ThreadUtils.java

/*
 * Distributed as part of mchange-commons-java 0.2.11
 *
 * Copyright (C) 2015 Machinery For Change, Inc.
 *
 * Author: Steve Waldman <swaldman@mchange.com>
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of EITHER:
 *
 *     1) The GNU Lesser General Public License (LGPL), version 2.1, as 
 *        published by the Free Software Foundation
 *
 * OR
 *
 *     2) The Eclipse Public License (EPL), version 1.0
 *
 * You may choose which license to accept if you wish to redistribute
 * or modify this work. You may offer derivatives of this work
 * under the license you have chosen, or you may provide the same
 * choice of license which you have been offered here.
 *
 * This software 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.
 *
 * You should have received copies of both LGPL v2.1 and EPL v1.0
 * along with this software; see the files LICENSE-EPL and LICENSE-LGPL.
 * If not, the text of these licenses are currently available at
 *
 * LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 *  EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php 
 * 
 */

package com.mchange.v2.lang;

import com.mchange.v2.log.*;
import java.lang.reflect.Method;

public final class ThreadUtils
{
    private final static MLogger logger = MLog.getLogger( ThreadUtils.class );

    final static Method holdsLock;

    static
    {
	Method _holdsLock;
	try
	    { _holdsLock = Thread.class.getMethod("holdsLock", new Class[] { Object.class }); }
	catch (NoSuchMethodException e)
	    { _holdsLock = null; }

	holdsLock = _holdsLock;
    }

    public static void enumerateAll( Thread[] threads )
    { ThreadGroupUtils.rootThreadGroup().enumerate( threads ); }

    /**
     * @return null if cannot be determined, otherwise true or false
     */
    public static Boolean reflectiveHoldsLock( Object o )
    {
	try
	    {
		if (holdsLock == null)
		    return null;
		else
		    return (Boolean) holdsLock.invoke( null, new Object[] { o } );
	    }
	catch (Exception e)
	    {
		if ( logger.isLoggable( MLevel.FINER ) )
		    logger.log( MLevel.FINER, "An Exception occurred while trying to call Thread.holdsLock( ... ) reflectively.", e);
		return null;
	    }
    }

    private ThreadUtils()
    {}
}