util/concurrent/Executors.java

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

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

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

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

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

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

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

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

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

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


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

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

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


    /**
     * Creates and returns a {@link Callable} object that, when
     * called, runs the given task and returns the given result.  This
     * can be useful when applying methods requiring a
     * <tt>Callable</tt> to an otherwise resultless action.
     * @param task the task to run
     * @param result the result to return
     */
    public static <T> Callable<T> callable(Runnable task, T result) {
        return new RunnableAdapter<T>(task, result);
    }

    /**
     * Creates and returns a {@link Callable} object that, when
     * called, runs the given task and returns <tt>null</tt>
     * @param task the task to run
     */
    public static Callable<Object> callable(Runnable task) {
        return new RunnableAdapter<Object>(task, null);
    }

    /**
     * Creates and returns a {@link Callable} object that, when
     * called, runs the given privileged action and returns its result
     * @param action the privileged action to run
     */
    public static Callable<Object> callable(PrivilegedAction action) {
        return new PrivilegedActionAdapter(action);
    }

    /**
     * Creates and returns a {@link Callable} object that, when
     * called, runs the given privileged exception action and returns its result
     * @param action the privileged exception action to run
     */
    public static Callable<Object> callable(PrivilegedExceptionAction action) {
        return new PrivilegedExceptionActionAdapter(action);
    }

    /**
     * A callable that runs given task and returns given result
     */
    static class RunnableAdapter<T> implements Callable<T> {
        private final Runnable task;
        private final T result;
        RunnableAdapter(Runnable  task, T result) {
            this.task = task; 
            this.result = result;
        }
        public T call() { 
            task.run(); 
            return result; 
        }
    }

    /**
     * A callable that runs given privileged action and returns its result
     */
    static class PrivilegedActionAdapter implements Callable<Object> {
        PrivilegedActionAdapter(PrivilegedAction action) {
            this.action = action;
        }
        public Object call () {
            return action.run();
        }
        private final PrivilegedAction action;
    }

    /**
     * A callable that runs given privileged exception action and returns its result
     */
    static class PrivilegedExceptionActionAdapter implements Callable<Object> {
        PrivilegedExceptionActionAdapter(PrivilegedExceptionAction action) {
            this.action = action;
        }
        public Object call () throws Exception {
            return action.run();
        }
        private final PrivilegedExceptionAction action;
    }

