策略模式-商场促销-大话设计模式

类结构：

//父类，商场结账的算法
public interface SuperCash {
	//得到算过后的结账金额
	public double getcash(double cash);
}

//正常的结账
public class NormalCash implements SuperCash{

	public double getcash(double cash) {
		return cash;
	}

}

//对购买的货物进行打折的结账方式
public class DiscountCash implements SuperCash{
	private float moneyRebate;//打折的折扣
	public DiscountCash(float moneyRebate){
		this.moneyRebate=moneyRebate;
	}
	public double getcash(double cash) {
		return moneyRebate*cash;
	}

}

//买五百送三百的这种方式结账
public class ReturnCash implements SuperCash{
	private float upcash;//五百
	private float downcash;//三百
	public ReturnCash(float upcash,float downcash){
		this.upcash=upcash;
		this.downcash=downcash;
	}
	public double getcash(double cash) {
		double result=cash;
		if(cash>=upcash){
			result=cash-(Math.floor(cash/upcash)*downcash);
		}
		return result;
	}
}

//算法选择，并输出结果
public class CashContext {
	private SuperCash supercash;
	public CashContext(String type){
		//超市收款用多个算法类来进行使用和选择
		if("正常收费".equals(type)){
			
			supercash=new NormalCash();
		}else if(type.matches("打.+折")){
			
			float cash=Float.parseFloat(type.replaceAll("打(.+)折", "$1"));
			supercash=new DiscountCash(cash/10);
		}else if(type.matches("满.+送.+")){
			
			float cashup=Float.parseFloat(type.replaceAll("满(.+)送.+", "$1"));
			float cashdown=Float.parseFloat(type.replaceAll("满.+送(.+)", "$1"));
			supercash=new ReturnCash(cashup,cashdown);
		}
	}
	public double getResult(double cash){
		return supercash.getcash(cash);
	}
}

public class Test {
	//策略模式：策略封装了变化
	//也就是超市收款用多个算法类来进行使用和选择
	public static void main(String[] args) {
//		String type="正常收费";//输出:400.0
//		String type="打8折";//输出:320.0000047683716
		String type="满150送50";//输出:300.0
		CashContext context = new CashContext(type);
		double cash=context.getResult(400);
		System.out.println(cash);
	}
}