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.*;

/**
 * Factory and utility methods for the <tt>Executor</tt> classes
 * defined in <tt>java.util.concurrent</tt>.
 *
 * @since 1.5
 * @see Executor
 * @see ExecutorService
 * @see Future
 *
 * @spec JSR-166
 * @revised $Date: 2003/08/19 15:04:57 $
 * @editor $Author: tim $
 * @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 Cancellable representing that
     * task.
     *
     * @param executor the Executor to which the task will be submitted
     * @param task the task to submit
     * @return a Cancellable representing pending completion of the task
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     */
    public static Cancellable 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
     */
    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
     */
    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();
    }

    
    /** Cannot instantiate. */
    private Executors() {}
}
Revision:	1.16
Committed:	Sun Aug 24 23:32:25 2003 UTC (20 years, 9 months ago) by dl
Branch:	MAIN
Changes since 1.15:	+11 -5 lines
Log Message:	Kill ScheduledExecutor Date methods; Documentation clarifications
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain. Use, modify, and
4	* redistribute this code in any way without acknowledgement.
5	*/
6
7	package java.util.concurrent;
8	import java.util.*;
9
10	/**
11	* Factory and utility methods for the <tt>Executor</tt> classes
12	* defined in <tt>java.util.concurrent</tt>.
13	*
14	* @since 1.5
15	* @see Executor
16	* @see ExecutorService
17	* @see Future
18	*
19	* @spec JSR-166
20	* @revised $Date: 2003/08/19 15:04:57 $
21	* @editor $Author: tim $
22	* @author Doug Lea
23	*/
24	public class Executors {
25
26	/**
27	* A wrapper class that exposes only the ExecutorService methods
28	* of an implementation.
29	*/
30	private static class DelegatedExecutorService implements ExecutorService {
31	private final ExecutorService e;
32	DelegatedExecutorService(ExecutorService executor) { e = executor; }
33	public void execute(Runnable command) { e.execute(command); }
34	public void shutdown() { e.shutdown(); }
35	public List shutdownNow() { return e.shutdownNow(); }
36	public boolean isShutdown() { return e.isShutdown(); }
37	public boolean isTerminated() { return e.isTerminated(); }
38	public boolean awaitTermination(long timeout, TimeUnit unit)
39	throws InterruptedException {
40	return e.awaitTermination(timeout, unit);
41	}
42	}
43
44	/**
45	* Creates a thread pool that reuses a fixed set of threads
46	* operating off a shared unbounded queue. If any thread
47	* terminates due to a failure during execution prior to shutdown,
48	* a new one will take its place if needed to execute subsequent
49	* tasks.
50	*
51	* @param nThreads the number of threads in the pool
52	* @return the newly created thread pool
53	*/
54	public static ExecutorService newFixedThreadPool(int nThreads) {
55	return new DelegatedExecutorService
56	(new ThreadPoolExecutor(nThreads, nThreads,
57	0L, TimeUnit.MILLISECONDS,
58	new LinkedBlockingQueue<Runnable>()));
59	}
60
61	/**
62	* Creates a thread pool that reuses a fixed set of threads
63	* operating off a shared unbounded queue, using the provided
64	* ThreadFactory to create new threads when needed.
65	*
66	* @param nThreads the number of threads in the pool
67	* @param threadFactory the factory to use when creating new threads
68	* @return the newly created thread pool
69	*/
70	public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
71	return new DelegatedExecutorService
72	(new ThreadPoolExecutor(nThreads, nThreads,
73	0L, TimeUnit.MILLISECONDS,
74	new LinkedBlockingQueue<Runnable>(),
75	threadFactory));
76	}
77
78	/**
79	* Creates an Executor that uses a single worker thread operating
80	* off an unbounded queue. (Note however that if this single
81	* thread terminates due to a failure during execution prior to
82	* shutdown, a new one will take its place if needed to execute
83	* subsequent tasks.) Tasks are guaranteed to execute
84	* sequentially, and no more than one task will be active at any
85	* given time. This method is equivalent in effect to
86	*<tt>new FixedThreadPool(1)</tt>.
87	*
88	* @return the newly-created single-threaded Executor
89	*/
90	public static ExecutorService newSingleThreadExecutor() {
91	return new DelegatedExecutorService
92	(new ThreadPoolExecutor(1, 1,
93	0L, TimeUnit.MILLISECONDS,
94	new LinkedBlockingQueue<Runnable>()));
95	}
96
97	/**
98	* Creates an Executor that uses a single worker thread operating
99	* off an unbounded queue, and uses the provided ThreadFactory to
100	* create new threads when needed.
