/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */
package java.io;

import java.util.*;
import java.io.File;
import jdk.internal.misc.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();
 }
 }
}