statementimpl.java

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/*  Sesame - Storage and Querying architecture for RDF and RDF Schema
 *  Copyright (C) 2001-2005 Aduna
 *
 *  Contact: 
 *  	Aduna
 *  	Prinses Julianaplein 14 b
 *  	3817 CS Amersfoort
 *  	The Netherlands
 *  	tel. [phone]
 *  	fax. [phone]
 *
 *  	http://aduna.biz/
 *  	http://www.openrdf.org/
 *  
 *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package org.openrdf.model.impl;

import java.io.Serializable;

import org.openrdf.model.Resource;
import org.openrdf.model.Statement;
import org.openrdf.model.URI;
import org.openrdf.model.Value;

/**
 * An implementation of the Statement interface.
 *
 * @author Arjohn Kampman
 * @version $Revision: 1.5 $
 **/
public class StatementImpl implements Statement, Serializable  {

/*---------------------------------------+
| Variables                              |
+---------------------------------------*/

	/**
	 * subject
	 **/
    private Resource _subject;

	/**
	 * predicate
	 **/
    private URI _predicate;

	/**
	 * object
	 **/
	private Value _object;

/*---------------------------------------+
| Constructors                           |
+---------------------------------------*/

	/**
	 * Creates a new Statement with the supplied subject, predicate and object.
	 *
	 * @param subject The statement's subject.
	 * @param predicate The statement's predicate.
	 * @param object The statement's object.
	 **/
	public StatementImpl(Resource subject, URI predicate, Value object) {
		_subject = subject;
		_predicate = predicate;
		_object = object;
	}

/*---------------------------------------+
| Methods                                |
+---------------------------------------*/

	// inherit comments
	public Resource getSubject() {
		return _subject;
	}

	// inherit comments
	public URI getPredicate() {
		return _predicate;
	}

	// inherit comments
	public Value getObject() {
		return _object;
	}

	/**
	 * Compares this statement to another object.
	 *
	 * @param other The Object to compare ths resource to.
	 * @return <tt>true</tt> if this statement is equal to the supplied
	 * object, <tt>false</tt> otherwise.
	 **/
    public boolean equals(Object other) {
		if (this == other) {
			return true;
		}

        if (other instanceof Statement) {
			Statement otherSt = (Statement)other;

			// The object is potentially the cheapest to check, as types
			// of these references might be different.

			// In general the number of different predicates in sets of
			// statements is the smallest, so predicate equality is checked
			// last.
			return
				_object.equals(otherSt.getObject()) &&
				_subject.equals(otherSt.getSubject()) &&
				_predicate.equals(otherSt.getPredicate());
        }

        return false;
    }

	/**
	 * Returns a hashcode for use in hash tables.
	 **/
	public int hashCode() {
		return
			(_subject.hashCode() & 0xFF0000) |
			(_predicate.hashCode() & 0x00FF00) |
			(_object.hashCode() & 0x0000FF);
	}

	/**
	 * Compares this Statement with the supplied object.
	 *
	 * @throws ClassCastException if o is not of type Statement
	 * @see java.lang.Comparable
	 **/
	public int compareTo(Object o) {
		if (this == o) {
			return 0;
		}

		Statement other = (Statement)o;

		int result = 0;

		result = _object.compareTo(other.getObject());

		if (result == 0) {
			// objects are equal
			result = _subject.compareTo(other.getSubject());
		}

		if (result == 0) {
			// subjects and objects are equal
			result = _predicate.compareTo(other.getPredicate());
		}

		return result;
	}

	/**
	 * Gives a String-representation of this Statement that can be used for
	 * debugging.
	 **/
	public String toString() {
		StringBuffer result = new StringBuffer(256);

		result.append("(");
		result.append(_subject.toString());
		result.append(", ");
		result.append(_predicate.toString());
		result.append(", ");
		result.append(_object.toString());
		result.append(")");

		return result.toString();
	}
}