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商场促销打折场景下，使用策略模式实现计算最终支付金额

收费基类：

package com.zawl.designpattern.strategy;import java.math.BigDecimal;/** * @Description 收费基类 * @Author xiayunan 
   
     * @Version V1.0.0 * @Since 1.0 * @Date 2019/11/16 7:05 */public interface CashSuper {    public BigDecimal acceptCash(BigDecimal money);}
   

正常收费类继承收费基类：

package com.zawl.designpattern.strategy;import java.math.BigDecimal;/** * @Description 正常收费类 * @Author xiayunan 
   
     * @Version V1.0.0 * @Since 1.0 * @Date 2019/11/16 7:06 */public class CashNormal implements CashSuper {    @Override    public BigDecimal acceptCash(BigDecimal money) {        return money;    }}
   

折扣收费类实现收费基类

package com.zawl.designpattern.strategy;import java.math.BigDecimal;/** * @Description 打折收费类 * @Author xiayunan 
   
     * @Version V1.0.0 * @Since 1.0 * @Date 2019/11/16 7:07 */public class CashDiscount implements CashSuper {    private BigDecimal discountRate = new BigDecimal(1);    /**     * 折扣率，如打八折，就输入0.8     * @param discountRate     */    public  CashDiscount(BigDecimal discountRate){        this.discountRate = discountRate;    }    @Override    public BigDecimal acceptCash(BigDecimal money) {        return money.multiply(discountRate).setScale(2,BigDecimal.ROUND_HALF_UP);    }}
   

返现收费类实现收费基类：

package com.zawl.designpattern.strategy;import java.math.BigDecimal;/** * @Description 返现收费类 * @Author xiayunan 
   
     * @Version V1.0.0 * @Since 1.0 * @Date 2019/11/16 7:08 */public class CashReturn implements  CashSuper{    private BigDecimal moneyCondition  = BigDecimal.ZERO;    private BigDecimal moneyReturn = BigDecimal.ZERO;    /**     * 返利条件，如满300返100则moneyCondition为300，moneyReturn为100     * @param moneyCondition     * @param moneyReturn     */    public CashReturn(double moneyCondition, double moneyReturn) {        this.moneyCondition = new BigDecimal(moneyCondition);        this.moneyReturn = new BigDecimal(moneyReturn);    }    @Override    public BigDecimal acceptCash(BigDecimal money) {        //如果消费金额大于返利条件，        if(money.compareTo(moneyCondition)>=0){            money = money.subtract(moneyReturn);        }        return money;    }}
   

收费上下文对象：

package com.zawl.designpattern.strategy;import java.math.BigDecimal;/** * @Description 收费上下文对象 -- 策略模式 * @Author xiayunan 
   
     * @Version V1.0.0 * @Since 1.0 * @Date 2019/11/16 7:29 */public class CashContext {    private CashSuper cashSuper;    /**     * 简单工厂模式创建对象     * @param type     */    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));    }    public 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;        }        public  String key;        public  String value;        public String getKey() {            return key;        }        public void setKey(String key) {            this.key = key;        }        public String getValue() {            return value;        }        public void setValue(String value) {            this.value = value;        }    }}
   

收费类型常量类;

package com.zawl.designpattern.strategy;/** * @Description 收费类型常量类 * @Author xiayunan 
   
     * @Version V1.0.0 * @Since 1.0 * @Date 2019/11/16 7:57 */public class CashConstants {    /**正常收费*/    public  static final String NORMAL = "NORMAL";    /**打折收费*/    public  static final String DISCOUNT = "DISCOUNT";    /**返现收费*/    public  static final String RETURN = "RETURN";}
   

客户端调用：

package com.zawl.designpattern.strategy;import java.math.BigDecimal;/** * @Description 客户端 * @Author xiayunan 
   
     * @Version V1.0.0 * @Since 1.0 * @Date 2019/11/16 7:09 */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());    }}
   

运行结果：

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