分期利息计算——考虑免息日期和多利率设定的思路设计和代码实现

利息计算——考虑免息日期和多利率设定的思路设计和代码实现"/>

分期利息计算——考虑免息日期和多利率设定的思路设计和代码实现

文章目录

• • • • • 前言
        • 需求描述
        • 思路描述
        • 代码实现
        • • 利率规则实体
          • 工具方法-计算第 j 阶段前(0到j-1)阶段一共几天
          • 测试方法

前言

利息计算是一种常见的需求，尤其在现在这种分期还款场景比较常见的情况下。

需求描述

用户可以分期归还利息
多期，每一期利率不同，天数不同
利息计算以本金为基准，不设置利滚利
可以设置免息日，免息日内不计算利息
第一期和免息日起始时间是同一天
对于超于最后一个利率规则的天数按照最后一个利率规则计算利息

思路描述

1、为分期利率设置数据结构，比如第几期，利率，计息天数
2、使用循环遍历的方式判断
2.1、每一期内的计息天数
2.2、每一期内的免息天数
2.3、如果是最后一期，则需要考虑多余的天数也按照这个利率进行计算

代码实现

利率规则实体

import org.apache.commons.lang.builder.ToStringBuilder;
/*** 分期利率信息实体* @author jie.wu*/
public class Rates{private int index;//第几阶段利率private int days;//本利率执行天数 比如 第1-10天，1%;第11-20天，2%;第21-30天，3%private String rates;//利率值public Rates(){}public Rates(int index,int days,String rates){this.index=index;this.days=days;this.rates=rates;}public int getIndex() {return index;}public void setIndex(int index) {this.index = index;}public int getDays() {return days;}public void setDays(int days) {this.days = days;}public String getRates() {return rates;}public void setRates(String rates) {this.rates = rates;}@Overridepublic String toString() {return ToStringBuilder.reflectionToString(this);}
}

工具方法-计算第 j 阶段前(0到j-1)阶段一共几天

比如第一阶段10天，第二阶段10天，则第三阶段这个方法返回20

/*** 计算本阶段之前一共有几天* @param j* @param ratesArray* @return*/private static int getForeDays(int j,Rates[] ratesArray){int foreDays=0;for(int i=0;i<j;i++){foreDays+=ratesArray[i].getDays();}return foreDays;}

• 计算第 j 阶段需要计算的利息天数

需要考虑免息日的情况

/*** 计算第 j 阶段需要计算利息的天数* 对于垫资天数超过所有设定阶段天数总和的，多余的天数按照最后一个利率进行计算* @param j   第几阶段-从0计数* @param freeDays   免息日* @param fullDays   总垫资日* @param ratesArray 利率设定数组* @return */private static BigDecimal getTemDays(int j,int freeDays,int fullDays,Rates[] ratesArray){//如果是第一阶段if(j==0){//本阶段减去免息日//如果为正值则取该值//如果为负值，则本阶段不计算利息return new BigDecimal(ratesArray[j].getDays()-freeDays>0?ratesArray[j].getDays()-freeDays:0);}//如果是最后一个阶段if(j==ratesArray.length-1){//计算之前几个阶段的天数和-不包括本阶段int foreDays=getForeDays(j,ratesArray);//计算本阶段以及之后阶段免息日天数int temfreeDays=freeDays-foreDays>0?freeDays-foreDays:0;//计算本阶段垫资的天数int temDays=fullDays-foreDays>0?fullDays-foreDays:0;//将本阶段之后的天数也作为本阶段来考虑//将本阶段免息日期考虑进来temDays=temDays-temfreeDays>0?temDays-temfreeDays:0;return new BigDecimal(temDays);}else{//计算之前几个阶段的天数和-不包括本阶段int foreDays=getForeDays(j,ratesArray);//计算本阶段以及之后阶段免息日天数int temfreeDays=freeDays-foreDays>0?freeDays-foreDays:0;//计算本阶段垫资的天数int temDays=fullDays-foreDays>0?fullDays-foreDays:0;//考虑总垫资天数超过本阶段的情况,则本阶段仅取本阶段的天数if(temDays>ratesArray[j].getDays()){temDays=ratesArray[j].getDays();}//将本阶段免息日期考虑进来temDays=temDays-temfreeDays>0?temDays-temfreeDays:0;return new BigDecimal(temDays);}}

测试方法

@Testpublic void testMethod(){long beginDate=new Date().getTime();//今天距离垫资日天数int fullDays=987;//免息日为 3 天int freeDays=2;//本金BigDecimal principal=new BigDecimal("100");//分期利率规则 json 字符串String arrayStr="[{\"days\":10,\"index\":1,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":2,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":3,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":4,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":5,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":6,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":7,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":8,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":9,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":10,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":11,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":12,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":13,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":14,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":15,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":16,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":17,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":18,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":19,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":20,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":21,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":22,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":23,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":24,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":25,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":26,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":27,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":28,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":29,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":30,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":31,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":32,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":33,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":34,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":35,\"rates\":\"0.01\"},"+ "{\"days\":10,\"index\":36,\"rates\":\"0.01\"}]";//将字符串转化为 JSONArray 对象JSONArray array=JSONArray.fromObject(arrayStr);//数组长度int size=array.size();Rates[] ratesArray=new Rates[size];//按照排序将利率存放到数组for(int i=0;i<array.size();i++){Rates rates=(Rates)JSONObject.toBean((JSONObject) array.get(i),Rates.class);ratesArray[rates.getIndex()-1]=rates;}//程序运行到这里，利率已经按照先后顺序排列好了//利息总金额BigDecimal sumInterest=new BigDecimal("0");for(int j=0;j<ratesArray.length;j++){//都只计算本阶段都利率//现在是第 j 阶段System.out.print("现在是第"+j+"阶段;");//计算借款天数在本阶段借款天数-需要考虑免息日第情况//如果是最后一个利率阶段，垫资天数还在延续，则将多余天数计算到最后一个利率中BigDecimal temDays=getTemDays(j,freeDays,fullDays,ratesArray);//本阶段的利息BigDecimal temInterest=new BigDecimal("0");temInterest=new BigDecimal(ratesArray[j].getRates()).multiply(temDays).multiply(principal);System.out.println("本阶段的利息为:"+temInterest);sumInterest=sumInterest.add(temInterest);}long endDate=new Date().getTime();System.out.println("最后利息总额："+sumInterest+";耗时："+(endDate-beginDate));}