, T value) {
183	dl	1.10	FutureTask<T> ftask = new FutureTask<T>(task, value);
184	tim	1.1	executor.execute(ftask);
185			return ftask;
186			}
187
188			/**
189			* Executes a value-returning task and returns a Future
190			* representing the pending results of the task.
191			*
192			* @param executor the Executor to which the task will be submitted
193			* @param task the task to submit
194			* @return a Future representing pending completion of the task
195	jozart	1.9	* @throws RejectedExecutionException if task cannot be scheduled
196			* for execution
197	tim	1.1	*/
198	tim	1.15	public static <T> Future<T> execute(Executor executor, Callable<T> task) {
199	dl	1.10	FutureTask<T> ftask = new FutureTask<T>(task);
200	tim	1.1	executor.execute(ftask);
201			return ftask;
202			}
203
204			/**
205			* Executes a Runnable task and blocks until it completes normally
206			* or throws an exception.
207			*
208			* @param executor the Executor to which the task will be submitted
209			* @param task the task to submit
210	jozart	1.9	* @throws RejectedExecutionException if task cannot be scheduled
211			* for execution
212	dl	1.19	* @throws ExecutionException if the task encountered an exception
213			* while executing
214	tim	1.1	*/
215			public static void invoke(Executor executor, Runnable task)
216			throws ExecutionException, InterruptedException {
217	tim	1.13	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
218	tim	1.1	executor.execute(ftask);
219			ftask.get();
220			}
221
222			/**
223			* Executes a value-returning task and blocks until it returns a
224			* value or throws an exception.
225			*
226			* @param executor the Executor to which the task will be submitted
227			* @param task the task to submit
228			* @return a Future representing pending completion of the task
229	jozart	1.9	* @throws RejectedExecutionException if task cannot be scheduled
230			* for execution
231	dl	1.12	* @throws InterruptedException if interrupted while waiting for
232			* completion
233	dl	1.19	* @throws ExecutionException if the task encountered an exception
234			* while executing
235	tim	1.1	*/
236			public static <T> T invoke(Executor executor, Callable<T> task)
237			throws ExecutionException, InterruptedException {
238			FutureTask<T> ftask = new FutureTask<T>(task);
239			executor.execute(ftask);
240			return ftask.get();
241	tim	1.6	}
242
243	tim	1.20
244			/**
245			* Executes a privileged action under the current access control
246			* context and returns a Future representing the pending result
247			* object of that action.
248			*
249			* @param executor the Executor to which the task will be submitted
250			* @param action the action to submit
251			* @return a Future representing pending completion of the action
252			* @throws RejectedExecutionException if action cannot be scheduled
253			* for execution
254			*/
255			public static Future<Object> execute(Executor executor, PrivilegedAction action) {
256			Callable<Object> task = new PrivilegedActionAdapter(action);
257	tim	1.21	FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
258	tim	1.20	executor.execute(future);
259			return future;
260			}
261
262			/**
263			* Executes a privileged exception action under the current access control
264			* context and returns a Future representing the pending result
265			* object of that action.
266			*
267			* @param executor the Executor to which the task will be submitted
268			* @param action the action to submit
269			* @return a Future representing pending completion of the action
270			* @throws RejectedExecutionException if action cannot be scheduled
271			* for execution
272			*/
273			public static Future<Object> execute(Executor executor, PrivilegedExceptionAction action) {
274			Callable<Object> task = new PrivilegedExceptionActionAdapter(action);
275	tim	1.21	FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
276	tim	1.20	executor.execute(future);
277			return future;
278			}
279
280			private static class PrivilegedActionAdapter implements Callable<Object> {
281			PrivilegedActionAdapter(PrivilegedAction action) {
282			this.action = action;
283			}
284			public Object call () {
285			return action.run();
286			}
287			private final PrivilegedAction action;
288			}
289
290			private static class PrivilegedExceptionActionAdapter implements Callable<Object> {
291			PrivilegedExceptionActionAdapter(PrivilegedExceptionAction action) {
292			this.action = action;
293			}
294			public Object call () throws Exception {
295			return action.run();
296			}
297			private final PrivilegedExceptionAction action;
298			}
299
300	dl	1.22	/**
301			* Return a default thread factory used to create new threads.
