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My first initial commit with all of mine experimental changes.

Dmitry Kabak (userdima committed 13 years ago

Commit d37b88d1 parent 3f5b46618352 files · +2598093 −-8690Browse files

Showing the changes to java/pkg/java/nio/file/WatchKey.java (1 of 18352 files). Show all

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java/pkg/java/nio/file/WatchKey.java+150−0
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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.util.List;
29+
30+/**
31+ * A token representing the registration of a {@link Watchable watchable} object
32+ * with a {@link WatchService}.
33+ *
34+ * <p> A watch key is created when a watchable object is registered with a watch
35+ * service. The key remains {@link #isValid valid} until:
36+ * <ol>
37+ * <li> It is cancelled, explicitly, by invoking its {@link #cancel cancel}
38+ * method, or</li>
39+ * <li> Cancelled implicitly, because the object is no longer accessible,
40+ * or </li>
41+ * <li> By {@link WatchService#close closing} the watch service. </li>
42+ * </ol>
43+ *
44+ * <p> A watch key has a state. When initially created the key is said to be
45+ * <em>ready</em>. When an event is detected then the key is <em>signalled</em>
46+ * and queued so that it can be retrieved by invoking the watch service's {@link
47+ * WatchService#poll() poll} or {@link WatchService#take() take} methods. Once
48+ * signalled, a key remains in this state until its {@link #reset reset} method
49+ * is invoked to return the key to the ready state. Events detected while the
50+ * key is in the signalled state are queued but do not cause the key to be
51+ * re-queued for retrieval from the watch service. Events are retrieved by
52+ * invoking the key's {@link #pollEvents pollEvents} method. This method
53+ * retrieves and removes all events accumulated for the object. When initially
54+ * created, a watch key has no pending events. Typically events are retrieved
55+ * when the key is in the signalled state leading to the following idiom:
56+ *
57+ * <pre>
58+ * for (;;) {
59+ * // retrieve key
60+ * WatchKey key = watcher.take();
61+ *
62+ * // process events
63+ * for (WatchEvent&lt;?&gt; event: key.pollEvents()) {
64+ * :
65+ * }
66+ *
67+ * // reset the key
68+ * boolean valid = key.reset();
69+ * if (!valid) {
70+ * // object no longer registered
71+ * }
72+ * }
73+ * </pre>
74+ *
75+ * <p> Watch keys are safe for use by multiple concurrent threads. Where there
76+ * are several threads retrieving signalled keys from a watch service then care
77+ * should be taken to ensure that the {@code reset} method is only invoked after
78+ * the events for the object have been processed. This ensures that one thread
79+ * is processing the events for an object at any time.
80+ *
81+ * @since 1.7
82+ */
83+
84+public interface WatchKey {
85+
86+ /**
87+ * Tells whether or not this watch key is valid.
88+ *
89+ * <p> A watch key is valid upon creation and remains until it is cancelled,
90+ * or its watch service is closed.
91+ *
92+ * @return {@code true} if, and only if, this watch key is valid
93+ */
94+ boolean isValid();
95+
96+ /**
97+ * Retrieves and removes all pending events for this watch key, returning
98+ * a {@code List} of the events that were retrieved.
99+ *
100+ * <p> Note that this method does not wait if there are no events pending.
101+ *
102+ * @return the list of the events retrieved; may be empty
103+ */
104+ List<WatchEvent<?>> pollEvents();
105+
106+ /**
107+ * Resets this watch key.
108+ *
109+ * <p> If this watch key has been cancelled or this watch key is already in
110+ * the ready state then invoking this method has no effect. Otherwise
111+ * if there are pending events for the object then this watch key is
112+ * immediately re-queued to the watch service. If there are no pending
113+ * events then the watch key is put into the ready state and will remain in
114+ * that state until an event is detected or the watch key is cancelled.
115+ *
116+ * @return {@code true} if the watch key is valid and has been reset, and
117+ * {@code false} if the watch key could not be reset because it is
118+ * no longer {@link #isValid valid}
119+ */
120+ boolean reset();
121+
122+ /**
123+ * Cancels the registration with the watch service. Upon return the watch key
124+ * will be invalid. If the watch key is enqueued, waiting to be retrieved
125+ * from the watch service, then it will remain in the queue until it is
126+ * removed. Pending events, if any, remain pending and may be retrieved by
127+ * invoking the {@link #pollEvents pollEvents} method after the key is
128+ * cancelled.
129+ *
130+ * <p> If this watch key has already been cancelled then invoking this
131+ * method has no effect. Once cancelled, a watch key remains forever invalid.
132+ */
133+ void cancel();
134+
135+ /**
136+ * Returns the object for which this watch key was created. This method will
137+ * continue to return the object even after the key is cancelled.
138+ *
139+ * <p> As the {@code WatchService} is intended to map directly on to the
140+ * native file event notification facility (where available) then many of
141+ * details on how registered objects are watched is highly implementation
142+ * specific. When watching a directory for changes for example, and the
143+ * directory is moved or renamed in the file system, there is no guarantee
144+ * that the watch key will be cancelled and so the object returned by this
145+ * method may no longer be a valid path to the directory.
146+ *
147+ * @return the object for which this watch key was created
148+ */
149+ Watchable watchable();
150+}