001    //$HeadURL: svn+ssh://jwilden@svn.wald.intevation.org/deegree/base/branches/2.5_testing/src/org/deegree/framework/util/IDGenerator.java $
002    /*----------------------------------------------------------------------------
003     This file is part of deegree, http://deegree.org/
004     Copyright (C) 2001-2009 by:
005       Department of Geography, University of Bonn
006     and
007       lat/lon GmbH
008    
009     This library is free software; you can redistribute it and/or modify it under
010     the terms of the GNU Lesser General Public License as published by the Free
011     Software Foundation; either version 2.1 of the License, or (at your option)
012     any later version.
013     This library is distributed in the hope that it will be useful, but WITHOUT
014     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
015     FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
016     details.
017     You should have received a copy of the GNU Lesser General Public License
018     along with this library; if not, write to the Free Software Foundation, Inc.,
019     59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
020    
021     Contact information:
022    
023     lat/lon GmbH
024     Aennchenstr. 19, 53177 Bonn
025     Germany
026     http://lat-lon.de/
027    
028     Department of Geography, University of Bonn
029     Prof. Dr. Klaus Greve
030     Postfach 1147, 53001 Bonn
031     Germany
032     http://www.geographie.uni-bonn.de/deegree/
033    
034     e-mail: info@deegree.org
035    ----------------------------------------------------------------------------*/
036    
037    package org.deegree.framework.util;
038    
039    /**
040     * Produces unique IDs (used to generate Request-IDs, for example).
041     * <p>
042     *
043     * @author <a href="mailto:mschneider@lat-lon.de">Markus Schneider</a>
044     * @version $Revision: 18195 $ $Date: 2009-06-18 17:55:39 +0200 (Do, 18 Jun 2009) $
045     */
046    public class IDGenerator {
047    
048        /**
049         * The only instance of this class.
050         */
051        private static IDGenerator instance = null;
052    
053        /** The current ID. */
054        private long id = 0;
055    
056        /**
057         * Returns the only instance of this class.
058         *
059         * @return the only instance of IDGenerator
060         *
061         */
062        synchronized public static IDGenerator getInstance() {
063            if ( instance == null )
064                instance = new IDGenerator();
065            return instance;
066        }
067    
068        /**
069         * Generates a completly unique ID.
070         *
071         * @return a unique ID
072         */
073        synchronized public long generateUniqueID() {
074            return id++;
075        }
076    }