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 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 }