等额本息：

/*** Description:等额本息工具类* Copyright: Copyright (corporation)2015* Company: Corporation* @author: 凯文加内特* @version: 1.0* Created at: 2015年11月30日 下午3:45:46* Modification History:* Modified by : */package com.utils;import java.math.BigDecimal;
import java.util.HashMap;
import java.util.Map;/*** 等额本息还款，也称定期付息，即借款人每月按相等的金额偿还贷款本息，其中每月贷款利息按月初剩余贷款本金计算并逐月结清。把按揭贷款的本金总额与利息总额相加，* 然后平均分摊到还款期限的每个月中。作为还款人，每个月还给银行固定金额，但每月还款额中的本金比重逐月递增、利息比重逐月递减。*/public class AverageCapitalPlusInterestUtils {/*** 等额本息计算获取还款方式为等额本息的每月偿还本金和利息* * 公式：每月偿还本息=〔贷款本金×月利率×(1＋月利率)＾还款月数〕÷〔(1＋月利率)＾还款月数-1〕* * @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 每月偿还本金和利息,不四舍五入，直接截取小数点最后两位*/public static double getPerMonthPrincipalInterest(double invest, double yearRate, int totalmonth) {double monthRate = yearRate / 12;BigDecimal monthIncome = new BigDecimal(invest).multiply(new BigDecimal(monthRate * Math.pow(1 + monthRate, totalmonth))).divide(new BigDecimal(Math.pow(1 + monthRate, totalmonth) - 1), 2, BigDecimal.ROUND_DOWN);return monthIncome.doubleValue();}/*** 等额本息计算获取还款方式为等额本息的每月偿还利息* * 公式：每月偿还利息=贷款本金×月利率×〔(1+月利率)^还款月数-(1+月利率)^(还款月序号-1)〕÷〔(1+月利率)^还款月数-1〕* @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 每月偿还利息*/public static Map<Integer, BigDecimal> getPerMonthInterest(double invest, double yearRate, int totalmonth) {Map<Integer, BigDecimal> map = new HashMap<Integer, BigDecimal>();double monthRate = yearRate/12;BigDecimal monthInterest;for (int i = 1; i < totalmonth + 1; i++) {BigDecimal multiply = new BigDecimal(invest).multiply(new BigDecimal(monthRate));BigDecimal sub  = new BigDecimal(Math.pow(1 + monthRate, totalmonth)).subtract(new BigDecimal(Math.pow(1 + monthRate, i-1)));monthInterest = multiply.multiply(sub).divide(new BigDecimal(Math.pow(1 + monthRate, totalmonth) - 1), 6, BigDecimal.ROUND_DOWN);monthInterest = monthInterest.setScale(2, BigDecimal.ROUND_DOWN);map.put(i, monthInterest);}return map;}/*** 等额本息计算获取还款方式为等额本息的每月偿还本金* * @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 每月偿还本金*/public static Map<Integer, BigDecimal> getPerMonthPrincipal(double invest, double yearRate, int totalmonth) {double monthRate = yearRate / 12;BigDecimal monthIncome = new BigDecimal(invest).multiply(new BigDecimal(monthRate * Math.pow(1 + monthRate, totalmonth))).divide(new BigDecimal(Math.pow(1 + monthRate, totalmonth) - 1), 2, BigDecimal.ROUND_DOWN);Map<Integer, BigDecimal> mapInterest = getPerMonthInterest(invest, yearRate, totalmonth);Map<Integer, BigDecimal> mapPrincipal = new HashMap<Integer, BigDecimal>();for (Map.Entry<Integer, BigDecimal> entry : mapInterest.entrySet()) {mapPrincipal.put(entry.getKey(), monthIncome.subtract(entry.getValue()));}return mapPrincipal;}/*** 等额本息计算获取还款方式为等额本息的总利息* * @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 总利息*/public static double getInterestCount(double invest, double yearRate, int totalmonth) {BigDecimal count = new BigDecimal(0);Map<Integer, BigDecimal> mapInterest = getPerMonthInterest(invest, yearRate, totalmonth);for (Map.Entry<Integer, BigDecimal> entry : mapInterest.entrySet()) {count = count.add(entry.getValue());}return count.doubleValue();}/*** 应还本金总和* @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 应还本金总和*/public static double getPrincipalInterestCount(double invest, double yearRate, int totalmonth) {double monthRate = yearRate / 12;BigDecimal perMonthInterest = new BigDecimal(invest).multiply(new BigDecimal(monthRate * Math.pow(1 + monthRate, totalmonth))).divide(new BigDecimal(Math.pow(1 + monthRate, totalmonth) - 1), 2, BigDecimal.ROUND_DOWN);BigDecimal count = perMonthInterest.multiply(new BigDecimal(totalmonth));count = count.setScale(2, BigDecimal.ROUND_DOWN);return count.doubleValue();}/*** @param args*/public static void main(String[] args) {double invest = 20000; // 本金int month = 12;double yearRate = 0.15; // 年利率double perMonthPrincipalInterest = getPerMonthPrincipalInterest(invest, yearRate, month);System.out.println("等额本息---每月还款本息：" + perMonthPrincipalInterest);Map<Integer, BigDecimal> mapInterest = getPerMonthInterest(invest, yearRate, month);System.out.println("等额本息---每月还款利息：" + mapInterest);Map<Integer, BigDecimal> mapPrincipal = getPerMonthPrincipal(invest, yearRate, month);System.out.println("等额本息---每月还款本金：" + mapPrincipal);double count = getInterestCount(invest, yearRate, month);System.out.println("等额本息---总利息：" + count);double principalInterestCount = getPrincipalInterestCount(invest, yearRate, month);System.out.println("等额本息---应还本息总和：" + principalInterestCount);}
}