302			* This factory creates all new threads used by an Executor in the
303			* same {@link ThreadGroup}. If there is a {@link
304			* java.lang.SecurityManager}, it uses the group of {@link
305			* System#getSecurityManager}, else the group of the thread
306			* invoking this <tt>defaultThreadFactory</tt> method. Each new
307			* thread is created as a non-daemon thread with priority
308			* <tt>Thread.NORM_PRIORITY</tt>. New threads have names
309			* accessible via {@link Thread#getName} of
310			* <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
311			* number of this factory, and <em>M</em> is the sequence number
312			* of the thread created by this factory.
313			* @return the thread factory
314			*/
315			public static ThreadFactory defaultThreadFactory() {
316			return new DefaultThreadFactory();
317			}
318
319			/**
320	dl	1.24	* Return a thread factory used to create new threads that
321			* have the same permissions as the current thread.
322	dl	1.22	* This factory creates threads with the same settings as {@link
323			* Executors#defaultThreadFactory}, additionally setting the
324			* AccessControlContext and contextClassLoader of new threads to
325			* be the same as the thread invoking this
326			* <tt>privilegedThreadFactory</tt> method. A new
327			* <tt>privilegedThreadFactory</tt> can be created within an
328	dl	1.23	* {@link AccessController#doPrivileged} action setting the
329	dl	1.24	* current thread's access control context to create threads with
330	dl	1.23	* the selected permission settings holding within that action.
331	dl	1.22	*
332			* <p> Note that while tasks running within such threads will have
333			* the same access control and class loader settings as the
334			* current thread, they need not have the same {@link
335			* java.lang.ThreadLocal} or {@link
336			* java.lang.InheritableThreadLocal} values. If necessary,
337			* particular values of thread locals can be set or reset before
338			* any task runs in {@link ThreadPoolExecutor} subclasses using
339			* {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
340			* necessary to initialize worker threads to have the same
341			* InheritableThreadLocal settings as some other designated
342			* thread, you can create a custom ThreadFactory in which that
343			* thread waits for and services requests to create others that
344			* will inherit its values.
345			*
346			* @return the thread factory
347			* @throws AccessControlException if the current access control
348			* context does not have permission to both get and set context
349			* class loader.
350			* @see PrivilegedFutureTask
351			*/
352			public static ThreadFactory privilegedThreadFactory() {
353			return new PrivilegedThreadFactory();
354			}
355
356			static class DefaultThreadFactory implements ThreadFactory {
357			static final AtomicInteger poolNumber = new AtomicInteger(1);
358			final ThreadGroup group;
359			final AtomicInteger threadNumber = new AtomicInteger(1);
360			final String namePrefix;
361
362			DefaultThreadFactory() {
363			SecurityManager s = System.getSecurityManager();
364			group = (s != null)? s.getThreadGroup() :
365			Thread.currentThread().getThreadGroup();
366			namePrefix = "pool-" +
367			poolNumber.getAndIncrement() +
368			"-thread-";
369			}
370
371			public Thread newThread(Runnable r) {
372			Thread t = new Thread(group, r,
373			namePrefix + threadNumber.getAndIncrement(),
374			0);
375			if (t.isDaemon())
376			t.setDaemon(false);
377			if (t.getPriority() != Thread.NORM_PRIORITY)
378			t.setPriority(Thread.NORM_PRIORITY);
379			return t;
380			}
381			}
382
383			static class PrivilegedThreadFactory extends DefaultThreadFactory {
384			private final ClassLoader ccl;
385			private final AccessControlContext acc;
386
387			PrivilegedThreadFactory() {
388			super();
389			this.ccl = Thread.currentThread().getContextClassLoader();
390			this.acc = AccessController.getContext();
391			acc.checkPermission(new RuntimePermission("setContextClassLoader"));
392			}
393
394			public Thread newThread(final Runnable r) {
395			return super.newThread(new Runnable() {
396			public void run() {
397			AccessController.doPrivileged(new PrivilegedAction() {
398			public Object run() {
399			Thread.currentThread().setContextClassLoader(ccl);
400			r.run();
401			return null;
402			}
403			}, acc);
404			}
405			});
406			}
407
408			}
409
410	tim	1.20
411	tim	1.15	/** Cannot instantiate. */
412			private Executors() {}
413	tim	1.1	}