折扣计算策略--设计模式应用
折扣计算，策略模式和装饰模式的具体应用。
package org.tang.zjnumall.strategy.discount;
import java.math.BigDecimal;
public abstract class AbstractDiscountStrategy {
/**
* 单价
*/
protected BigDecimal price;
/**
* 数量
*/
protected int copies;
protected AbstractDiscountStrategy() {
}
/**
* @param price 单价
* @param copies 数量
*/
public AbstractDiscountStrategy(BigDecimal price, int copies) {
this.price = price;
this.copies = copies;
}
/**
* 计算折扣额度
*
* @return
*/
public abstract BigDecimal calculateDiscount();
}
package org.tang.zjnumall.strategy.discount;
import java.math.BigDecimal;
/**
* 零折扣策略
* @author Tang
*
*/
public class NoDiscountStrategy extends AbstractDiscountStrategy {
@Override
public BigDecimal calculateDiscount() {
return new BigDecimal(0);
}
}
package org.tang.zjnumall.strategy.discount;
import java.math.BigDecimal;
/**
* 单位固定折扣额策略
* @author Tang
*
*/
public class FlatRateDiscountStrategy extends AbstractDiscountStrategy {
/**
* 单位折扣额
*/
private BigDecimal discount;
/**
*
* @param price 单价
* @param copies 数量
* @param discount 单位折扣额
*/
public FlatRateDiscountStrategy(int copies, BigDecimal discount) {
super.copies = copies;
this.discount = discount;
}
@Override
/**
* 总折扣额 = 数量 * 单位折扣额
*/
public BigDecimal calculateDiscount() {
return new BigDecimal(copies).multiply(this.discount);
}
}
package org.tang.zjnumall.strategy.discount;
import java.math.BigDecimal;
/**
* 折扣率策略
* @author Tang
*
*/
public class PercentageDiscountStrategy extends AbstractDiscountStrategy {
/**
* 单位折扣率
*/
private BigDecimal percent;
/**
*
* @param price 单价
* @param copies 数量
* @param percent 单位折扣率
*/
public PercentageDiscountStrategy(BigDecimal price, int copies, BigDecimal percent) {
super(price, copies);
this.percent = percent;
}
@Override
/**
* 总折扣额 = 单价 * 数量 * 单位折扣率
*
*/
public BigDecimal calculateDiscount() {
return price.multiply(new BigDecimal(copies)).multiply(this.percent);
}
}
package org.tang.zjnumall.strategy.discount;
import java.math.BigDecimal;
/**
* 限制折扣额策略
* @author Tang
*
*/
public class RestrictedDiscountStrategy extends AbstractDiscountStrategy {
/**
* 折扣额度上限
*/
private BigDecimal limit;
private AbstractDiscountStrategy strategy;
/**
*
* @param strategy 宿主策略
* @param limit 折扣限制额度
*/
public RestrictedDiscountStrategy(AbstractDiscountStrategy strategy, BigDecimal limit) {
this.limit = limit;
this.strategy = strategy;
}
@Override
/**
* 当折扣额超过折扣限制额度时，总折扣额变为限制折扣额
*/
public BigDecimal calculateDiscount() {
BigDecimal preDiscount = this.strategy.calculateDiscount();
if (this.limit.doubleValue() > 0 && preDiscount.compareTo(this.limit) > 0) {
return this.limit;
}
return preDiscount;
}
}
package org.tang.zjnumall.strategy.discount;
import java.math.BigDecimal;
public class DiscountCalculator {
/**
* 折扣策略
*/
private AbstractDiscountStrategy strategy;
public DiscountCalculator(){}
/**
*
* @param strategy 具体折扣策略
*/
public DiscountCalculator(AbstractDiscountStrategy strategy){
this.strategy = strategy;
}
public AbstractDiscountStrategy getStrategy() {
return strategy;
}
public void setStrategy(AbstractDiscountStrategy strategy) {
this.strategy = strategy;
}
public BigDecimal calculate(){
return null;
}
public static void main(String[] args){
BigDecimal price = new BigDecimal("99.99");
int copies = 9;
BigDecimal percent = new BigDecimal("0.12");
BigDecimal discount = new BigDecimal("10");
BigDecimal limit = new BigDecimal("100");
AbstractDiscountStrategy noDiscount = new NoDiscountStrategy();
AbstractDiscountStrategy percentStrategy = new PercentageDiscountStrategy(price, copies, percent);
AbstractDiscountStrategy flatRateStrategy = new FlatRateDiscountStrategy(copies, discount);
AbstractDiscountStrategy restrictedStrategy = new RestrictedDiscountStrategy(percentStrategy, limit);
System.out.println("折扣前总额："+price.multiply(new BigDecimal(copies)));
System.out.println("零折扣策略总折扣额："+noDiscount.calculateDiscount());
System.out.println("折扣率策略总折扣额："+percentStrategy.calculateDiscount());
System.out.println("固定折扣额策略总折扣额："+flatRateStrategy.calculateDiscount());
System.out.println("限制折扣额策略总折扣额："+restrictedStrategy.calculateDiscount());
}
}