1/*
2 * Copyright (c) 2007, 2013, 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
26package java.nio.file;
27
28/**
29 * An event or a repeated event for an object that is registered with a {@link
30 * WatchService}.
31 *
32 * <p> An event is classified by its {@link #kind() kind} and has a {@link
33 * #count() count} to indicate the number of times that the event has been
34 * observed. This allows for efficient representation of repeated events. The
35 * {@link #context() context} method returns any context associated with
36 * the event. In the case of a repeated event then the context is the same for
37 * all events.
38 *
39 * <p> Watch events are immutable and safe for use by multiple concurrent
40 * threads.
41 *
42 * @param   <T>     The type of the context object associated with the event
43 *
44 * @since 1.7
45 */
46
47public interface WatchEvent<T> {
48
49    /**
50     * An event kind, for the purposes of identification.
51     *
52     * @since 1.7
53     * @see StandardWatchEventKinds
54     */
55    public static interface Kind<T> {
56        /**
57         * Returns the name of the event kind.
58         *
59         * @return the name of the event kind
60         */
61        String name();
62
63        /**
64         * Returns the type of the {@link WatchEvent#context context} value.
65         *
66         *
67         * @return the type of the context value
68         */
69        Class<T> type();
70    }
71
72    /**
73     * An event modifier that qualifies how a {@link Watchable} is registered
74     * with a {@link WatchService}.
75     *
76     * <p> This release does not define any <em>standard</em> modifiers.
77     *
78     * @since 1.7
79     * @see Watchable#register
80     */
81    public static interface Modifier {
82        /**
83         * Returns the name of the modifier.
84         *
85         * @return the name of the modifier
86         */
87        String name();
88    }
89
90    /**
91     * Returns the event kind.
92     *
93     * @return  the event kind
94     */
95    Kind<T> kind();
96
97    /**
98     * Returns the event count. If the event count is greater than {@code 1}
99     * then this is a repeated event.
100     *
101     * @return  the event count
102     */
103    int count();
104
105    /**
106     * Returns the context for the event.
107     *
108     * <p> In the case of {@link StandardWatchEventKinds#ENTRY_CREATE ENTRY_CREATE},
109     * {@link StandardWatchEventKinds#ENTRY_DELETE ENTRY_DELETE}, and {@link
110     * StandardWatchEventKinds#ENTRY_MODIFY ENTRY_MODIFY} events the context is
111     * a {@code Path} that is the {@link Path#relativize relative} path between
112     * the directory registered with the watch service, and the entry that is
113     * created, deleted, or modified.
114     *
115     * @return  the event context; may be {@code null}
116     */
117    T context();
118}
119