util/concurrent/ExecutorService.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.List;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;

/**
 * An <tt>Executor</tt> that provides methods to manage termination
 * and those that can produce a {@link Future} for tracking
 * progress of an asynchronous task.
 * An <tt>ExecutorService</tt> can be shut down, which will cause it
 * to stop accepting new tasks.  After being shut down, the executor
 * will eventually terminate, at which point no tasks are actively
 * executing, no tasks are awaiting execution, and no new tasks can be
 * submitted.
 *
 * <p>The {@link Executors} class provides factory methods for the
 * executor services provided in this package.
 *
 * @since 1.5
 * @author Doug Lea
 */
public interface ExecutorService extends Executor {

    /**
     * Submits a Runnable task for execution and returns a Future 
     * representing that task.
     *
     * @param task the task to submit
     * @return a Future representing pending completion of the task,
     * and whose <tt>get()</tt> method will return an arbitrary value 
     * upon completion
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     */
    Future<?> submit(Runnable task);

    /**
     * Submits a value-returning task for execution and returns a Future
     * representing the pending results of the task.
     *
     * @param task the task to submit
     * @return a Future representing pending completion of the task
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution
     */
    <T> Future<T> submit(Callable<T> task);

    /**
     * Executes a Runnable task and blocks until it completes normally
     * or throws an exception.
     *
     * @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
     */
    void invoke(Runnable task) throws ExecutionException, InterruptedException;

    /**
     * Executes a value-returning task and blocks until it returns a
     * value or throws an exception.
     *
     * @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
     */
    <T> T invoke(Callable<T> task) throws ExecutionException, InterruptedException;


    /**
     * Submits a privileged action for execution under the current 
     * access control context and returns a Future representing the 
     * pending result object of that action.
     *
     * @param action the action to submit
     * @return a Future representing pending completion of the action
     * @throws RejectedExecutionException if action cannot be scheduled
     * for execution
     */
    Future<Object> submit(PrivilegedAction action);

    /**
     * Submits a privileged exception action for execution under the current 
     * access control context and returns a Future representing the pending 
     * result object of that action.
     *
     * @param action the action to submit
     * @return a Future representing pending completion of the action
     * @throws RejectedExecutionException if action cannot be scheduled
     * for execution
     */
    Future<Object> submit(PrivilegedExceptionAction action);
    

    /**
     * Initiates an orderly shutdown in which previously submitted
     * tasks are executed, but no new tasks will be
     * accepted. Invocation has no additional effect if already shut
     * down.
     *
     */
    void shutdown();

    /**
     * Attempts to stop all actively executing tasks, halts the
     * processing of waiting tasks, and returns a list of the tasks that were
     * awaiting execution. 
     *  
     * <p>There are no guarantees beyond best-effort attempts to stop
     * processing actively executing tasks.  For example, typical
     * implementations will cancel via {@link Thread#interrupt}, so if any
     * tasks mask or fail to respond to interrupts, they may never terminate.
     *
     * @return list of tasks that never commenced execution
     */
    List<Runnable> shutdownNow();

    /**
     * Returns <tt>true</tt> if this executor has been shut down.
     *
     * @return <tt>true</tt> if this executor has been shut down
     */
    boolean isShutdown();

    /**
     * Returns <tt>true</tt> if all tasks have completed following shut down.
     * Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
     * either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
     *
     * @return <tt>true</tt> if all tasks have completed following shut down
     */
    boolean isTerminated();

    /**
     * Blocks until all tasks have completed execution after a shutdown
     * request, or the timeout occurs, or the current thread is
     * interrupted, whichever happens first.
     *
     * @param timeout the maximum time to wait
     * @param unit the time unit of the timeout argument
     * @return <tt>true</tt> if this executor terminated and <tt>false</tt>
     * if the timeout elapsed before termination
     * @throws InterruptedException if interrupted while waiting
     */
    boolean awaitTermination(long timeout, TimeUnit unit)
        throws InterruptedException;

