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 newly created scheduled thread pool with termination management
     */
    public static ScheduledExecutorService newScheduledThreadPool() {
        return newScheduledThreadPool(1);
    }
    
    /**
     * Creates a thread pool that can schedule commands to run after a 
     * given delay, or to execute periodically.
     * @param corePoolSize the number of threads to keep in the pool,
     * even if they are idle.
     * @return a newly created scheduled thread pool with termination management
     */
    public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
        return new 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 newly created scheduled thread pool with termination management
     */
    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:	1.29
Committed:	Sun Dec 7 15:00:46 2003 UTC (20 years, 6 months ago) by tim
Branch:	MAIN
Changes since 1.28:	+3 -6 lines
Log Message:	ScheduledExecutorService for Executors factory method return type
#	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	tim	1.26
43			/**
44			* A wrapper class that exposes only the ExecutorService and
45			* ScheduleExecutor methods of a ScheduledThreadPoolExecutor.
46			*/
47	tim	1.27	private static class DelegatedScheduledExecutorService
48	tim	1.28	extends DelegatedExecutorService
49			implements ScheduledExecutorService {
50	tim	1.26	private final ScheduledExecutor e;
51	tim	1.28	DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
52	tim	1.26	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	dl	1.2
69			/**
70	tim	1.1	* Creates a thread pool that reuses a fixed set of threads
71	dl	1.16	* 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	tim	1.1	*
76			* @param nThreads the number of threads in the pool
77			* @return the newly created thread pool
78			*/
79	dl	1.2	public static ExecutorService newFixedThreadPool(int nThreads) {
80			return new DelegatedExecutorService
81			(new ThreadPoolExecutor(nThreads, nThreads,
82			0L, TimeUnit.MILLISECONDS,
83	dl	1.3	new LinkedBlockingQueue<Runnable>()));
84	dl	1.2	}
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	dl	1.12	* @param threadFactory the factory to use when creating new threads
93	dl	1.2	* @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	dl	1.3	new LinkedBlockingQueue<Runnable>(),
100	dl	1.14	threadFactory));
101	dl	1.2	}
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	dl	1.16	* given time. This method is equivalent in effect to
111			*<tt>new FixedThreadPool(1)</tt>.
112	dl	1.2	*
113			* @return the newly-created single-threaded Executor
114			*/
115			public static ExecutorService newSingleThreadExecutor() {
116			return new DelegatedExecutorService
117	tim	1.6	(new ThreadPoolExecutor(1, 1,
118	dl	1.2	0L, TimeUnit.MILLISECONDS,
119	dl	1.3	new LinkedBlockingQueue<Runnable>()));
120	dl	1.2	}
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	dl	1.12	* @param threadFactory the factory to use when creating new
127	dl	1.2	* threads
128			*
129			* @return the newly-created single-threaded Executor
130			*/
131			public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
132			return new DelegatedExecutorService
133	tim	1.6	(new ThreadPoolExecutor(1, 1,
134	dl	1.2	0L, TimeUnit.MILLISECONDS,
135	dl	1.3	new LinkedBlockingQueue<Runnable>(),
136	dl	1.14	threadFactory));
137	tim	1.1	}
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	dl	1.16	* 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	tim	1.1	*
153			* @return the newly created thread pool
154			*/
155	dl	1.2	public static ExecutorService newCachedThreadPool() {
156			return new DelegatedExecutorService
157			(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
158			60, TimeUnit.SECONDS,
159	dl	1.3	new SynchronousQueue<Runnable>()));
160	tim	1.1	}
161
162			/**
163	dl	1.2	* Creates a thread pool that creates new threads as needed, but
164			* will reuse previously constructed threads when they are
165	tim	1.6	* available, and uses the provided
166	dl	1.2	* ThreadFactory to create new threads when needed.
