src/java.base/share/classes/java/io/DeleteOnExitHook.java

/*
 * Copyright (c) 2005, 2023, 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
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package java.io;

import java.util.*;

import jdk.internal.access.SharedSecrets;

/**
 * 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 LinkedHashSet<String> files = new LinkedHashSet<>();
    static {
        // DeleteOnExitHook must be the last shutdown hook to be invoked.
        // Application shutdown hooks may add the first file to the
        // delete-on-exit list and cause the DeleteOnExitHook to be
        // registered during shutdown in progress. So set the
        // registerShutdownInProgress parameter to true.
        SharedSecrets.getJavaLangAccess()
            .registerShutdownHook(2 /* Shutdown hook invocation order */,
                true /* register even if shutdown in progress */,
                new Runnable() {
                    public void run() {
                       runHooks();
                    }
                }
        );
    }

    private DeleteOnExitHook() {}

    static synchronized void add(String file) {
        if(files == null) {
            // DeleteOnExitHook is running. Too late to add a file
            throw new IllegalStateException("Shutdown in progress");
        }

        files.add(file);
    }

    static void runHooks() {
        LinkedHashSet<String> theFiles;

        synchronized (DeleteOnExitHook.class) {
            theFiles = files;
            files = null;
        }

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