“50”计划

1、目标

实现50万的存款目标，俗称 “50计划”。

    private static int targetAmount = 500000;

2、时间

达成这个目标，我们将在第xxxx年xx月实现？⌛

答案：文末给出了结果。

3、因数

纳入考虑的可变因素，目前列举了7项：投资年化率、工资、收房租、年终奖、生活费、付房租、贷款月供。

不纳入考虑的因素：生病、意外事故、工资不固定的情况，此类不太适用，误差较大。

    private static double yearRate = 0.10;

    //income
    private static int wages = 9200;
    private static int rentCollect = 0;
    private static int yearEndAward = 20000;

    //payout
    private static int livingCost = 800;
    private static int rent = 800;
    private static int monthlyPayment = 0;

4、达成

这是一个算法，通过修改7项可变因素，将会得出具有参考价值的数据。
计算的核心就是利用复利效应，充分发挥资金价值。

源代码如下：

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Test {
    public static BigDecimal MONTHS_A_YEAR = new BigDecimal(12);
    public static BigDecimal MONTHS_TWO_YEAR = new BigDecimal(24);

    private static int targetAmount = 500000;
    private static double yearRate = 0.10;

    //income
    private static int wages = 9200;
    private static int rentCollect = 0;
    private static int yearEndAward = 20000;

    //payout
    private static int livingCost = 800;
    private static int rent = 800;
    private static int monthlyPayment = 0;


    private static List<Map<BigDecimal, BigDecimal>> yearAmountMap = new ArrayList<>();
    private static List<Map<BigDecimal, BigDecimal>> monthAmountMap = new ArrayList<>();

    public static void main(String[] args) {

        BigDecimal yearRemainIncome = getYearRemainIncome();

        gotoAchieveGoals(yearRemainIncome);
    }

    private static BigDecimal getYearRemainIncome() {

        int remainWages = wages - livingCost - rent - monthlyPayment;

        BigDecimal remainWagesBd = new BigDecimal(remainWages);
        BigDecimal yearEndAwardBd = new BigDecimal(yearEndAward);
        BigDecimal rentCollectBd = new BigDecimal(rentCollect);

        BigDecimal yearWageBd = remainWagesBd.multiply(MONTHS_A_YEAR);
        BigDecimal yearRentBd = rentCollectBd.multiply(MONTHS_A_YEAR);

        BigDecimal yearWageAndRent = yearWageBd.add(yearRentBd);
        BigDecimal yearWageAndRentAndYearEndAward = yearWageAndRent.add(yearEndAwardBd);

        return yearWageAndRentAndYearEndAward;
    }

    private static void gotoAchieveGoals(BigDecimal yearRemainIncome) {
        yearAmountMap.clear();
        BigDecimal targetAmount = new BigDecimal(Test.targetAmount);

        BigDecimal monthRemainIncome = yearRemainIncome.divide(MONTHS_A_YEAR, 2, BigDecimal.ROUND_HALF_UP);

        BigDecimal achieveGoalsTotalMonths = targetAmount.divide(monthRemainIncome, 2, BigDecimal.ROUND_HALF_UP);

        BigDecimal achieveGoalsTotalYears = achieveGoalsTotalMonths.divide(MONTHS_A_YEAR, 2, RoundingMode.HALF_UP);

        BigDecimal investmentAndPrincipalTotalAmount = getInvestmentAndPrincipalTotalAmount(yearRemainIncome, achieveGoalsTotalMonths);

        BigDecimal totalInvestmentIncomeAmount = investmentAndPrincipalTotalAmount.subtract(targetAmount);

        double achieveGoalsWhereYear = getAchieveGoalsWhereYear();


        System.out.println("--------------Total Result--------------");

        System.out.println(" A year fixed income : " + yearRemainIncome);

        System.out.println(" Total investment income : " + totalInvestmentIncomeAmount);
        System.out.println(" Total principal income : " + investmentAndPrincipalTotalAmount.subtract(totalInvestmentIncomeAmount));
        System.out.println(" Total investment and principal income : " + investmentAndPrincipalTotalAmount);

