fifoconflictresolver.java

rule engine drools-2.0-beta-18

package org.drools.conflict;

/*
 * $Id: FifoConflictResolver.java,v 1.3 2004/11/19 02:12:42 mproctor Exp $
 *
 * Copyright 2001-2003 (C) The Werken Company. All Rights Reserved.
 *
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided that the
 * following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright statements and
 * notices. Redistributions must also contain a copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. The name "drools" must not be used to endorse or promote products derived
 * from this Software without prior written permission of The Werken Company.
 * For written permission, please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "drools" nor may
 * "drools" appear in their names without prior written permission of The Werken
 * Company. "drools" is a trademark of The Werken Company.
 *
 * 5. Due credit should be given to The Werken Company. (http://werken.com/)
 *
 * THIS SOFTWARE IS PROVIDED BY THE WERKEN COMPANY AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE WERKEN COMPANY OR ITS CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

import org.drools.spi.Activation;
import org.drools.spi.ConflictResolver;

/**
 * <code>ConflictResolver</code> that orders rules on a First-In-First-Out
 * basis.
 * 
 * @see #getInstance
 * 
 * @author <a href="mailto:[e-mail]">Simon Harris </a>
 * 
 * @version $Id: RandomConflictResolver.java,v 1.1 2004/06/25 01:55:16 mproctor
 *          Exp $
 */
public class FifoConflictResolver extends AbstractConflictResolver
{
    // ----------------------------------------------------------------------
    // Class members
    // ----------------------------------------------------------------------

    /** Singleton instance. */
    private static final FifoConflictResolver INSTANCE = new FifoConflictResolver( );

    // ----------------------------------------------------------------------
    // Class methods
    // ----------------------------------------------------------------------

    /**
     * Retrieve the singleton instance.
     * 
     * @return The singleton instance.
     */
    public static ConflictResolver getInstance()
    {
        return INSTANCE;
    }

    // ----------------------------------------------------------------------
    // Constructors
    // ----------------------------------------------------------------------

    /**
     * Construct.
     */
    public FifoConflictResolver()
    {
        // intentionally left blank
    }

    // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    /**
     * @see ConflictResolver
     */
    public int compare(Activation lhs,
                       Activation rhs)
    {
        return (int) (lhs.getActivationNumber( ) - rhs.getActivationNumber( ));
    }
}