Subversion Repositories openrisc

/*

 * 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;

import java.util.List;

import java.util.Collection;

import java.security.PrivilegedAction;

import java.security.PrivilegedExceptionAction;

/**

 * An {@link Executor} that provides methods to manage termination and

 * methods that can produce a {@link Future} for tracking progress of

 * one or more asynchronous tasks.

 *

 * <p>

 * 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.  An unused <tt>ExecutorService</tt> should be shut down

 * to allow reclamation of its resources.

 *

 * <p> Method <tt>submit</tt> extends base method {@link

 * Executor#execute} by creating and returning a {@link Future} that

 * can be used to cancel execution and/or wait for completion.

 * Methods <tt>invokeAny</tt> and <tt>invokeAll</tt> perform the most

 * commonly useful forms of bulk execution, executing a collection of

 * tasks and then waiting for at least one, or all, to

 * complete. (Class {@link ExecutorCompletionService} can be used to

 * write customized variants of these methods.)

 *

 * <p>The {@link Executors} class provides factory methods for the

 * executor services provided in this package.

 *

 * <h3>Usage Example</h3>

 *

 * Here is a sketch of a network service in which threads in a thread

 * pool service incoming requests. It uses the preconfigured {@link

 * Executors#newFixedThreadPool} factory method:

 *

 * <pre>

 * class NetworkService {

 *   private final ServerSocket serverSocket;

 *   private final ExecutorService pool;

 *

 *   public NetworkService(int port, int poolSize)

 *       throws IOException {

 *     serverSocket = new ServerSocket(port);

 *     pool = Executors.newFixedThreadPool(poolSize);

 *   }

 *

 *   public void serve() {

 *     try {

 *       for (;;) {

 *         pool.execute(new Handler(serverSocket.accept()));

 *       }

 *     } catch (IOException ex) {

 *       pool.shutdown();

 *     }

 *   }

 * }

 *

 * class Handler implements Runnable {

 *   private final Socket socket;

 *   Handler(Socket socket) { this.socket = socket; }

 *   public void run() {

 *     // read and service request

 *   }

 * }

 * </pre>

 *

 * <p>Memory consistency effects: Actions in a thread prior to the

 * submission of a {@code Runnable} or {@code Callable} task to an

 * {@code ExecutorService}

 * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>

 * any actions taken by that task, which in turn <i>happen-before</i> the

 * result is retrieved via {@code Future.get()}.

 *

 * @since 1.5

 * @author Doug Lea

 */

public interface ExecutorService extends Executor {

    /**

     * 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.

     *

     * @throws SecurityException if a security manager exists and

     *         shutting down this ExecutorService may manipulate

     *         threads that the caller is not permitted to modify

     *         because it does not hold {@link

     *         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,

     *         or the security manager's <tt>checkAccess</tt> method

     *         denies access.

     */

    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 any

     * task that fails to respond to interrupts may never terminate.

     *

     * @return list of tasks that never commenced execution

     * @throws SecurityException if a security manager exists and

     *         shutting down this ExecutorService may manipulate

     *         threads that the caller is not permitted to modify

     *         because it does not hold {@link

     *         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,

     *         or the security manager's <tt>checkAccess</tt> method

     *         denies access.

     */

    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;

    /**

     * Submits a value-returning task for execution and returns a

     * Future representing the pending results of the task. The

     * Future's <tt>get</tt> method will return the task's result upon

     * successful completion.

     *

     * <p>

     * If you would like to immediately block waiting

     * for a task, you can use constructions of the form

     * <tt>result = exec.submit(aCallable).get();</tt>

     *

     * <p> Note: The {@link Executors} class includes a set of methods

     * that can convert some other common closure-like objects,

     * for example, {@link java.security.PrivilegedAction} to

     * {@link Callable} form so they can be submitted.

     *

     * @param task the task to submit

     * @return a Future representing pending completion of the task

     * @throws RejectedExecutionException if the task cannot be

     *         scheduled for execution

     * @throws NullPointerException if the task is null

     */

    <T> Future<T> submit(Callable<T> task);

    /**

     * Submits a Runnable task for execution and returns a Future

     * representing that task. The Future's <tt>get</tt> method will

     * return the given result upon successful completion.