        System.out.println(" Total year achieving target by fixed income : " + achieveGoalsTotalYears);
        System.out.println(" Total year achieving target by fixed and investment income : " + achieveGoalsWhereYear);
    }


    private static BigDecimal getInvestmentAndPrincipalTotalAmount(BigDecimal principal, BigDecimal achieveGoalsTotalMonths) {

        BigDecimal yearRateBd = new BigDecimal(yearRate);
        yearRateBd = yearRateBd.setScale(2, RoundingMode.HALF_UP);

        BigDecimal monthRate = yearRateBd.divide(MONTHS_TWO_YEAR, 6, BigDecimal.ROUND_HALF_UP);
        monthRate = monthRate.setScale(4, RoundingMode.HALF_UP);

        double yearAccumulateAmount = getYearAccumulateAmount(principal, achieveGoalsTotalMonths, yearRateBd);

        double yearRemainMonthAccumulateAmount = getYearRemainMonthAccumulateAmount(principal, new BigDecimal(yearAccumulateAmount), achieveGoalsTotalMonths, monthRate);

        BigDecimal accumulateAmountBd = new BigDecimal(yearAccumulateAmount + yearRemainMonthAccumulateAmount);

        accumulateAmountBd = accumulateAmountBd.setScale(2, RoundingMode.HALF_UP);

        return accumulateAmountBd;
    }

    private static double getYearAccumulateAmount(BigDecimal principal, BigDecimal totalMonths, BigDecimal yearRate) {
        System.out.println("--------------year_rate（" + yearRate + "）--------------");

        int year = totalMonths.setScale(0, RoundingMode.HALF_UP).intValue() / 12;
        BigDecimal yearAccumulateAmount = new BigDecimal(0);
        BigDecimal investmentAndPrincipalAmount;
        for (int i = 1; i <= year; i++) {
            if (i == 1) {
                investmentAndPrincipalAmount = principal;
            } else {
                investmentAndPrincipalAmount = yearAccumulateAmount;
            }
            BigDecimal yearInvestmentIncome = investmentAndPrincipalAmount.multiply(yearRate).setScale(2, RoundingMode.HALF_UP);

            yearAccumulateAmount = yearAccumulateAmount.add(principal.add(yearInvestmentIncome));

            System.out.println("The " + i + " year, yearAccumulateAmount - yearInvestmentIncome = " + yearAccumulateAmount + " - " + yearInvestmentIncome + " = " + (yearAccumulateAmount.subtract(yearInvestmentIncome).doubleValue()));

            HashMap<BigDecimal, BigDecimal> map = new HashMap<>();
            map.put(BigDecimal.valueOf(i), yearAccumulateAmount);
            yearAmountMap.add(map);
        }
        return yearAccumulateAmount.doubleValue();
    }


    private static double getYearRemainMonthAccumulateAmount(BigDecimal principal, BigDecimal originYearAccumulateAmount, BigDecimal achieveGoalsTotalMonths, BigDecimal monthRate) {
        System.out.println("--------------remain_month_rate（" + monthRate + "）--------------");

        BigDecimal monthFixedIncome = principal.divide(MONTHS_A_YEAR, 2, RoundingMode.HALF_UP);

        int remainMonths = achieveGoalsTotalMonths.intValue() % 12;

        BigDecimal yearAccumulateAmountBd = originYearAccumulateAmount;
        yearAccumulateAmountBd = yearAccumulateAmountBd.setScale(2, RoundingMode.HALF_UP);

        BigDecimal targetYearAccumulateAmount = yearAccumulateAmountBd;

        BigDecimal yearRemainMonthAccumulateAmount;

        for (int i = 1; i <= remainMonths; i++) {

            yearRemainMonthAccumulateAmount = targetYearAccumulateAmount;
            yearRemainMonthAccumulateAmount = yearRemainMonthAccumulateAmount.setScale(2, RoundingMode.HALF_UP);