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

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

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

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

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

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

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

        
    /** Cannot instantiate. */
    private Executors() {}
}
Revision:	1.38
Committed:	Fri Dec 19 20:38:31 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.37:	+84 -30 lines
Log Message:	Define and use Executors.callable instead of submit/invoke variants
#	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	1.34	* ExecutorService}, and {@link ThreadFactory} classes defined in this
18			* 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			* Creates a thread pool that reuses a fixed set of threads
27	dl	1.16	* operating off a shared unbounded queue. If any thread
28			* terminates due to a failure during execution prior to shutdown,
29			* a new one will take its place if needed to execute subsequent
30			* tasks.
31	tim	1.1	*
32			* @param nThreads the number of threads in the pool
33			* @return the newly created thread pool
34			*/
35	dl	1.2	public static ExecutorService newFixedThreadPool(int nThreads) {
36	dl	1.35	return new ThreadPoolExecutor(nThreads, nThreads,
37			0L, TimeUnit.MILLISECONDS,
38			new LinkedBlockingQueue<Runnable>());
39	dl	1.2	}
40
41			/**
42			* Creates a thread pool that reuses a fixed set of threads
43			* operating off a shared unbounded queue, using the provided
44			* ThreadFactory to create new threads when needed.
45			*
46			* @param nThreads the number of threads in the pool
47	dl	1.12	* @param threadFactory the factory to use when creating new threads
48	dl	1.2	* @return the newly created thread pool
49			*/
50			public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
51	dl	1.35	return new ThreadPoolExecutor(nThreads, nThreads,
52			0L, TimeUnit.MILLISECONDS,
53			new LinkedBlockingQueue<Runnable>(),
54			threadFactory);
55	dl	1.2	}
56
57			/**
58			* Creates an Executor that uses a single worker thread operating
59			* off an unbounded queue. (Note however that if this single
60			* thread terminates due to a failure during execution prior to
61			* shutdown, a new one will take its place if needed to execute
62			* subsequent tasks.) Tasks are guaranteed to execute
63			* sequentially, and no more than one task will be active at any
64	dl	1.36	* given time. The returned executor cannot be reconfigured
65			* to use additional threads.
66	dl	1.2	*
67			* @return the newly-created single-threaded Executor
68			*/
69			public static ExecutorService newSingleThreadExecutor() {
70	dl	1.36	return unconfigurableExecutorService
71			(new ThreadPoolExecutor(1, 1,
72			0L, TimeUnit.MILLISECONDS,
73			new LinkedBlockingQueue<Runnable>()));
74	dl	1.2	}
75
76			/**
77			* Creates an Executor that uses a single worker thread operating
78			* off an unbounded queue, and uses the provided ThreadFactory to
79	dl	1.37	* create a new thread when needed. Unlike the otherwise
80			* equivalent <tt>newFixedThreadPool(1)</tt> the returned executor
81			* is guaranteed not to be reconfigurable to use additional
82			* threads.
83			*
84	dl	1.12	* @param threadFactory the factory to use when creating new
85	dl	1.2	* threads
86			*
87			* @return the newly-created single-threaded Executor
88			*/
89			public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
90	dl	1.36	return unconfigurableExecutorService
91			(new ThreadPoolExecutor(1, 1,
92			0L, TimeUnit.MILLISECONDS,
93			new LinkedBlockingQueue<Runnable>(),
94			threadFactory));
95	tim	1.1	}
96
97			/**
98			* Creates a thread pool that creates new threads as needed, but
99			* will reuse previously constructed threads when they are
100			* available. These pools will typically improve the performance
101			* of programs that execute many short-lived asynchronous tasks.
102			* Calls to <tt>execute</tt> will reuse previously constructed
103			* threads if available. If no existing thread is available, a new
104			* thread will be created and added to the pool. Threads that have
105			* not been used for sixty seconds are terminated and removed from
106			* the cache. Thus, a pool that remains idle for long enough will
107	dl	1.16	* not consume any resources. Note that pools with similar
108			* properties but different details (for example, timeout parameters)
109			* may be created using {@link ThreadPoolExecutor} constructors.
110	tim	1.1	*
111			* @return the newly created thread pool
112			*/
113	dl	1.2	public static ExecutorService newCachedThreadPool() {
