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
#	User	Rev	Content
1	dl	1.1	/*
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	tim	1.8	import java.security.PrivilegedAction;
11			import java.security.PrivilegedExceptionAction;
12	dl	1.1
13			/**
14	dl	1.10	* 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	dl	1.7	* 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	dl	1.1	* executing, no tasks are awaiting execution, and no new tasks can be
21			* submitted.
22			*
23	dl	1.7	* <p>The {@link Executors} class provides factory methods for the
24			* executor services provided in this package.
25	dl	1.1	*
26			* @since 1.5
27	dl	1.5	* @author Doug Lea
28	dl	1.1	*/
29			public interface ExecutorService extends Executor {
30	tim	1.8
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	dl	1.1
108			/**
109	dl	1.6	* 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	dl	1.1	*
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	tim	1.9	List<Runnable> shutdownNow();
130	dl	1.1
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	dl	1.3
161	dl	1.1	}