策略模式

最新推荐文章于 2023-10-19 21:21:14 发布

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本文介绍了一种基于策略模式的商场会员折扣系统实现方法。通过定义不同的折扣策略接口及其实现，实现了会员和非会员的不同折扣计算。利用枚举类简化了折扣类型的管理，并通过测试方法验证了系统的正确性。

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以商场会员打折为例

打折的订单

package study.strategy.myStrategy.entity;

import java.math.BigDecimal;

import study.strategy.myStrategy.DiscountType;

/**
 * 待结算的订单
 * @author an
 *
 */
public class Order {
	
	
	/**
	 * 待结算的金额
	 */
	private BigDecimal sum;
	
	/**
	 * 订单编码
	 */
	private String accountNo;

	public BigDecimal getSum() {
		return sum;
	}

	public void setSum(BigDecimal sum) {
		this.sum = sum;
	}

	public String getAccountNo() {
		return accountNo;
	}

	public void setAccountNo(String accountNo) {
		this.accountNo = accountNo;
	}
	/**
	 * 订单打折方法
	 * @param discountType
	 * @return
	 */
	public DiscountResult getDiscountResult(DiscountType discountType){
		return discountType.getDiscountedWay().discountAction(this);
	}
	
	
}

打折之后的结果

package study.strategy.myStrategy.entity;

import java.math.BigDecimal;

/**
 * 返回的打折结果
 * @author an
 *
 */
public class DiscountResult {
	
	/**
	 * 订单编号
	 */
	private String accountNo;
	
	/**
	 * 原价
	 */
	private BigDecimal sum;
	
	/**
	 * 打折之后的价格
	 */
	private BigDecimal accountSum;

	public String getAccountNo() {
		return accountNo;
	}

	public void setAccountNo(String accountNo) {
		this.accountNo = accountNo;
	}

	public BigDecimal getSum() {
		return sum;
	}

	public void setSum(BigDecimal sum) {
		this.sum = sum;
	}

	public BigDecimal getAccountSum() {
		return accountSum;
	}

	public void setAccountSum(BigDecimal accountSum) {
		this.accountSum = accountSum;
	}

	@Override
	public String toString() {
		return "原价是：" + sum + ", 折后价是：" + accountSum;
	}
	
	
	
}

打折的接口方法

package study.strategy.myStrategy;

import study.strategy.myStrategy.entity.DiscountResult;
import study.strategy.myStrategy.entity.Order;

/**
 * 打折方式
 * @author an
 *
 */
public interface DiscountedWay {
	
	DiscountResult discountAction(Order order);
	
}

会员的打折方式

package study.strategy.myStrategy;

import java.math.BigDecimal;

import study.strategy.myStrategy.entity.DiscountResult;
import study.strategy.myStrategy.entity.Order;
/**
 * 会员的打折方式
 * @author an
 *
 */
public class MemberDiscountWay implements DiscountedWay {
	
	private static final BigDecimal M_RATE = new BigDecimal(0.7);
	
	@Override
	public DiscountResult discountAction(Order order) {
		DiscountResult dis = new DiscountResult();
		dis.setAccountNo(order.getAccountNo());
		dis.setSum(order.getSum());
		dis.setAccountSum(order.getSum().multiply(M_RATE));
		return dis;
	}

}

非会员的打折方式

package study.strategy.myStrategy;

import java.math.BigDecimal;

import study.strategy.myStrategy.entity.DiscountResult;
import study.strategy.myStrategy.entity.Order;
/**
 * 非会员打折方式
 * @author an
 *
 */
public class UNMemberDiscountWay implements DiscountedWay {

	private static final BigDecimal UNM_RATE = new BigDecimal(0.8);
	
	@Override
	public DiscountResult discountAction(Order order) {
		DiscountResult dis = new DiscountResult();
		dis.setAccountNo(order.getAccountNo());
		dis.setSum(order.getSum());
		dis.setAccountSum(order.getSum().multiply(UNM_RATE));
		return dis;
	}

}

枚举类工具

package study.strategy.myStrategy;

public enum DiscountType {
	MEMBER(new MemberDiscountWay()),
	UNMEMBER(new UNMemberDiscountWay());
	
	private DiscountedWay discountedWay;
	DiscountType(DiscountedWay discountedWay){
		this.discountedWay = discountedWay;
	}
	
	public DiscountedWay getDiscountedWay(){
		return discountedWay;
	}
	
}

测试方法

package study.strategy.myStrategy;

import java.math.BigDecimal;

import study.strategy.myStrategy.entity.DiscountResult;
import study.strategy.myStrategy.entity.Order;

public class StrategyTest {
	public static void main(String[] args) {
		Order order = new Order();
		order.setAccountNo("NO000001");
		order.setSum(new BigDecimal(100));
		DiscountResult way =order.getDiscountResult(DiscountType.MEMBER);
		System.out.println(way);
		way =order.getDiscountResult(DiscountType.UNMEMBER);
		System.out.println(way);
	}
}

运行结果

原价是：100, 折后价是：69.9999999999999955591079014993738383054733276367187500
原价是：100, 折后价是：80.0000000000000044408920985006261616945266723632812500