1 /*
2 * Copyright 2005-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25 package java.lang;
26
27 import java.util;
28
29 /*
30 * Class to track and run user level shutdown hooks registered through
31 * <tt>{@link Runtime#addShutdownHook Runtime.addShutdownHook}</tt>.
32 *
33 * @see java.lang.Runtime#addShutdownHook
34 * @see java.lang.Runtime#removeShutdownHook
35 */
36
37 class ApplicationShutdownHooks implements Runnable {
38 private static ApplicationShutdownHooks instance = null;
39
40 /* The set of registered hooks */
41 private static IdentityHashMap<Thread, Thread> hooks = new IdentityHashMap<Thread, Thread>();
42
43 static synchronized ApplicationShutdownHooks hook() {
44 if (instance == null)
45 instance = new ApplicationShutdownHooks();
46
47 return instance;
48 }
49
50 private ApplicationShutdownHooks() {}
51
52 /* Add a new shutdown hook. Checks the shutdown state and the hook itself,
53 * but does not do any security checks.
54 */
55 static synchronized void add(Thread hook) {
56 if(hooks == null)
57 throw new IllegalStateException("Shutdown in progress");
58
59 if (hook.isAlive())
60 throw new IllegalArgumentException("Hook already running");
61
62 if (hooks.containsKey(hook))
63 throw new IllegalArgumentException("Hook previously registered");
64
65 hooks.put(hook, hook);
66 }
67
68 /* Remove a previously-registered hook. Like the add method, this method
69 * does not do any security checks.
70 */
71 static synchronized boolean remove(Thread hook) {
72 if(hooks == null)
73 throw new IllegalStateException("Shutdown in progress");
74
75 if (hook == null)
76 throw new NullPointerException();
77
78 return hooks.remove(hook) != null;
79 }
80
81 /* Iterates over all application hooks creating a new thread for each
82 * to run in. Hooks are run concurrently and this method waits for
83 * them to finish.
84 */
85 public void run() {
86 Collection<Thread> threads;
87 synchronized(ApplicationShutdownHooks.class) {
88 threads = hooks.keySet();
89 hooks = null;
90 }
91
92 for (Thread hook : threads) {
93 hook.start();
94 }
95 for (Thread hook : threads) {
96 try {
97 hook.join();
98 } catch (InterruptedException x) { }
99 }
100 }
101 }
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