167	dl	1.12	* @param threadFactory the factory to use when creating new threads
168	tim	1.1	* @return the newly created thread pool
169			*/
170	dl	1.2	public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
171			return new DelegatedExecutorService
172			(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
173			60, TimeUnit.SECONDS,
174	dl	1.3	new SynchronousQueue<Runnable>(),
175	dl	1.14	threadFactory));
176	tim	1.1	}
177	tim	1.27
178	tim	1.26	/**
179			* Creates a thread pool that can schedule commands to run after a
180			* given delay, or to execute periodically.
181	tim	1.29	* @return a newly created scheduled thread pool with termination management
182	tim	1.26	*/
183	tim	1.28	public static ScheduledExecutorService newScheduledThreadPool() {
184	tim	1.27	return newScheduledThreadPool(1);
185	tim	1.26	}
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	tim	1.29	* @return a newly created scheduled thread pool with termination management
193	tim	1.26	*/
194	tim	1.28	public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
195	tim	1.27	return new DelegatedScheduledExecutorService
196			(new ScheduledThreadPoolExecutor(corePoolSize));
197	tim	1.26	}
198
199			/**
200			* Creates a thread pool that can schedule commands to run after a
201			* given delay, or to execute periodically.
202			* @param corePoolSize the number of threads to keep in the pool,
203			* even if they are idle.
204			* @param threadFactory the factory to use when the executor
205			* creates a new thread.
206	tim	1.29	* @return a newly created scheduled thread pool with termination management
207	tim	1.26	*/
208	tim	1.28	public static ScheduledExecutorService newScheduledThreadPool(
209			int corePoolSize, ThreadFactory threadFactory) {
210	tim	1.27	return new DelegatedScheduledExecutorService
211			(new ScheduledThreadPoolExecutor(corePoolSize, threadFactory));
212	tim	1.26	}
213	tim	1.1
214			/**
215	dl	1.25	* Executes a Runnable task and returns a Future representing that
216	tim	1.15	* task.
217			*
218			* @param executor the Executor to which the task will be submitted
219			* @param task the task to submit
220	dl	1.25	* @return a Future representing pending completion of the task,
221			* and whose <tt>get()</tt> method will return <tt>Boolean.TRUE</tt>
222			* upon completion
223	tim	1.15	* @throws RejectedExecutionException if task cannot be scheduled
224			* for execution
225			*/
226	dl	1.25	public static Future<Boolean> execute(Executor executor, Runnable task) {
227	tim	1.15	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
228			executor.execute(ftask);
229			return ftask;
230			}
231
232			/**
233	tim	1.1	* Executes a Runnable task and returns a Future representing that
234			* task.
235			*
236			* @param executor the Executor to which the task will be submitted
237			* @param task the task to submit
238			* @param value the value which will become the return value of
239			* the task upon task completion
240	dl	1.5	* @return a Future representing pending completion of the task
241	jozart	1.9	* @throws RejectedExecutionException if task cannot be scheduled
242	tim	1.1	* for execution
243			*/
244	dl	1.5	public static <T> Future<T> execute(Executor executor, Runnable task, T value) {
245	dl	1.10	FutureTask<T> ftask = new FutureTask<T>(task, value);
246	tim	1.1	executor.execute(ftask);
247			return ftask;
248			}
249
250			/**
251			* Executes a value-returning task and returns a Future
252			* representing the pending results of the task.
253			*
254			* @param executor the Executor to which the task will be submitted
255			* @param task the task to submit
256			* @return a Future representing pending completion of the task
257	jozart	1.9	* @throws RejectedExecutionException if task cannot be scheduled
258			* for execution
259	tim	1.1	*/
260	tim	1.15	public static <T> Future<T> execute(Executor executor, Callable<T> task) {
261	dl	1.10	FutureTask<T> ftask = new FutureTask<T>(task);
262	tim	1.1	executor.execute(ftask);
263			return ftask;
264			}
265
266			/**
267			* Executes a Runnable task and blocks until it completes normally
268			* or throws an exception.
