/*
 * Copyright (c) 2005, 2007, 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.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.
/**
 * 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();
        }
    }
}