/*

 * Copyright (c) 2007, 2011, Oracle and/or its affiliates. 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.  Oracle designates this

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

 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.nio.file;

import java.io.IOException;

/**

 * An object that may be registered with a watch service so that it can be

 * <em>watched</em> for changes and events.

 *

 * <p> This interface defines the {@link #register register} method to register

 * the object with a {@link WatchService} returning a {@link WatchKey} to

 * represent the registration. An object may be registered with more than one

 * watch service. Registration with a watch service is cancelled by invoking the

 * key's {@link WatchKey#cancel cancel} method.

 *

 * @since 1.7

 *

 * @see Path#register

 */

public interface Watchable {

    /**

     * Registers an object with a watch service.

     *

     * <p> If the file system object identified by this object is currently

     * registered with the watch service then the watch key, representing that

     * registration, is returned after changing the event set or modifiers to

     * those specified by the {@code events} and {@code modifiers} parameters.

     * Changing the event set does not cause pending events for the object to be

     * discarded. Objects are automatically registered for the {@link

     * StandardWatchEventKinds#OVERFLOW OVERFLOW} event. This event is not

     * required to be present in the array of events.

     *

     * <p> Otherwise the file system object has not yet been registered with the

     * given watch service, so it is registered and the resulting new key is

     * returned.

     *

     * <p> Implementations of this interface should specify the events they

     * support.

     *

     * @param   watcher

     *          the watch service to which this object is to be registered

     * @param   events

     *          the events for which this object should be registered

     * @param   modifiers

     *          the modifiers, if any, that modify how the object is registered

     *

     * @return  a key representing the registration of this object with the

     *          given watch service

     *

     * @throws  UnsupportedOperationException

     *          if unsupported events or modifiers are specified

     * @throws  IllegalArgumentException

     *          if an invalid of combination of events are modifiers are specified

     * @throws  ClosedWatchServiceException

     *          if the watch service is closed

     * @throws  IOException

     *          if an I/O error occurs

     * @throws  SecurityException

     *          if a security manager is installed and it denies an unspecified

     *          permission required to monitor this object. Implementations of

     *          this interface should specify the permission checks.

     */

    WatchKey register(WatchService watcher,

                      WatchEvent.Kind<?>[] events,

                      WatchEvent.Modifier... modifiers)

        throws IOException;

    /**

     * Registers an object with a watch service.

     *

     * <p> An invocation of this method behaves in exactly the same way as the

     * invocation

     * <pre>

     *     watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);

     * </pre>

     *

     * @param   watcher

     *          the watch service to which this object is to be registered

     * @param   events

     *          the events for which this object should be registered

     *

     * @return  a key representing the registration of this object with the

     *          given watch service

     *

     * @throws  UnsupportedOperationException

     *          if unsupported events are specified

     * @throws  IllegalArgumentException

     *          if an invalid of combination of events are specified

     * @throws  ClosedWatchServiceException

     *          if the watch service is closed

     * @throws  IOException

     *          if an I/O error occurs

     * @throws  SecurityException

     *          if a security manager is installed and it denies an unspecified

     *          permission required to monitor this object. Implementations of

     *          this interface should specify the permission checks.

     */

    WatchKey register(WatchService watcher, WatchEvent.Kind<?>... events)

        throws IOException;

}