--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/lang/ApplicationShutdownHooks.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2005-2006 Sun Microsystems, Inc.  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.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+package java.lang;
+
+import java.util.*;
+
+/*
+ * Class to track and run user level shutdown hooks registered through
+ * <tt>{@link Runtime#addShutdownHook Runtime.addShutdownHook}</tt>.
+ *
+ * @see java.lang.Runtime#addShutdownHook
+ * @see java.lang.Runtime#removeShutdownHook
+ */
+
+class ApplicationShutdownHooks implements Runnable {
+    private static ApplicationShutdownHooks instance = null;
+
+    /* The set of registered hooks */
+    private static IdentityHashMap<Thread, Thread> hooks = new IdentityHashMap<Thread, Thread>();
+
+    static synchronized ApplicationShutdownHooks hook() {
+        if (instance == null)
+            instance = new ApplicationShutdownHooks();
+
+        return instance;
+    }
+
+    private ApplicationShutdownHooks() {}
+
+    /* Add a new shutdown hook.  Checks the shutdown state and the hook itself,
+     * but does not do any security checks.
+     */
+    static synchronized void add(Thread hook) {
+        if(hooks == null)
+            throw new IllegalStateException("Shutdown in progress");
+
+        if (hook.isAlive())
+            throw new IllegalArgumentException("Hook already running");
+
+        if (hooks.containsKey(hook))
+            throw new IllegalArgumentException("Hook previously registered");
+
+        hooks.put(hook, hook);
+    }
+
+    /* Remove a previously-registered hook.  Like the add method, this method
+     * does not do any security checks.
+     */
+    static synchronized boolean remove(Thread hook) {
+        if(hooks == null)
+            throw new IllegalStateException("Shutdown in progress");
+
+        if (hook == null)
+            throw new NullPointerException();
+
+        return hooks.remove(hook) != null;
+    }
+
+    /* Iterates over all application hooks creating a new thread for each
+     * to run in. Hooks are run concurrently and this method waits for
+     * them to finish.
+     */
+    public void run() {
+        Collection<Thread> threads;
+        synchronized(ApplicationShutdownHooks.class) {
+            threads = hooks.keySet();
+            hooks = null;
+        }
+
+        for (Thread hook : threads) {
+            hook.start();
+        }
+        for (Thread hook : threads) {
+            try {
+                hook.join();
+            } catch (InterruptedException x) { }
+        }
+    }
+}