util/concurrent/Future.java

/*
 * @(#)Future.java
 */

package java.util.concurrent;

/**
 * A <tt>Future</tt> represents the result of an asynchronous computation.
 * Methods are provided to check if the computation is complete,
 * to wait for its completion, and to retrieve the result of the
 * computation.  The result can only be retrieved when the computation
 * has completed.  The <tt>get</tt> method will block until the computation
 * has completed.  Once the computation has completed, the result cannot
 * be changed, nor can the computation be restarted or cancelled.
 *
 * <p>
 * <b>Sample Usage</b> (Note that the following classes are all
 * made-up.) <p>
 * <pre>
 * interface ArchiveSearcher { String search(String target); }
 * class App {
 *   Executor executor = ...
 *   ArchiveSearcher searcher = ...
 *   void showSearch(final String target) throws InterruptedException {
 *     Future&lt;String&gt; future =
 *       new FutureTask&lt;String&gt;(new Callable&lt;String&gt;() {
 *         public String call() {
 *           return searcher.search(target);
 *       }});
 *     executor.execute(future);
 *     displayOtherThings(); // do other things while searching
 *     try {
 *       displayText(future.get()); // use future
 *     } catch (ExecutionException ex) { cleanup(); return; }
 *   }
 * }
 * </pre>
 *
 * The {@link Executors} class contains more convenient methods 
 * for common usages. For example, the above explicit
 * construction could be replaced with:
 * <pre>
 * Future&lt;String&gt; future = Executors.execute(executor, 
 *    new Callable&lt;String&gt;() {
 *       public String call() {
 *         return searcher.search(target);
 *    }});
 * </pre>
 * @since 1.5
 * @see FutureTask
 * @see Executor
 *
 * @spec JSR-166
 * @revised $Date: 2003/08/19 15:04:57 $
 * @editor $Author: tim $
 * @author Doug Lea
 */
public interface Future<V> extends Cancellable {

    /**
     * Waits if necessary for computation to complete, and then
     * retrieves its result.
     *
     * @return computed result
     * @throws CancellationException here???
     * @throws ExecutionException if underlying computation threw an
     * exception
     * @throws InterruptedException if current thread was interrupted
     * while waiting
     */
    V get() throws InterruptedException, ExecutionException;

    /**
     * Waits if necessary for at most the given time for the computation
     * to complete, and then retrieves its result.
     *
     * @param timeout the maximum time to wait
     * @param granularity the time unit of the timeout argument
     * @return computed result
     * @throws ExecutionException if underlying computation threw an
     * exception
     * @throws InterruptedException if current thread was interrupted
     * while waiting
     * @throws TimeoutException if the wait timed out
     */
    V get(long timeout, TimeUnit granularity)
        throws InterruptedException, ExecutionException, TimeoutException;
}


Revision:	1.10
Committed:	Sun Aug 24 14:47:31 2003 UTC (20 years, 9 months ago) by dl
Branch:	MAIN
Changes since 1.9:	+12 -2 lines
Log Message:	Javadoc clarifications
#	Content
1	/*
2	* @(#)Future.java
3	*/
4
5	package java.util.concurrent;
6
7	/**
8	* A <tt>Future</tt> represents the result of an asynchronous computation.
9	* Methods are provided to check if the computation is complete,
10	* to wait for its completion, and to retrieve the result of the
11	* computation. The result can only be retrieved when the computation
12	* has completed. The <tt>get</tt> method will block until the computation
13	* has completed. Once the computation has completed, the result cannot
14	* be changed, nor can the computation be restarted or cancelled.
15	*
16	* <p>
17	* <b>Sample Usage</b> (Note that the following classes are all
18	* made-up.) <p>
19	* <pre>
20	* interface ArchiveSearcher { String search(String target); }
21	* class App {
22	* Executor executor = ...
23	* ArchiveSearcher searcher = ...
24	* void showSearch(final String target) throws InterruptedException {
25	* Future<String> future =
26	* new FutureTask<String>(new Callable<String>() {
27	* public String call() {
28	* return searcher.search(target);
29	* }});
30	* executor.execute(future);
31	* displayOtherThings(); // do other things while searching
32	* try {
33	* displayText(future.get()); // use future
34	* } catch (ExecutionException ex) { cleanup(); return; }
35	* }
36	* }
37	* </pre>
38	*
39	* The {@link Executors} class contains more convenient methods
40	* for common usages. For example, the above explicit
41	* construction could be replaced with:
42	* <pre>
43	* Future<String> future = Executors.execute(executor,
44	* new Callable<String>() {
45	* public String call() {
46	* return searcher.search(target);
47	* }});
48	* </pre>
49	* @since 1.5
50	* @see FutureTask
51	* @see Executor
52	*
53	* @spec JSR-166
54	* @revised $Date: 2003/08/19 15:04:57 $
55	* @editor $Author: tim $
56	* @author Doug Lea
57	*/
58	public interface Future<V> extends Cancellable {
59
60	/**
61	* Waits if necessary for computation to complete, and then
62	* retrieves its result.
63	*
64	* @return computed result
65	* @throws CancellationException here???
66	* @throws ExecutionException if underlying computation threw an
67	* exception
68	* @throws InterruptedException if current thread was interrupted
69	* while waiting
70	*/
71	V get() throws InterruptedException, ExecutionException;
72
73	/**
74	* Waits if necessary for at most the given time for the computation
75	* to complete, and then retrieves its result.
76	*
77	* @param timeout the maximum time to wait
78	* @param granularity the time unit of the timeout argument
79	* @return computed result
80	* @throws ExecutionException if underlying computation threw an
81	* exception
82	* @throws InterruptedException if current thread was interrupted
83	* while waiting
84	* @throws TimeoutException if the wait timed out
85	*/
86	V get(long timeout, TimeUnit granularity)
87	throws InterruptedException, ExecutionException, TimeoutException;
88	}
89
90
91