}
Revision:	1.10
Committed:	Wed Dec 10 13:00:13 2003 UTC (20 years, 6 months ago) by dl
Branch:	MAIN
Changes since 1.9:	+3 -1 lines
Log Message:	Documentation updates
#	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
9	import java.util.List;
10	import java.security.PrivilegedAction;
11	import java.security.PrivilegedExceptionAction;
12
13	/**
14	* An <tt>Executor</tt> that provides methods to manage termination
15	* and those that can produce a {@link Future} for tracking
16	* progress of an asynchronous task.
17	* An <tt>ExecutorService</tt> can be shut down, which will cause it
18	* to stop accepting new tasks. After being shut down, the executor
19	* will eventually terminate, at which point no tasks are actively
20	* executing, no tasks are awaiting execution, and no new tasks can be
21	* submitted.
22	*
23	* <p>The {@link Executors} class provides factory methods for the
24	* executor services provided in this package.
25	*
26	* @since 1.5
27	* @author Doug Lea
28	*/
29	public interface ExecutorService extends Executor {
30
31	/**
32	* Submits a Runnable task for execution and returns a Future
33	* representing that task.
34	*
35	* @param task the task to submit
36	* @return a Future representing pending completion of the task,
37	* and whose <tt>get()</tt> method will return an arbitrary value
38	* upon completion
39	* @throws RejectedExecutionException if task cannot be scheduled
40	* for execution
41	*/
42	Future<?> submit(Runnable task);
43
44	/**
45	* Submits a value-returning task for execution and returns a Future
46	* representing the pending results of the task.
47	*
48	* @param task the task to submit
49	* @return a Future representing pending completion of the task
50	* @throws RejectedExecutionException if task cannot be scheduled
51	* for execution
52	*/
53	<T> Future<T> submit(Callable<T> task);
54
55	/**
56	* Executes a Runnable task and blocks until it completes normally
57	* or throws an exception.
58	*
59	* @param task the task to submit
60	* @throws RejectedExecutionException if task cannot be scheduled
61	* for execution
62	* @throws ExecutionException if the task encountered an exception
63	* while executing
64	*/
65	void invoke(Runnable task) throws ExecutionException, InterruptedException;
66
67	/**
68	* Executes a value-returning task and blocks until it returns a
69	* value or throws an exception.
70	*
71	* @param task the task to submit
72	* @return a Future representing pending completion of the task
73	* @throws RejectedExecutionException if task cannot be scheduled
74	* for execution
75	* @throws InterruptedException if interrupted while waiting for
76	* completion
77	* @throws ExecutionException if the task encountered an exception
78	* while executing
79	*/
80	<T> T invoke(Callable<T> task) throws ExecutionException, InterruptedException;
81
82
83	/**
84	* Submits a privileged action for execution under the current
85	* access control context and returns a Future representing the
86	* pending result object of that action.
87	*
88	* @param action the action to submit
89	* @return a Future representing pending completion of the action
90	* @throws RejectedExecutionException if action cannot be scheduled
91	* for execution
92	*/
93	Future<Object> submit(PrivilegedAction action);
94
95	/**
96	* Submits a privileged exception action for execution under the current
97	* access control context and returns a Future representing the pending
98	* result object of that action.
99	*
100	* @param action the action to submit
101	* @return a Future representing pending completion of the action
102	* @throws RejectedExecutionException if action cannot be scheduled
103	* for execution
104	*/
105	Future<Object> submit(PrivilegedExceptionAction action);
106
107
108	/**
109	* Initiates an orderly shutdown in which previously submitted
110	* tasks are executed, but no new tasks will be
111	* accepted. Invocation has no additional effect if already shut
112	* down.
113	*
114	*/
115	void shutdown();
116
117	/**
118	* Attempts to stop all actively executing tasks, halts the
119	* processing of waiting tasks, and returns a list of the tasks that were
120	* awaiting execution.
121	*
122	* <p>There are no guarantees beyond best-effort attempts to stop
123	* processing actively executing tasks. For example, typical
124	* implementations will cancel via {@link Thread#interrupt}, so if any
125	* tasks mask or fail to respond to interrupts, they may never terminate.
126	*
127	* @return list of tasks that never commenced execution
128	*/
129	List<Runnable> shutdownNow();
130
131	/**
132	* Returns <tt>true</tt> if this executor has been shut down.
133	*
134	* @return <tt>true</tt> if this executor has been shut down
135	*/
136	boolean isShutdown();
137
138	/**
139	* Returns <tt>true</tt> if all tasks have completed following shut down.
140	* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
141	* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
142	*
143	* @return <tt>true</tt> if all tasks have completed following shut down
144	*/
145	boolean isTerminated();
146
147	/**
148	* Blocks until all tasks have completed execution after a shutdown
149	* request, or the timeout occurs, or the current thread is
150	* interrupted, whichever happens first.
151	*
152	* @param timeout the maximum time to wait
153	* @param unit the time unit of the timeout argument
154	* @return <tt>true</tt> if this executor terminated and <tt>false</tt>
155	* if the timeout elapsed before termination
156	* @throws InterruptedException if interrupted while waiting
157	*/
158	boolean awaitTermination(long timeout, TimeUnit unit)
159	throws InterruptedException;
160
161	}