策略模式在商场促销中的应用

在商场促销场景下，使用策略模式可以有效地实现计算最终支付金额的功能。本文将详细介绍相关实现。

收费基类

package com.zawl.designpattern.strategy;public interface CashSuper {    BigDecimal acceptCash(BigDecimal money);}

该接口定义了一个通用收费处理方法，用于计算最终支付金额。

正常收费类

package com.zawl.designpattern.strategy;public class CashNormal implements CashSuper {    @Override    public BigDecimal acceptCash(BigDecimal money) {        return money;    }}

实现了接口中的acceptCash方法，直接返回输入金额，不做任何调整。

折扣收费类

package com.zawl.designpattern.strategy;public class CashDiscount implements CashSuper {    private BigDecimal discountRate = new BigDecimal(1);    public CashDiscount(BigDecimal discountRate) {        this.discountRate = discountRate;    }    @Override    public BigDecimal acceptCash(BigDecimal money) {        return money.multiply(discountRate).setScale(2, BigDecimal.ROUND_HALF_UP);    }}

支持打折收费，根据输入的折扣率计算最终金额。

返现收费类

package com.zawl.designpattern.strategy;public class CashReturn implements CashSuper {    private BigDecimal moneyCondition = BigDecimal.ZERO;    private BigDecimal moneyReturn = BigDecimal.ZERO;    public CashReturn(double moneyCondition, double moneyReturn) {        this.moneyCondition = new BigDecimal(moneyCondition);        this.moneyReturn = new BigDecimal(moneyReturn);    }    @Override    public BigDecimal acceptCash(BigDecimal money) {        if (money.compareTo(moneyCondition) >= 0) {            money = money.subtract(moneyReturn);        }        return money;    }}

支持返现收费，根据消费金额和满足返现条件计算最终金额。

收费上下文对象

package com.zawl.designpattern.strategy;public class CashContext {    private CashSuper cashSuper;    public CashContext(String type) {        switch (type) {            case CashConstants.NORMAL:                cashSuper = new CashNormal();                break;            case CashConstants.DISCOUNT:                cashSuper = new CashDiscount(new BigDecimal(0.8));                break;            case CashConstants.RETURN:                cashSuper = new CashReturn(300, 100);                break;        }    }    public BigDecimal getResult(double money) {        return cashSuper.acceptCash(new BigDecimal(money));    }    enum CashEnum {        NORMAL("正常收费", "1"),        DISCOUNT("打折收费", "2"),        RETURN("返现收费", "3");        CashEnum(String key, String value) {            this.key = key;            this.value = value;        }        private String key;        private String value;        public String getKey() {            return key;        }        public String getValue() {            return value;        }    }}

该类用于根据不同的收费策略选择合适的处理逻辑，提供计算最终支付金额的功能。

收费类型常量类

package com.zawl.designpattern.strategy;public class CashConstants {    public static final String NORMAL = "NORMAL";    public static final String DISCOUNT = "DISCOUNT";    public static final String RETURN = "RETURN";}

定义了常用的收费类型标识符，供上下文对象使用。

客户端调用

package com.zawl.designpattern.strategy;public class Client {    public static void main(String[] args) {        CashContext context = new CashContext(CashConstants.RETURN);        BigDecimal result = context.getResult(300);        System.out.println("最终收费：" + result.toString());        context = new CashContext(CashConstants.NORMAL);        result = context.getResult(300);        System.out.println("最终收费：" + result.toString());        context = new CashContext(CashConstants.DISCOUNT);        result = context.getResult(300);        System.out.println("最终收费：" + result.toString());    }}

客户端代码用于创建不同的收费策略上下文，调用计算最终支付金额的方法。