114	dl	1.35	return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
115			60, TimeUnit.SECONDS,
116			new SynchronousQueue<Runnable>());
117	tim	1.1	}
118
119			/**
120	dl	1.2	* Creates a thread pool that creates new threads as needed, but
121			* will reuse previously constructed threads when they are
122	tim	1.6	* available, and uses the provided
123	dl	1.2	* ThreadFactory to create new threads when needed.
124	dl	1.12	* @param threadFactory the factory to use when creating new threads
125	tim	1.1	* @return the newly created thread pool
126			*/
127	dl	1.2	public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
128	dl	1.35	return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
129			60, TimeUnit.SECONDS,
130			new SynchronousQueue<Runnable>(),
131			threadFactory);
132	tim	1.1	}
133	tim	1.27
134	tim	1.26	/**
135			* Creates a thread pool that can schedule commands to run after a
136			* given delay, or to execute periodically.
137	tim	1.29	* @return a newly created scheduled thread pool with termination management
138	tim	1.26	*/
139	tim	1.28	public static ScheduledExecutorService newScheduledThreadPool() {
140	tim	1.27	return newScheduledThreadPool(1);
141	tim	1.26	}
142
143			/**
144			* Creates a thread pool that can schedule commands to run after a
145			* given delay, or to execute periodically.
146			* @param corePoolSize the number of threads to keep in the pool,
147			* even if they are idle.
148	tim	1.29	* @return a newly created scheduled thread pool with termination management
149	tim	1.26	*/
150	tim	1.28	public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
151	dl	1.35	return new ScheduledThreadPoolExecutor(corePoolSize);
152			}
153	tim	1.26
154			/**
155			* Creates a thread pool that can schedule commands to run after a
156			* given delay, or to execute periodically.
157			* @param corePoolSize the number of threads to keep in the pool,
158			* even if they are idle.
159			* @param threadFactory the factory to use when the executor
160			* creates a new thread.
161	tim	1.29	* @return a newly created scheduled thread pool with termination management
162	tim	1.26	*/
163	tim	1.28	public static ScheduledExecutorService newScheduledThreadPool(
164			int corePoolSize, ThreadFactory threadFactory) {
165	dl	1.35	return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
166	tim	1.20	}
167	dl	1.36
168
169			/**
170			* Creates and returns an object that delegates all defined {@link
171			* ExecutorService} methods to the given executor, but not any
172			* other methods that might otherwise be accessible using
173			* casts. This provides a way to safely "freeze" configuration and
174			* disallow tuning of a given concrete implementation.
175			* @param executor the underlying implementation
176			* @return an <tt>ExecutorService</tt> instance
177			* @throws NullPointerException if executor null
178			*/
179			public static ExecutorService unconfigurableExecutorService(ExecutorService executor) {
180			if (executor == null)
181			throw new NullPointerException();
182			return new DelegatedExecutorService(executor);
183			}
184
185			/**
186			* Creates and returns an object that delegates all defined {@link
187			* ScheduledExecutorService} methods to the given executor, but
188			* not any other methods that might otherwise be accessible using
189			* casts. This provides a way to safely "freeze" configuration and
190			* disallow tuning of a given concrete implementation.
191			* @param executor the underlying implementation
192			* @return a <tt>ScheduledExecutorService</tt> instance
193			* @throws NullPointerException if executor null
194			*/
195			public static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor) {
196			if (executor == null)
197			throw new NullPointerException();
198			return new DelegatedScheduledExecutorService(executor);
199			}
200	tim	1.20
201	dl	1.22	/**
202			* Return a default thread factory used to create new threads.
203			* This factory creates all new threads used by an Executor in the
204			* same {@link ThreadGroup}. If there is a {@link
205			* java.lang.SecurityManager}, it uses the group of {@link
206			* System#getSecurityManager}, else the group of the thread
207			* invoking this <tt>defaultThreadFactory</tt> method. Each new
208			* thread is created as a non-daemon thread with priority
209			* <tt>Thread.NORM_PRIORITY</tt>. New threads have names
210			* accessible via {@link Thread#getName} of
211			* <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
212			* number of this factory, and <em>M</em> is the sequence number
213			* of the thread created by this factory.
214			* @return the thread factory
215			*/
216			public static ThreadFactory defaultThreadFactory() {
