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1   /*
2    * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22   * or visit www.oracle.com if you need additional information or have any
23   * questions.
24   */
25  
26  package java.nio.file;
27  
28  import java.io.IOException;
29  
30  /**
31   * An object that may be registered with a watch service so that it can be
32   * <em>watched</em> for changes and events.
33   *
34   * <p> This interface defines the {@link #register register} method to register
35   * the object with a {@link WatchService} returning a {@link WatchKey} to
36   * represent the registration. An object may be registered with more than one
37   * watch service. Registration with a watch service is cancelled by invoking the
38   * key's {@link WatchKey#cancel cancel} method.
39   *
40   * @since 1.7
41   *
42   * @see Path#register
43   */
44  
45  public interface Watchable {
46  
47      /**
48       * Registers an object with a watch service.
49       *
50       * <p> If the file system object identified by this object is currently
51       * registered with the watch service then the watch key, representing that
52       * registration, is returned after changing the event set or modifiers to
53       * those specified by the {@code events} and {@code modifiers} parameters.
54       * Changing the event set does not cause pending events for the object to be
55       * discarded. Objects are automatically registered for the {@link
56       * StandardWatchEventKinds#OVERFLOW OVERFLOW} event. This event is not
57       * required to be present in the array of events.
58       *
59       * <p> Otherwise the file system object has not yet been registered with the
60       * given watch service, so it is registered and the resulting new key is
61       * returned.
62       *
63       * <p> Implementations of this interface should specify the events they
64       * support.
65       *
66       * @param   watcher
67       *          the watch service to which this object is to be registered
68       * @param   events
69       *          the events for which this object should be registered
70       * @param   modifiers
71       *          the modifiers, if any, that modify how the object is registered
72       *
73       * @return  a key representing the registration of this object with the
74       *          given watch service
75       *
76       * @throws  UnsupportedOperationException
77       *          if unsupported events or modifiers are specified
78       * @throws  IllegalArgumentException
79       *          if an invalid of combination of events are modifiers are specified
80       * @throws  ClosedWatchServiceException
81       *          if the watch service is closed
82       * @throws  IOException
83       *          if an I/O error occurs
84       * @throws  SecurityException
85       *          if a security manager is installed and it denies an unspecified
86       *          permission required to monitor this object. Implementations of
87       *          this interface should specify the permission checks.
88       */
89      WatchKey register(WatchService watcher,
90                        WatchEvent.Kind<?>[] events,
91                        WatchEvent.Modifier... modifiers)
92          throws IOException;
93  
94  
95      /**
96       * Registers an object with a watch service.
97       *
98       * <p> An invocation of this method behaves in exactly the same way as the
99       * invocation
100      * <pre>
101      *     watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
102      * </pre>
103      *
104      * @param   watcher
105      *          the watch service to which this object is to be registered
106      * @param   events
107      *          the events for which this object should be registered
108      *
109      * @return  a key representing the registration of this object with the
110      *          given watch service
111      *
112      * @throws  UnsupportedOperationException
113      *          if unsupported events are specified
114      * @throws  IllegalArgumentException
115      *          if an invalid of combination of events are specified
116      * @throws  ClosedWatchServiceException
117      *          if the watch service is closed
118      * @throws  IOException
119      *          if an I/O error occurs
120      * @throws  SecurityException
121      *          if a security manager is installed and it denies an unspecified
122      *          permission required to monitor this object. Implementations of
123      *          this interface should specify the permission checks.
124      */
125     WatchKey register(WatchService watcher, WatchEvent.Kind<?>... events)
126         throws IOException;
127 }