1 /*
   2  * Copyright (c) 2014, 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 sun.awt.util;
  27 
  28 /**
  29  * A utility class needed to access the root {@code ThreadGroup}
  30  *
  31  * The class should not depend on any others, because it' called from JNI_OnLoad of the AWT
  32  * native library. Triggering class loading could could lead to a deadlock.
  33  */
  34 public final class ThreadGroupUtils {
  35 
  36     private ThreadGroupUtils() {
  37         // Avoid instantiation
  38     }
  39 
  40     /**
  41      * Returns a root thread group.
  42      * Should be called with {@link sun.security.util.SecurityConstants#MODIFY_THREADGROUP_PERMISSION}
  43      *
  44      * @return a root {@code ThreadGroup}
  45      */
  46     public static ThreadGroup getRootThreadGroup() {
  47         ThreadGroup currentTG = Thread.currentThread().getThreadGroup();
  48         ThreadGroup parentTG = currentTG.getParent();
  49         while (parentTG != null) {
  50             currentTG = parentTG;
  51             parentTG = currentTG.getParent();
  52         }
  53         return currentTG;
  54     }
  55 }