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.db;

/**
 * Discount. A discount can be given in percent (relative
 * discount) or in $ (absolute discount). This class is a very simple business object type 
 * and shows how (arbitrary) objects are integrated. Being serializable is not required but recommended to support
 * technologies such as Serialization, RMI and EJB.
 * @since 2.2
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 */
public class Discount implements java.io.Serializable {
	private double rate  = 0;
	private boolean relative = true;
/**
 * Constructor.
 */
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 $)
 */
public Discount(double d,boolean rel) {
	super();
	rate = d;
	relative = rel;
}
/**
 * Apply the discount to an amount.
 * @return the final amount (-discount)
 * @param amount an amount
 */
public double apply(double amount) {
	if (relative) return (100-rate)*amount/100;
	else return Math.max(0,amount-rate);
}
/**
 * Get the rate.
 * @return the discount rate (either an absolute amount or a percentage value)
 */
public double getRate() {
	return rate;
}
/**
 * Indicates whether the discount is relative.
 * @return true if the discount is a percentage, false otherwise (= if it is an absolute amount)
 */
public boolean isRelative() {
	return relative;
}
/**
 * Set the rate.
 * @param r a value
 */
public void setRate(double r) {
	rate = r;
}
/**
 * Set the relative property.
 * @param flag true if this should be a percentage value, false otherwise
 */
public void setRelative(boolean flag) {
	relative = flag;
}
/**
 * Convert the object to a string.
 */
public String toString() {
	return String.valueOf(rate) + (relative?"%":"$");

}
}