     *

     * @param task the task to submit

     * @param result the result to return

     * @return a Future representing pending completion of the task

     * @throws RejectedExecutionException if the task cannot be

     *         scheduled for execution

     * @throws NullPointerException if the task is null

     */

    <T> Future<T> submit(Runnable task, T result);

    /**

     * Submits a Runnable task for execution and returns a Future

     * representing that task. The Future's <tt>get</tt> method will

     * return <tt>null</tt> upon <em>successful</em> completion.

     *

     * @param task the task to submit

     * @return a Future representing pending completion of the task

     * @throws RejectedExecutionException if the task cannot be

     *         scheduled for execution

     * @throws NullPointerException if the task is null

     */

    Future<?> submit(Runnable task);

    /**

     * Executes the given tasks, returning a list of Futures holding

     * their status and results when all complete.

     * {@link Future#isDone} is <tt>true</tt> for each

     * element of the returned list.

     * Note that a <em>completed</em> task could have

     * terminated either normally or by throwing an exception.

     * The results of this method are undefined if the given

     * collection is modified while this operation is in progress.

     *

     * @param tasks the collection of tasks

     * @return A list of Futures representing the tasks, in the same

     *         sequential order as produced by the iterator for the

     *         given task list, each of which has completed.

     * @throws InterruptedException if interrupted while waiting, in

     *         which case unfinished tasks are cancelled.

     * @throws NullPointerException if tasks or any of its elements are <tt>null</tt>

     * @throws RejectedExecutionException if any task cannot be

     *         scheduled for execution

     */

    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)

        throws InterruptedException;

    /**

     * Executes the given tasks, returning a list of Futures holding

     * their status and results

     * when all complete or the timeout expires, whichever happens first.

     * {@link Future#isDone} is <tt>true</tt> for each

     * element of the returned list.

     * Upon return, tasks that have not completed are cancelled.

     * Note that a <em>completed</em> task could have

     * terminated either normally or by throwing an exception.

     * The results of this method are undefined if the given

     * collection is modified while this operation is in progress.

     *

     * @param tasks the collection of tasks

     * @param timeout the maximum time to wait

     * @param unit the time unit of the timeout argument

     * @return a list of Futures representing the tasks, in the same

     *         sequential order as produced by the iterator for the

     *         given task list. If the operation did not time out,

     *         each task will have completed. If it did time out, some

     *         of these tasks will not have completed.

     * @throws InterruptedException if interrupted while waiting, in

     *         which case unfinished tasks are cancelled

     * @throws NullPointerException if tasks, any of its elements, or

     *         unit are <tt>null</tt>

     * @throws RejectedExecutionException if any task cannot be scheduled

     *         for execution

     */

    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,

                                  long timeout, TimeUnit unit)

        throws InterruptedException;

    /**

     * Executes the given tasks, returning the result

     * of one that has completed successfully (i.e., without throwing

     * an exception), if any do. Upon normal or exceptional return,

     * tasks that have not completed are cancelled.

     * The results of this method are undefined if the given

     * collection is modified while this operation is in progress.

     *

     * @param tasks the collection of tasks

     * @return the result returned by one of the tasks

     * @throws InterruptedException if interrupted while waiting

     * @throws NullPointerException if tasks or any of its elements

     *         are <tt>null</tt>

     * @throws IllegalArgumentException if tasks is empty

     * @throws ExecutionException if no task successfully completes

     * @throws RejectedExecutionException if tasks cannot be scheduled

     *         for execution

     */

    <T> T invokeAny(Collection<? extends Callable<T>> tasks)

        throws InterruptedException, ExecutionException;

    /**

     * Executes the given tasks, returning the result

     * of one that has completed successfully (i.e., without throwing

     * an exception), if any do before the given timeout elapses.

     * Upon normal or exceptional return, tasks that have not

     * completed are cancelled.

     * The results of this method are undefined if the given

     * collection is modified while this operation is in progress.

     *

     * @param tasks the collection of tasks

     * @param timeout the maximum time to wait

     * @param unit the time unit of the timeout argument

     * @return the result returned by one of the tasks.

     * @throws InterruptedException if interrupted while waiting

     * @throws NullPointerException if tasks, any of its elements, or

     *         unit are <tt>null</tt>

     * @throws TimeoutException if the given timeout elapses before

     *         any task successfully completes

     * @throws ExecutionException if no task successfully completes

     * @throws RejectedExecutionException if tasks cannot be scheduled

     *         for execution

     */

    <T> T invokeAny(Collection<? extends Callable<T>> tasks,

                    long timeout, TimeUnit unit)

        throws InterruptedException, ExecutionException, TimeoutException;

}