等额本金：

/*** Description:等额本金工具类* Copyright: Copyright (Corporation)2015* Company: Corporation* @author: 凯文加内特* @version: 1.0* Created at: 2015年12月1日 上午8:38:23* Modification History:* Modified by : */package com.utils;import java.math.BigDecimal;
import java.util.HashMap;
import java.util.Map;/*** 等额本金是指一种贷款的还款方式，是在还款期内把贷款数总额等分，每月偿还同等数额的本金和剩余贷款在该月所产生的利息，这样由于每月的还款本金额固定，* 而利息越来越少，借款人起初还款压力较大，但是随时间的推移每月还款数也越来越少。*/
public class AverageCapitalUtils {/*** 等额本金计算获取还款方式为等额本金的每月偿还本金和利息* * 公式：每月偿还本金=(贷款本金÷还款月数)+(贷款本金-已归还本金累计额)×月利率* * @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 每月偿还本金和利息,不四舍五入，直接截取小数点最后两位*/public static Map<Integer, Double> getPerMonthPrincipalInterest(double invest, double yearRate, int totalMonth) {Map<Integer, Double> map = new HashMap<Integer, Double>();// 每月本金double monthPri = getPerMonthPrincipal(invest, totalMonth);// 获取月利率double monthRate = yearRate / 12;monthRate = new BigDecimal(monthRate).setScale(6, BigDecimal.ROUND_DOWN).doubleValue();for (int i = 1; i <= totalMonth; i++) {double monthRes = monthPri + (invest - monthPri * (i - 1)) * monthRate;monthRes = new BigDecimal(monthRes).setScale(2, BigDecimal.ROUND_DOWN).doubleValue();map.put(i, monthRes);}return map;}/*** 等额本金计算获取还款方式为等额本金的每月偿还利息* * 公式：每月应还利息=剩余本金×月利率=(贷款本金-已归还本金累计额)×月利率* * @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 每月偿还利息*/public static Map<Integer, Double> getPerMonthInterest(double invest, double yearRate, int totalMonth) {Map<Integer, Double> inMap = new HashMap<Integer, Double>();double principal = getPerMonthPrincipal(invest, totalMonth);Map<Integer, Double> map = getPerMonthPrincipalInterest(invest, yearRate, totalMonth);for (Map.Entry<Integer, Double> entry : map.entrySet()) {BigDecimal principalBigDecimal = new BigDecimal(principal);BigDecimal principalInterestBigDecimal = new BigDecimal(entry.getValue());BigDecimal interestBigDecimal = principalInterestBigDecimal.subtract(principalBigDecimal);interestBigDecimal = interestBigDecimal.setScale(2, BigDecimal.ROUND_DOWN);inMap.put(entry.getKey(), interestBigDecimal.doubleValue());}return inMap;}/*** 等额本金计算获取还款方式为等额本金的每月偿还本金* * 公式：每月应还本金=贷款本金÷还款月数* * @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 每月偿还本金*/public static double getPerMonthPrincipal(double invest, int totalMonth) {BigDecimal monthIncome = new BigDecimal(invest).divide(new BigDecimal(totalMonth), 2, BigDecimal.ROUND_DOWN);return monthIncome.doubleValue();}/*** 等额本金计算获取还款方式为等额本金的总利息* * @param invest*            总借款额（贷款本金）* @param yearRate*            年利率* @param month*            还款总月数* @return 总利息*/public static double getInterestCount(double invest, double yearRate, int totalMonth) {BigDecimal count = new BigDecimal(0);Map<Integer, Double> mapInterest = getPerMonthInterest(invest, yearRate, totalMonth);for (Map.Entry<Integer, Double> entry : mapInterest.entrySet()) {count = count.add(new BigDecimal(entry.getValue()));}return count.doubleValue();}/*** @param args*/public static void main(String[] args) {double invest = 10000; // 本金int month = 12;double yearRate = 0.15; // 年利率Map<Integer, Double> getPerMonthPrincipalInterest = getPerMonthPrincipalInterest(invest, yearRate, month);System.out.println("等额本金---每月本息：" + getPerMonthPrincipalInterest);double benjin = getPerMonthPrincipal(invest, month);System.out.println("等额本金---每月本金:" + benjin);Map<Integer, Double> mapInterest = getPerMonthInterest(invest, yearRate, month);System.out.println("等额本金---每月利息:" + mapInterest);double count = getInterestCount(invest, yearRate, month);System.out.println("等额本金---总利息：" + count);}
}