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

约定不等于承诺〃 2022-03-20 11:54 123阅读 0赞

### 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;
    	}
    	@Override
    	public 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 ######

@Test
    	public 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));
    		
    	}