/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. 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. Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.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
 * {@link Runtime#addShutdownHook Runtime.addShutdownHook}.
 *
 * @see java.lang.Runtime#addShutdownHook
 * @see java.lang.Runtime#removeShutdownHook
 */

class ApplicationShutdownHooks {
 /* The set of registered hooks */
 private static IdentityHashMap<Thread, Thread> hooks;
 static {
 try {
 Shutdown.add(1 /* shutdown hook invocation order */,
 false /* not registered if shutdown in progress */,
 new Runnable() {
 public void run() {
 runHooks();
 }
 }
 );
 hooks = new IdentityHashMap<>();
 } catch (IllegalStateException e) {
 // application shutdown hooks cannot be added if
 // shutdown is in progress.
 hooks = null;
 }
 }


 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.
 */
 static void runHooks() {
 Collection<Thread> threads;
 synchronized(ApplicationShutdownHooks.class) {
 threads = hooks.keySet();
 hooks = null;
 }

 for (Thread hook : threads) {
 hook.start();
 }
 for (Thread hook : threads) {
 while (true) {
 try {
 hook.join();
 break;
 } catch (InterruptedException ignored) {
 }
 }
 }
 }
}