1 /*
   2  * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.internal.ref;
  27 
  28 import jdk.internal.misc.InnocuousThread;
  29 
  30 import java.lang.ref.Cleaner;
  31 import java.security.AccessController;
  32 import java.security.PrivilegedAction;
  33 import java.util.concurrent.ThreadFactory;
  34 
  35 /**
  36  * CleanerFactory provides a Cleaner for use within system modules.
  37  * The cleaner is created on the first reference to the CleanerFactory.
  38  */
  39 public final class CleanerFactory {
  40 
  41     /* The common Cleaner. */
  42     private final static Cleaner commonCleaner = Cleaner.create(new ThreadFactory() {
  43         @Override
  44         public Thread newThread(Runnable r) {
  45             return AccessController.doPrivileged(new PrivilegedAction<>() {
  46                 @Override
  47                 public Thread run() {
  48                     Thread t = InnocuousThread.newSystemThread("Common-Cleaner", r);
  49                     t.setPriority(Thread.MAX_PRIORITY - 2);
  50                     return t;
  51                 }
  52             });
  53         }
  54     });
  55 
  56     /**
  57      * Cleaner for use within system modules.
  58      *
  59      * This Cleaner will run on a thread whose context class loader
  60      * is {@code null}. The system cleaning action to perform in
  61      * this Cleaner should handle a {@code null} context class loader.
  62      *
  63      * @return a Cleaner for use within system modules
  64      */
  65     public static Cleaner cleaner() {
  66         return commonCleaner;
  67     }
  68 }