217	tim	1.26	return new DefaultThreadFactory();
218	dl	1.22	}
219
220			/**
221	dl	1.24	* Return a thread factory used to create new threads that
222			* have the same permissions as the current thread.
223	dl	1.22	* This factory creates threads with the same settings as {@link
224			* Executors#defaultThreadFactory}, additionally setting the
225			* AccessControlContext and contextClassLoader of new threads to
226			* be the same as the thread invoking this
227			* <tt>privilegedThreadFactory</tt> method. A new
228			* <tt>privilegedThreadFactory</tt> can be created within an
229	dl	1.23	* {@link AccessController#doPrivileged} action setting the
230	dl	1.24	* current thread's access control context to create threads with
231	dl	1.23	* the selected permission settings holding within that action.
232	dl	1.22	*
233			* <p> Note that while tasks running within such threads will have
234			* the same access control and class loader settings as the
235			* current thread, they need not have the same {@link
236			* java.lang.ThreadLocal} or {@link
237			* java.lang.InheritableThreadLocal} values. If necessary,
238			* particular values of thread locals can be set or reset before
239			* any task runs in {@link ThreadPoolExecutor} subclasses using
240			* {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
241			* necessary to initialize worker threads to have the same
242			* InheritableThreadLocal settings as some other designated
243			* thread, you can create a custom ThreadFactory in which that
244			* thread waits for and services requests to create others that
245			* will inherit its values.
246			*
247			* @return the thread factory
248			* @throws AccessControlException if the current access control
249			* context does not have permission to both get and set context
250			* class loader.
251			* @see PrivilegedFutureTask
252			*/
253			public static ThreadFactory privilegedThreadFactory() {
254	tim	1.26	return new PrivilegedThreadFactory();
255	dl	1.22	}
256
257	dl	1.38
258			/**
259			* Creates and returns a {@link Callable} object that, when
260			* called, runs the given task and returns the given result. This
261			* can be useful when applying methods requiring a
262			* <tt>Callable</tt> to an otherwise resultless action.
263			* @param task the task to run
264			* @param result the result to return
265			*/
266			public static <T> Callable<T> callable(Runnable task, T result) {
267			return new RunnableAdapter<T>(task, result);
268			}
269
270			/**
271			* Creates and returns a {@link Callable} object that, when
272			* called, runs the given task and returns <tt>null</tt>
273			* @param task the task to run
274			*/
275			public static Callable<Object> callable(Runnable task) {
276			return new RunnableAdapter<Object>(task, null);
277			}
278
279			/**
280			* Creates and returns a {@link Callable} object that, when
281			* called, runs the given privileged action and returns its result
282			* @param action the privileged action to run
283			*/
284			public static Callable<Object> callable(PrivilegedAction action) {
285			return new PrivilegedActionAdapter(action);
286			}
287
288			/**
289			* Creates and returns a {@link Callable} object that, when
290			* called, runs the given privileged exception action and returns its result
291			* @param action the privileged exception action to run
292			*/
293			public static Callable<Object> callable(PrivilegedExceptionAction action) {
294			return new PrivilegedExceptionActionAdapter(action);
295			}
296
297			/**
298			* A callable that runs given task and returns given result
299			*/
300			static class RunnableAdapter<T> implements Callable<T> {
301			private final Runnable task;
302			private final T result;
303			RunnableAdapter(Runnable task, T result) {
304			this.task = task;
305			this.result = result;
306			}
307			public T call() {
308			task.run();
309			return result;
310			}
311			}
312
313			/**
314			* A callable that runs given privileged action and returns its result
315			*/
316			static class PrivilegedActionAdapter implements Callable<Object> {
317			PrivilegedActionAdapter(PrivilegedAction action) {
318			this.action = action;
319			}
320			public Object call () {
321			return action.run();
322			}
323			private final PrivilegedAction action;
324			}
325
326			/**
327			* A callable that runs given privileged exception action and returns its result
328			*/
329			static class PrivilegedExceptionActionAdapter implements Callable<Object> {
330			PrivilegedExceptionActionAdapter(PrivilegedExceptionAction action) {
331			this.action = action;
332			}
333			public Object call () throws Exception {
334			return action.run();
335			}
