util/concurrent/Executor.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

package java.util.concurrent;

/**
 * An object that executes submitted {@link Runnable} tasks. This
 * interface provides a way of decoupling task submission from the
 * mechanics of how each task will be run, including details of thread
 * use, scheduling, etc.  In the simplest case, an executor can run
 * the submitted task immediately in the caller's thread:
 *
 * <pre>
 * class DirectExecutor implements Executor {
 *     public void execute(Runnable r) {
 *         r.run();
 *     }
 * }</pre>
 *
 * However, tasks are typically executed in a different thread than
 * the caller's thread.  The executor below spawns a new thread for
 * each task.
 *
 * <pre>
 * class ThreadPerTaskExecutor implements Executor {
 *     public void execute(Runnable r) {
 *         new Thread(r).start();
 *     }
 * }</pre>
 *
 * Most <tt>Executor</tt> implementations will impose some sort of
 * limitation on how and when tasks are scheduled.  The executor below
 * serializes the submission of tasks to a second executor,
 * illustrating a composite executor.
 *
 * <pre>
 * class SerialExecutor implements Executor {
 *     final Queue&lt;Runnable&gt; tasks = new LinkedBlockingQueue&lt;Runnable&gt;();
 *     final Executor executor;
 *     Runnable active;
 *
 *     SerialExecutor(Executor executor) {
 *         this.executor = executor;
 *     }
 *
 *     public synchronized void execute(final Runnable r) {
 *         tasks.offer(new Runnable() {
 *             public void run() {
 *                 try {
 *                     r.run();
 *                 } finally {
 *                     scheduleNext();
 *                 }
 *             }
 *         });
 *         if (active == null) {
 *             scheduleNext();
 *         }
 *     }
 *
 *     protected synchronized void scheduleNext() {
 *         if ((active = tasks.poll()) != null) {
 *             executor.execute(active);
 *         }
 *     }
 * }</pre>
 *
 * The <tt>Executor</tt> implementations provided in this package
 * implement {@link ExecutorService}, which is a more extensive
 * interface.  The {@link ThreadPoolExecutor} class provides an
 * extensible thread pool implementation. The {@link Executors} class
 * provides convenient factory methods for these Executors.
 *
 * @since 1.5
 * @author Doug Lea
 */
public interface Executor {

    /**
     * Executes the given command at some time in the future.  The command
     * may execute in a new thread, in a pooled thread, or in the calling
     * thread, at the discretion of the <tt>Executor</tt> implementation.
     *
     * @param command the runnable task
     * @throws RejectedExecutionException if this task cannot be
     * accepted for execution.
     * @throws NullPointerException if command is null
     */
    void execute(Runnable command);
}
Revision:	1.15
Committed:	Sat Dec 27 19:26:25 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.14:	+2 -2 lines
Log Message:	Headers reference Creative Commons
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain, as explained at
4	* http://creativecommons.org/licenses/publicdomain
5	*/
6
7	package java.util.concurrent;
8
9	/**
10	* An object that executes submitted {@link Runnable} tasks. This
11	* interface provides a way of decoupling task submission from the
12	* mechanics of how each task will be run, including details of thread
13	* use, scheduling, etc. In the simplest case, an executor can run
14	* the submitted task immediately in the caller's thread:
15	*
16	* <pre>
17	* class DirectExecutor implements Executor {
18	* public void execute(Runnable r) {
19	* r.run();
20	* }
21	* }</pre>
22	*
23	* However, tasks are typically executed in a different thread than
24	* the caller's thread. The executor below spawns a new thread for
25	* each task.
26	*
27	* <pre>
28	* class ThreadPerTaskExecutor implements Executor {
29	* public void execute(Runnable r) {
30	* new Thread(r).start();
31	* }
32	* }</pre>
33	*
34	* Most <tt>Executor</tt> implementations will impose some sort of
35	* limitation on how and when tasks are scheduled. The executor below
36	* serializes the submission of tasks to a second executor,
37	* illustrating a composite executor.
38	*
39	* <pre>
40	* class SerialExecutor implements Executor {
41	* final Queue<Runnable> tasks = new LinkedBlockingQueue<Runnable>();
42	* final Executor executor;
43	* Runnable active;
44	*
45	* SerialExecutor(Executor executor) {
46	* this.executor = executor;
47	* }
48	*
49	* public synchronized void execute(final Runnable r) {
50	* tasks.offer(new Runnable() {
51	* public void run() {
52	* try {
53	* r.run();
54	* } finally {
55	* scheduleNext();
56	* }
57	* }
58	* });
59	* if (active == null) {
60	* scheduleNext();
61	* }
62	* }
63	*
64	* protected synchronized void scheduleNext() {
65	* if ((active = tasks.poll()) != null) {
66	* executor.execute(active);
67	* }
68	* }
69	* }</pre>
70	*
71	* The <tt>Executor</tt> implementations provided in this package
72	* implement {@link ExecutorService}, which is a more extensive
73	* interface. The {@link ThreadPoolExecutor} class provides an
74	* extensible thread pool implementation. The {@link Executors} class
75	* provides convenient factory methods for these Executors.
76	*
77	* @since 1.5
78	* @author Doug Lea
79	*/
80	public interface Executor {
81
82	/**
83	* Executes the given command at some time in the future. The command
84	* may execute in a new thread, in a pooled thread, or in the calling
85	* thread, at the discretion of the <tt>Executor</tt> implementation.
86	*
87	* @param command the runnable task
88	* @throws RejectedExecutionException if this task cannot be
89	* accepted for execution.
90	* @throws NullPointerException if command is null
91	*/
92	void execute(Runnable command);
93	}