/*
  * 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
- * <tt>{@link Runtime#addShutdownHook Runtime.addShutdownHook}</tt>.
+ * {@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) {
                 }
             }
         }
     }
 }