TripleIDComparator.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.io.IOException;
import java.io.Serializable;
import java.util.Comparator;

import org.rdfhdt.hdt.enums.TripleComponentOrder;


/**
 * Comparator between triples, based on the TripleComponentOrder
 * 
 */
public class TripleIDComparator implements Comparator<TripleID>, Serializable {
	private static final long serialVersionUID = -8322949509663015732L;
	
	/** Determines the order of comparison */
	private TripleComponentOrder order;
	
	public static Comparator<TripleID> getComparator(TripleComponentOrder order) {
		if(order==TripleComponentOrder.SPO) {
			return TripleIDComparatorSPO.getInstance();
		}
		return new TripleIDComparator(order);
	}

	/**
	 * Basic constructor
	 * 
	 * @param order
	 *            The order to compare with
	 */
	private TripleIDComparator(TripleComponentOrder order) {
		super();
		this.order = order;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
	 */
	@Override
	public int compare(TripleID o1, TripleID o2) {
		/*
		 * Returns a negative integer, zero, or a positive integer as the first
		 * argument is less than, equal to, or greater than the second.
		 */
		/*
		 * Components of the triple. Meaning will be given based on the order
		 * variable, see below
		 */
		int x1 = 0, y1 = 0, z1 = 0, x2 = 0, y2 = 0, z2 = 0;

		switch (this.order) {
		case SPO:
			// Subjects
			x1 = o1.getSubject();
			x2 = o2.getSubject();
			// Predicates
			y1 = o1.getPredicate();
			y2 = o2.getPredicate();
			// Objects
			z1 = o1.getObject();
			z2 = o2.getObject();
			break;
		case SOP:
			// Subjects
			x1 = o1.getSubject();
			x2 = o2.getSubject();
			// Objects
			y1 = o1.getObject();
			y2 = o2.getObject();
			// Predicates
			z1 = o1.getPredicate();
			z2 = o2.getPredicate();
			break;
		case PSO:
			// Predicates
			x1 = o1.getPredicate();
			x2 = o2.getPredicate();
			// Subjects
			y1 = o1.getSubject();
			y2 = o2.getSubject();
			// Objects
			z1 = o1.getObject();
			z2 = o2.getObject();
			break;
		case POS:
			// Predicates
			x1 = o1.getPredicate();
			x2 = o2.getPredicate();
			// Objects
			y1 = o1.getObject();
			y2 = o2.getObject();
			// Subjects
			z1 = o1.getSubject();
			z2 = o2.getSubject();
			break;
		case OSP:
			// Objects
			x1 = o1.getObject();
			x2 = o2.getObject();
			// Subjects
			y1 = o1.getSubject();
			y2 = o2.getSubject();
			// Predicates
			z1 = o1.getPredicate();
			z2 = o2.getPredicate();
			break;
		case OPS:
			// Objects
			x1 = o1.getObject();
			x2 = o2.getObject();
			// Predicates
			y1 = o1.getPredicate();
			y2 = o2.getPredicate();
			// Subjects
			z1 = o1.getSubject();
			z2 = o2.getSubject();
			break;
		}

		int result = x1 - x2;

		if (result == 0) {
			result = y1 - y2;
			if (result == 0) {
				// The third component is different?
				return z1 - z2;
			} else {
				// the second component is different
				return result;
			}
		} else {
			// the first component is different
			return result;
		}
	}
	
	/** method for serialization of an instance of this class as specified by Serializable */
	private void writeObject(java.io.ObjectOutputStream out) throws IOException {
		out.defaultWriteObject();
	}
	/** method for deserialization of an instance of this class as specified by Serializable */
	private void readObject(java.io.ObjectInputStream in) 
			throws IOException, ClassNotFoundException {
		in.defaultReadObject();
	}
}