/*

 * Copyright 2007-2009 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package java.nio.file;

/**

 * An event or a repeated event for an object that is registered with a {@link

 * WatchService}.

 *

 * <p> An event is classified by its {@link #kind() kind} and has a {@link

 * #count() count} to indicate the number of times that the event has been

 * observed. This allows for efficient representation of repeated events. The

 * {@link #context() context} method returns any context associated with

 * the event. In the case of a repeated event then the context is the same for

 * all events.

 *

 * <p> Watch events are immutable and safe for use by multiple concurrent

 * threads.

 *

 * @param   <T>     The type of the context object associated with the event

 *

 * @since 1.7

 */

public abstract class WatchEvent<T> {

    /**

     * An event kind, for the purposes of identification.

     *

     * @since 1.7

     * @see StandardWatchEventKind

     */

    public static interface Kind<T> {

        /**

         * Returns the name of the event kind.

         */

        String name();

        /**

         * Returns the type of the {@link WatchEvent#context context} value.

         */

        Class<T> type();

    }

    /**

     * Initializes a new instance of this class.

     */

    protected WatchEvent() { }

    /**

     * An event modifier that qualifies how a {@link Watchable} is registered

     * with a {@link WatchService}.

     *

     * <p> This release does not define any <em>standard</em> modifiers.

     *

     * @since 1.7

     * @see Watchable#register

     */

    public static interface Modifier {

        /**

         * Returns the name of the modifier.

         */

        String name();

    }

    /**

     * Returns the event kind.

     *

     * @return  The event kind

     */

    public abstract Kind<T> kind();

    /**

     * Returns the event count. If the event count is greater than {@code 1}

     * then this is a repeated event.

     *

     * @return  The event count

     */

    public abstract int count();

    /**

     * Returns the context for the event.

     *

     * <p> In the case of {@link StandardWatchEventKind#ENTRY_CREATE ENTRY_CREATE},

     * {@link StandardWatchEventKind#ENTRY_DELETE ENTRY_DELETE}, and {@link

     * StandardWatchEventKind#ENTRY_MODIFY ENTRY_MODIFY} events the context is

     * a {@code Path} that is the {@link Path#relativize relative} path between

     * the directory registered with the watch service, and the entry that is

     * created, deleted, or modified.

     *

     * @return  The event context; may be {@code null}

     */

    public abstract T context();

}