银行等额本息还款算法

等额本息算法公式

每月还款额=[贷款本金×月利率×（1+月利率）^还款月数]÷[（1+月利率）^还款月数－1]

/**
 * 说明:等额本息还款算法
 * 
 * @author ljf <[e-mail]>
 * @date 2017-2-6 下午4:28:55
 * @version V1.2
 */
public class PrincipalAndInterestEquals {

   /**
    * @param args
    */
   public static void main(String[] args) {
       BigDecimal invest = new BigDecimal(139000); // 本金
       double yearRate = 0.059; // 年利率
       int year = 15;//期限
       double monthRate = yearRate / 12;
       int month = year * 12;
       // 每月本息金额  = (本金×月利率×(1＋月利率)＾还款月数)÷ ((1＋月利率)＾还款月数-1)
       BigDecimal monthIncome = invest.multiply(new BigDecimal(monthRate * Math.pow(1 +
               monthRate, month))).divide(new BigDecimal(Math.pow(1 + monthRate, month) - 1), 2,
               BigDecimal.ROUND_HALF_UP);
       System.out.println("每月本息金额 : " + monthIncome);
       System.out.println("---------------------------------------------------");
       // 每月本金 = 本金×月利率×(1+月利率)^(还款月序号-1)÷((1+月利率)^还款月数-1)
       BigDecimal monthCapital;
       BigDecimal sumCapital = BigDecimal.ZERO;
       for (int i = 1; i < month + 1; i++) {
           monthCapital = invest.multiply(new BigDecimal(monthRate * (Math.pow((1 + monthRate),
                   i - 1)))).divide(new BigDecimal(Math.pow(1 + monthRate, month) - 1), 2,
                   BigDecimal.ROUND_HALF_UP);
           System.out.println("第" + i + "月本金： " + monthCapital);
           sumCapital = sumCapital.add(monthCapital);
       }
       System.out.println("---------------------------------------------------");
       // 每月利息  = 剩余本金 x 贷款月利率
       BigDecimal monthInterest;
       BigDecimal capital = invest;
       BigDecimal tmpCapital = BigDecimal.ZERO;
       BigDecimal sumInterest = BigDecimal.ZERO;
       for (int i = 1; i < month + 1; i++) {
           capital = capital.subtract(tmpCapital);
           monthInterest = capital.multiply(new BigDecimal(monthRate)).setScale(2, BigDecimal
                   .ROUND_HALF_UP);
           tmpCapital = invest.multiply(new BigDecimal(monthRate * (Math.pow((1 + monthRate), i
                   - 1)))).divide(new BigDecimal(Math.pow(1 + monthRate, month) - 1), 2,
                   BigDecimal.ROUND_HALF_UP);
           System.out.println("第" + i + "月利息： " + monthInterest);

           sumInterest = sumInterest.add(monthInterest);
       }
       System.out.println("本金总和：" + sumCapital + " 利息总和：" + sumInterest);
   }
}