/* * 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>. * * @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) {            try {                hook.join();            } catch (InterruptedException x) { }        }    }}