269			*
270			* @param executor the Executor to which the task will be submitted
271			* @param task the task to submit
272	jozart	1.9	* @throws RejectedExecutionException if task cannot be scheduled
273			* for execution
274	dl	1.19	* @throws ExecutionException if the task encountered an exception
275			* while executing
276	tim	1.1	*/
277			public static void invoke(Executor executor, Runnable task)
278			throws ExecutionException, InterruptedException {
279	tim	1.13	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
280	tim	1.1	executor.execute(ftask);
281			ftask.get();
282			}
283
284			/**
285			* Executes a value-returning task and blocks until it returns a
286			* value or throws an exception.
287			*
288			* @param executor the Executor to which the task will be submitted
289			* @param task the task to submit
290			* @return a Future representing pending completion of the task
291	jozart	1.9	* @throws RejectedExecutionException if task cannot be scheduled
292			* for execution
293	dl	1.12	* @throws InterruptedException if interrupted while waiting for
294			* completion
295	dl	1.19	* @throws ExecutionException if the task encountered an exception
296			* while executing
297	tim	1.1	*/
298			public static <T> T invoke(Executor executor, Callable<T> task)
299			throws ExecutionException, InterruptedException {
300			FutureTask<T> ftask = new FutureTask<T>(task);
301			executor.execute(ftask);
302			return ftask.get();
303	tim	1.6	}
304
305	tim	1.20
306			/**
307			* Executes a privileged action under the current access control
308			* context and returns a Future representing the pending result
309			* object of that action.
310			*
311			* @param executor the Executor to which the task will be submitted
312			* @param action the action to submit
313			* @return a Future representing pending completion of the action
314			* @throws RejectedExecutionException if action cannot be scheduled
315			* for execution
316			*/
317			public static Future<Object> execute(Executor executor, PrivilegedAction action) {
318			Callable<Object> task = new PrivilegedActionAdapter(action);
319	tim	1.21	FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
320	tim	1.20	executor.execute(future);
321			return future;
322			}
323
324			/**
325			* Executes a privileged exception action under the current access control
326			* context and returns a Future representing the pending result
327			* object of that action.
328			*
329			* @param executor the Executor to which the task will be submitted
330			* @param action the action to submit
331			* @return a Future representing pending completion of the action
332			* @throws RejectedExecutionException if action cannot be scheduled
333			* for execution
334			*/
335			public static Future<Object> execute(Executor executor, PrivilegedExceptionAction action) {
336			Callable<Object> task = new PrivilegedExceptionActionAdapter(action);
337	tim	1.21	FutureTask<Object> future = new PrivilegedFutureTask<Object>(task);
338	tim	1.20	executor.execute(future);
339			return future;
340			}
341
342			private static class PrivilegedActionAdapter implements Callable<Object> {
343			PrivilegedActionAdapter(PrivilegedAction action) {
344			this.action = action;
345			}
346			public Object call () {
347			return action.run();
348			}
349			private final PrivilegedAction action;
350			}
351
352			private static class PrivilegedExceptionActionAdapter implements Callable<Object> {
353			PrivilegedExceptionActionAdapter(PrivilegedExceptionAction action) {
354			this.action = action;
355			}
356			public Object call () throws Exception {
357			return action.run();
358			}
359			private final PrivilegedExceptionAction action;
360			}
361
362	dl	1.22	/**
363			* Return a default thread factory used to create new threads.
364			* This factory creates all new threads used by an Executor in the
365			* same {@link ThreadGroup}. If there is a {@link
366			* java.lang.SecurityManager}, it uses the group of {@link
367			* System#getSecurityManager}, else the group of the thread
368			* invoking this <tt>defaultThreadFactory</tt> method. Each new
369			* thread is created as a non-daemon thread with priority
370			* <tt>Thread.NORM_PRIORITY</tt>. New threads have names
371			* accessible via {@link Thread#getName} of
372			* <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
373			* number of this factory, and <em>M</em> is the sequence number
374			* of the thread created by this factory.