101	* @param threadFactory the factory to use when creating new
102	* threads
103	*
104	* @return the newly-created single-threaded Executor
105	*/
106	public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) {
107	return new DelegatedExecutorService
108	(new ThreadPoolExecutor(1, 1,
109	0L, TimeUnit.MILLISECONDS,
110	new LinkedBlockingQueue<Runnable>(),
111	threadFactory));
112	}
113
114	/**
115	* Creates a thread pool that creates new threads as needed, but
116	* will reuse previously constructed threads when they are
117	* available. These pools will typically improve the performance
118	* of programs that execute many short-lived asynchronous tasks.
119	* Calls to <tt>execute</tt> will reuse previously constructed
120	* threads if available. If no existing thread is available, a new
121	* thread will be created and added to the pool. Threads that have
122	* not been used for sixty seconds are terminated and removed from
123	* the cache. Thus, a pool that remains idle for long enough will
124	* not consume any resources. Note that pools with similar
125	* properties but different details (for example, timeout parameters)
126	* may be created using {@link ThreadPoolExecutor} constructors.
127	*
128	* @return the newly created thread pool
129	*/
130	public static ExecutorService newCachedThreadPool() {
131	return new DelegatedExecutorService
132	(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
133	60, TimeUnit.SECONDS,
134	new SynchronousQueue<Runnable>()));
135	}
136
137	/**
138	* Creates a thread pool that creates new threads as needed, but
139	* will reuse previously constructed threads when they are
140	* available, and uses the provided
141	* ThreadFactory to create new threads when needed.
142	* @param threadFactory the factory to use when creating new threads
143	* @return the newly created thread pool
144	*/
145	public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
146	return new DelegatedExecutorService
147	(new ThreadPoolExecutor(0, Integer.MAX_VALUE,
148	60, TimeUnit.SECONDS,
149	new SynchronousQueue<Runnable>(),
150	threadFactory));
151	}
152
153	/**
154	* Executes a Runnable task and returns a Cancellable representing that
155	* task.
156	*
157	* @param executor the Executor to which the task will be submitted
158	* @param task the task to submit
159	* @return a Cancellable representing pending completion of the task
160	* @throws RejectedExecutionException if task cannot be scheduled
161	* for execution
162	*/
163	public static Cancellable execute(Executor executor, Runnable task) {
164	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
165	executor.execute(ftask);
166	return ftask;
167	}
168
169	/**
170	* Executes a Runnable task and returns a Future representing that
171	* task.
172	*
173	* @param executor the Executor to which the task will be submitted
174	* @param task the task to submit
175	* @param value the value which will become the return value of
176	* the task upon task completion
177	* @return a Future representing pending completion of the task
178	* @throws RejectedExecutionException if task cannot be scheduled
179	* for execution
180	*/
181	public static <T> Future<T> execute(Executor executor, Runnable task, T value) {
182	FutureTask<T> ftask = new FutureTask<T>(task, value);
183	executor.execute(ftask);
184	return ftask;
185	}
186
187	/**
188	* Executes a value-returning task and returns a Future
189	* representing the pending results of the task.
190	*
191	* @param executor the Executor to which the task will be submitted
192	* @param task the task to submit
193	* @return a Future representing pending completion of the task
194	* @throws RejectedExecutionException if task cannot be scheduled
195	* for execution
196	*/
197	public static <T> Future<T> execute(Executor executor, Callable<T> task) {
198	FutureTask<T> ftask = new FutureTask<T>(task);
199	executor.execute(ftask);
200	return ftask;
201	}
202
203	/**
204	* Executes a Runnable task and blocks until it completes normally
205	* or throws an exception.
206	*
207	* @param executor the Executor to which the task will be submitted
208	* @param task the task to submit
209	* @throws RejectedExecutionException if task cannot be scheduled
210	* for execution
211	*/
212	public static void invoke(Executor executor, Runnable task)
213	throws ExecutionException, InterruptedException {
214	FutureTask<Boolean> ftask = new FutureTask<Boolean>(task, Boolean.TRUE);
215	executor.execute(ftask);
216	ftask.get();
217	}
218
219	/**
220	* Executes a value-returning task and blocks until it returns a
221	* value or throws an exception.
222	*
223	* @param executor the Executor to which the task will be submitted
224	* @param task the task to submit
225	* @return a Future representing pending completion of the task
226	* @throws RejectedExecutionException if task cannot be scheduled
227	* for execution
228	* @throws InterruptedException if interrupted while waiting for
229	* completion
230	*/
231	public static <T> T invoke(Executor executor, Callable<T> task)
232	throws ExecutionException, InterruptedException {
233	FutureTask<T> ftask = new FutureTask<T>(task);
234	executor.execute(ftask);
235	return ftask.get();
236	}
237
238
239	/** Cannot instantiate. */
240	private Executors() {}
241	}