discount.java

Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规则

/*
 * Copyright (C) 1999-2004 <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</a>
 *
 * 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 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.mandarax.examples.crm.domainmodel;


/**
 * Discount. A discount can be given in percent (relative
 * discount) or in $ (absolute discount).
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 1.2
 */
public class Discount extends BusinessObject {

    private double  rate     = 0;
    private boolean relative = true;
    
    /**
     * Constructor. The discount will be relative (a percentage).
     */
    public Discount() {
        super ();
    }

    /**
     * Constructor. The discount will be relative (a percentage)
     * @param d the discount
     */
    public Discount(double d) {
        super ();

        rate = d;
    }

    /**
     * Constructor. The discount will be relative (a percentage)
     * @param d the discount
     * @param rel - if true, the discount will be relative (a percentage),
     * if false, the discount will be absolute (an amount of US $)
     */
    public Discount(double d, boolean rel) {
        super ();

        rate     = d;
        relative = rel;
    }

    /**
     * Apply the discount to an amount.
     * @return the final amount (-discount)
     * @param amount an amount
     */
    public double apply(double amount) {
        if(relative) {
            return(100 - rate) * amount / 100;
        } else {
            return Math.max (0, amount - rate);
        }
    }

    /**
     * Get the rate.
     * @return the discount rate (either an absolute amount or a percentage value)
     */
    public double getRate() {
        return rate;
    }

    /**
     * Indicates whether the discount is relative.
     * @return true if the discount is a percentage, false otherwise (= if it is an absolute amount)
     */
    public boolean isRelative() {
        return relative;
    }

    /**
     * Set the rate.
     * @param r a value
     */
    public void setRate(double r) {
        rate = r;
    }

    /**
     * Set the relative property.
     * @param flag true if this should be a percentage value, false otherwise
     */
    public void setRelative(boolean flag) {
        relative = flag;
    }

    /**
     * Convert the object to a string.
     */
    public String toString() {
        return String.valueOf (rate) + (relative
                                        ? "%"
                                        : "$");
    }

	/**
	 * Compares objects.
	 * @return boolean
	 * @param obj java.lang.Object
	 */
	public boolean equals(Object obj) {
	    return obj!=null && (obj instanceof Discount) && ((Discount) obj).relative==relative && ((Discount) obj).rate==rate;
	}

	/**
	 * Get the hash code of the object.
	 * @return int
	 */
	public int hashCode() {
	    return (int)rate;
	}
}