375			* @return the thread factory
376			*/
377			public static ThreadFactory defaultThreadFactory() {
378	tim	1.26	return new DefaultThreadFactory();
379	dl	1.22	}
380
381			/**
382	dl	1.24	* Return a thread factory used to create new threads that
383			* have the same permissions as the current thread.
384	dl	1.22	* This factory creates threads with the same settings as {@link
385			* Executors#defaultThreadFactory}, additionally setting the
386			* AccessControlContext and contextClassLoader of new threads to
387			* be the same as the thread invoking this
388			* <tt>privilegedThreadFactory</tt> method. A new
389			* <tt>privilegedThreadFactory</tt> can be created within an
390	dl	1.23	* {@link AccessController#doPrivileged} action setting the
391	dl	1.24	* current thread's access control context to create threads with
392	dl	1.23	* the selected permission settings holding within that action.
393	dl	1.22	*
394			* <p> Note that while tasks running within such threads will have
395			* the same access control and class loader settings as the
396			* current thread, they need not have the same {@link
397			* java.lang.ThreadLocal} or {@link
398			* java.lang.InheritableThreadLocal} values. If necessary,
399			* particular values of thread locals can be set or reset before
400			* any task runs in {@link ThreadPoolExecutor} subclasses using
401			* {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
402			* necessary to initialize worker threads to have the same
403			* InheritableThreadLocal settings as some other designated
404			* thread, you can create a custom ThreadFactory in which that
405			* thread waits for and services requests to create others that
406			* will inherit its values.
407			*
408			* @return the thread factory
409			* @throws AccessControlException if the current access control
410			* context does not have permission to both get and set context
411			* class loader.
412			* @see PrivilegedFutureTask
413			*/
414			public static ThreadFactory privilegedThreadFactory() {
415	tim	1.26	return new PrivilegedThreadFactory();
416	dl	1.22	}
417
418			static class DefaultThreadFactory implements ThreadFactory {
419	tim	1.26	static final AtomicInteger poolNumber = new AtomicInteger(1);
420			final ThreadGroup group;
421			final AtomicInteger threadNumber = new AtomicInteger(1);
422			final String namePrefix;
423	dl	1.22
424	tim	1.26	DefaultThreadFactory() {
425	dl	1.22	SecurityManager s = System.getSecurityManager();
426			group = (s != null)? s.getThreadGroup() :
427			Thread.currentThread().getThreadGroup();
428			namePrefix = "pool-" +
429			poolNumber.getAndIncrement() +
430			"-thread-";
431			}
432
433			public Thread newThread(Runnable r) {
434			Thread t = new Thread(group, r,
435			namePrefix + threadNumber.getAndIncrement(),
436			0);
437			if (t.isDaemon())
438			t.setDaemon(false);
439			if (t.getPriority() != Thread.NORM_PRIORITY)
440			t.setPriority(Thread.NORM_PRIORITY);
441			return t;
442			}
443			}
444
445			static class PrivilegedThreadFactory extends DefaultThreadFactory {
446			private final ClassLoader ccl;
447			private final AccessControlContext acc;
448
449			PrivilegedThreadFactory() {
450			super();
451			this.ccl = Thread.currentThread().getContextClassLoader();
452			this.acc = AccessController.getContext();
453			acc.checkPermission(new RuntimePermission("setContextClassLoader"));
454			}
455
456			public Thread newThread(final Runnable r) {
457			return super.newThread(new Runnable() {
458			public void run() {
459			AccessController.doPrivileged(new PrivilegedAction() {
460			public Object run() {
461			Thread.currentThread().setContextClassLoader(ccl);
462			r.run();
463			return null;
464			}
465			}, acc);
466			}
467			});
468			}
469
470			}
471
472	tim	1.20
473	tim	1.15	/** Cannot instantiate. */
474			private Executors() {}
475	tim	1.1	}