/*

 * Copyright 2005-2007 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.io;

import java.util.*;

import java.io.File;

/**

 * This class holds a set of filenames to be deleted on VM exit through a shutdown hook.

 * A set is used both to prevent double-insertion of the same file as well as offer

 * quick removal.

 */

class DeleteOnExitHook {

    private static DeleteOnExitHook instance = null;

    private static LinkedHashSet<String> files = new LinkedHashSet<String>();

    static DeleteOnExitHook hook() {

        if (instance == null)

            instance = new DeleteOnExitHook();

        return instance;

    }

    private DeleteOnExitHook() {}

    static synchronized void add(String file) {

        if(files == null)

            throw new IllegalStateException("Shutdown in progress");

        files.add(file);

    }

    void run() {

        LinkedHashSet<String> theFiles;

        synchronized (DeleteOnExitHook.class) {

            theFiles = files;

            files = null;

        }

        ArrayList<String> toBeDeleted = new ArrayList<String>(theFiles);

        // reverse the list to maintain previous jdk deletion order.

        // Last in first deleted.

        Collections.reverse(toBeDeleted);

        for (String filename : toBeDeleted) {

            (new File(filename)).delete();

        }

    }

}