/*

 * Copyright (c) 2014, 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 sun.misc;

/**

 * A utility class needed to access the root {@code ThreadGroup}

 *

 * The class should not depend on any others, because it' called from JNI_OnLoad of the AWT

 * native library. Triggering class loading could could lead to a deadlock.

 */

public final class ThreadGroupUtils {

    private ThreadGroupUtils() {

        // Avoid instantiation

    }

    /**

     * Returns a root thread group.

     * Should be called with {@link sun.security.util.SecurityConstants#MODIFY_THREADGROUP_PERMISSION}

     *

     * @return a root {@code ThreadGroup}

     */

    public static ThreadGroup getRootThreadGroup() {

        ThreadGroup currentTG = Thread.currentThread().getThreadGroup();

        ThreadGroup parentTG = currentTG.getParent();

        while (parentTG != null) {

            currentTG = parentTG;

            parentTG = currentTG.getParent();

        }

        return currentTG;

    }

}