            BigDecimal monthInvestmentIncome = yearRemainMonthAccumulateAmount.multiply(monthRate).setScale(2, RoundingMode.HALF_UP);

            BigDecimal fixedInvestmentIncome = (monthFixedIncome.add(monthInvestmentIncome));

            targetYearAccumulateAmount = targetYearAccumulateAmount.add(fixedInvestmentIncome);

            System.out.println("The remain month" + i + " ," + " targetYearAccumulateAmount - monthInvestmentIncome = " + " " + targetYearAccumulateAmount + " - " + monthInvestmentIncome + " = " + (targetYearAccumulateAmount.subtract(monthInvestmentIncome).doubleValue()));

            HashMap<BigDecimal, BigDecimal> map = new HashMap<>();
            map.put(BigDecimal.valueOf(i), targetYearAccumulateAmount);
            monthAmountMap.add(map);
        }
        return targetYearAccumulateAmount.subtract(yearAccumulateAmountBd).doubleValue();
    }

    public static double getAchieveGoalsWhereYear() {
        BigDecimal targetAmountBd = new BigDecimal(targetAmount);
        targetAmountBd = targetAmountBd.setScale(2, RoundingMode.HALF_UP);

        double totalYear = yearAmountMap.size();

        for (Map<BigDecimal, BigDecimal> map : yearAmountMap) {
            for (Map.Entry<BigDecimal, BigDecimal> entry : map.entrySet()) {
                if (entry.getValue().compareTo(targetAmountBd) >= 0) {
                    return entry.getKey().doubleValue();
                }
            }
        }
        //year amount is not enough,so find the month
        for (Map<BigDecimal, BigDecimal> map : monthAmountMap) {
            for (Map.Entry<BigDecimal, BigDecimal> entry : map.entrySet()) {
                if (entry.getValue().compareTo(targetAmountBd) >= 0) {
                    return totalYear + (entry.getKey().divide(MONTHS_A_YEAR, 2, RoundingMode.HALF_UP)).doubleValue();
                }
            }
        }

        double month = BigDecimal.valueOf(monthAmountMap.size()).divide(MONTHS_A_YEAR, 2, RoundingMode.HALF_UP).doubleValue();
        return totalYear + month;
    }
}

输出：

--------------year_rate（0.10）--------------
The 1 year, totalIncome - investmentIncomeBd = 122320.00 - 11120.00 = 111200.0
The 2 year, totalIncome - investmentIncomeBd = 245752.00 - 12232.00 = 233520.0
The 3 year, totalIncome - investmentIncomeBd = 381527.20 - 24575.20 = 356952.0
The 4 year, totalIncome - investmentIncomeBd = 530879.92 - 38152.72 = 492727.2
--------------remain_month_rate（0.0042）--------------
The remain month1 , totalIncome - investmentIncomeBd =  542376.29 - 2229.70 = 540146.59
The remain month2 , totalIncome - investmentIncomeBd =  553920.94 - 2277.98 = 551642.96
The remain month3 , totalIncome - investmentIncomeBd =  565514.08 - 2326.47 = 563187.61
The remain month4 , totalIncome - investmentIncomeBd =  577155.91 - 2375.16 = 574780.75
The remain month5 , totalIncome - investmentIncomeBd =  588846.63 - 2424.05 = 586422.58
--------------Total Result--------------
 A year fixed income : 111200
 Total investment income : 88846.63
 Total principal income : 500000.00
 Total investment and principal income : 588846.63
 Total year achieving target by fixed income : 4.50
 Total year achieving target by fixed and investment income : 4.0

111200：一年能攒下的金额；

88846.63：投资收入总金额；

4.50：只拿固定工资不投资需要4年半才能达成目标；

4.0：通过固定工资和投资理财则只需要4年即可达成目标；

要不要去看看自己的情况，那就去编译源码，修改7项可变因素吧。

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