TripleIDComparatorSPO.java

/**
 * File: $HeadURL: https://hdt-java.googlecode.com/svn/trunk/hdt-java/src/org/rdfhdt/hdt/triples/TripleIDComparator.java $
 * Revision: $Rev: 191 $
 * Last modified: $Date: 2013-03-03 11:41:43 +0000 (dom, 03 mar 2013) $
 * Last modified by: $Author: mario.arias $
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Contacting the authors:
 *   Mario Arias:               mario.arias@deri.org
 *   Javier D. Fernandez:       jfergar@infor.uva.es
 *   Miguel A. Martinez-Prieto: migumar2@infor.uva.es
 *   Alejandro Andres:          fuzzy.alej@gmail.com
 */

package org.rdfhdt.hdt.triples;

import java.util.Comparator;


/**
 * Comparator between triples, based on the TripleComponentOrder
 * 
 */
public final class TripleIDComparatorSPO implements Comparator<TripleID> {

	// Singleton
	private static TripleIDComparatorSPO instance;
	public static TripleIDComparatorSPO getInstance() {
		if(instance==null) {
			instance = new TripleIDComparatorSPO();
		}
		return instance;
	}
	
	/*
	 * (non-Javadoc)
	 * 
	 * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
	 */
	@Override
	public int compare(TripleID o1, TripleID o2) {

		int result = o1.getSubject() - o2.getSubject();

		if (result == 0) {
			result = o1.getPredicate() - o2.getPredicate();
			if (result == 0) {
				// The third component is different?
				return o1.getObject() - o2.getObject();
			} else {
				// the second component is different
				return result;
			}
		} else {
			// the first component is different
			return result;
		}
	}

}