336			private final PrivilegedExceptionAction action;
337			}
338
339	dl	1.22	static class DefaultThreadFactory implements ThreadFactory {
340	tim	1.26	static final AtomicInteger poolNumber = new AtomicInteger(1);
341			final ThreadGroup group;
342			final AtomicInteger threadNumber = new AtomicInteger(1);
343			final String namePrefix;
344	dl	1.22
345	tim	1.26	DefaultThreadFactory() {
346	dl	1.22	SecurityManager s = System.getSecurityManager();
347			group = (s != null)? s.getThreadGroup() :
348			Thread.currentThread().getThreadGroup();
349			namePrefix = "pool-" +
350			poolNumber.getAndIncrement() +
351			"-thread-";
352			}
353
354			public Thread newThread(Runnable r) {
355			Thread t = new Thread(group, r,
356			namePrefix + threadNumber.getAndIncrement(),
357			0);
358			if (t.isDaemon())
359			t.setDaemon(false);
360			if (t.getPriority() != Thread.NORM_PRIORITY)
361			t.setPriority(Thread.NORM_PRIORITY);
362			return t;
363			}
364			}
365
366			static class PrivilegedThreadFactory extends DefaultThreadFactory {
367			private final ClassLoader ccl;
368			private final AccessControlContext acc;
369
370			PrivilegedThreadFactory() {
371			super();
372			this.ccl = Thread.currentThread().getContextClassLoader();
373			this.acc = AccessController.getContext();
374			acc.checkPermission(new RuntimePermission("setContextClassLoader"));
375			}
376
377			public Thread newThread(final Runnable r) {
378			return super.newThread(new Runnable() {
379			public void run() {
380			AccessController.doPrivileged(new PrivilegedAction() {
381			public Object run() {
382			Thread.currentThread().setContextClassLoader(ccl);
383			r.run();
384			return null;
385			}
386			}, acc);
387			}
388			});
389			}
390
391	dl	1.36	}
392
393			/**
394			* A wrapper class that exposes only the ExecutorService methods
395			* of an implementation.
396			*/
397	dl	1.37	static class DelegatedExecutorService extends AbstractExecutorService {
398	dl	1.36	private final ExecutorService e;
399			DelegatedExecutorService(ExecutorService executor) { e = executor; }
400			public void execute(Runnable command) { e.execute(command); }
401			public void shutdown() { e.shutdown(); }
402			public List<Runnable> shutdownNow() { return e.shutdownNow(); }
403			public boolean isShutdown() { return e.isShutdown(); }
404			public boolean isTerminated() { return e.isTerminated(); }
405			public boolean awaitTermination(long timeout, TimeUnit unit)
406			throws InterruptedException {
407			return e.awaitTermination(timeout, unit);
408			}
409	dl	1.38	public Future<?> submit(Runnable task) {
410			return e.submit(task);
411	dl	1.36	}
412			public <T> Future<T> submit(Callable<T> task) {
413			return e.submit(task);
414			}
415
416			public <T> T invoke(Callable<T> task) throws ExecutionException, InterruptedException {
417			return e.invoke(task);
418			}
419			public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
420			throws InterruptedException {
421			return e.invokeAll(tasks);
422			}
423			public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks,
424			long timeout, TimeUnit unit)
425			throws InterruptedException {
426			return e.invokeAll(tasks, timeout, unit);
427			}
428			public <T> T invokeAny(Collection<Callable<T>> tasks)
429			throws InterruptedException, ExecutionException {
430			return e.invokeAny(tasks);
431			}
432			public <T> T invokeAny(Collection<Callable<T>> tasks,
433			long timeout, TimeUnit unit)
434			throws InterruptedException, ExecutionException, TimeoutException {
435			return e.invokeAny(tasks, timeout, unit);
436			}
437			}
438
439			/**
440			* A wrapper class that exposes only the ExecutorService and
441			* ScheduleExecutor methods of a ScheduledThreadPoolExecutor.
442			*/
443	dl	1.37	static class DelegatedScheduledExecutorService
444	dl	1.36	extends DelegatedExecutorService
445			implements ScheduledExecutorService {
446			private final ScheduledExecutorService e;
447			DelegatedScheduledExecutorService(ScheduledExecutorService executor) {
448			super(executor);
449			e = executor;
450			}
451			public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
452			return e.schedule(command, delay, unit);
453			}
454			public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
455			return e.schedule(callable, delay, unit);
456			}
457			public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
458			return e.scheduleAtFixedRate(command, initialDelay, period, unit);
459			}
460			public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
461			return e.scheduleWithFixedDelay(command, initialDelay, delay, unit);
462			}
463	dl	1.22	}
464
465	tim	1.20
466	tim	1.15	/** Cannot instantiate. */
467			private Executors() {}
468	tim	1.1	}