if else?

I'm trying to get this calculator to show loan payment values even in the event of a 0% interest situation. Presently it just spits out NaN when I use values of 0. I'm guessing I could use an if else around the "return payment" to get it to try another formula if the original goes to zero. How would I write this?

Thanks,

J

Code:

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package com.direction.investor.financial.essentials;

import java.io.Serializable;
import java.text.DecimalFormat;

public class LoanCalculator implements Serializable {

       
        private static final long serialVersionUID = 1L;
        private double principal;
        private double annualRate;                // in percentage
        private int periodsPerYear;
        private int years;

        public static void main(String[] args) {
                LoanCalculator aCal = new LoanCalculator();
                aCal.setPrincipal(200000.0);
                aCal.setAnnualRate(8);                        // 8%
                aCal.setPeriodsPerYear(12);
                aCal.setYears(30);

                System.out.println("Payment=" + aCal.computePayment());
        }

        public double computePayment() {
                double payment = 0;
                int totalPeriods = years * periodsPerYear;

                payment = principal
                                * (annualRate/100)
                                / (periodsPerYear * (1.0 - Math.pow(1.0 + (annualRate/100)
                                                / periodsPerYear, -totalPeriods)));

                return payment;
        }

        public String[][] computeAmortization(){
                double balance=principal;
                double pmt=computePayment();
                int totalPeriods=years * periodsPerYear;
                double periodInterest=annualRate/(periodsPerYear*100);
                double cumulatedPmt=0;
                double cumulatedInterest=0;
                DecimalFormat aFormat=new DecimalFormat("#,##0.00;(#,##0.00)");
                String[][] aRtn=new String[totalPeriods][7];
                for(int i=0; i<totalPeriods; i++){
                        double periodInterestAmt=balance*periodInterest;
                        cumulatedPmt+=pmt-periodInterestAmt;
                        cumulatedInterest+=periodInterestAmt;
                        aRtn[i][0]=String.valueOf(i);
                        aRtn[i][1]=aFormat.format(balance);
                        aRtn[i][2]=aFormat.format(pmt-periodInterestAmt);
                        aRtn[i][3]=aFormat.format(periodInterestAmt);
                        aRtn[i][4]=aFormat.format(cumulatedPmt);
                        aRtn[i][5]=aFormat.format(cumulatedInterest);
                        balance=balance-(pmt-periodInterestAmt);
                        aRtn[i][6]=aFormat.format(balance);
                }
                return aRtn;
        }

        public double getPayment() {
                return computePayment();
        }

       
        public double getAnnualRate() {
                return annualRate;
        }

       
        public int getPeriodsPerYear() {
                return periodsPerYear;
        }

       
        public double getPrincipal() {
                return principal;
        }

       
        public int getYears() {
                return years;
        }

       
        public void setAnnualRate(double annualRate) {
                this.annualRate = annualRate;
        }

       
        public void setPeriodsPerYear(int periodsPerYear) {
                this.periodsPerYear = periodsPerYear;
        }

       
        public void setPrincipal(double principal) {
                this.principal = principal;
        }

       
        public void setYears(int years) {
                this.years = years;
        }

}

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Sounds like you're trying to divide by zero or something similar - I would put in a check for special cases (like the 0 case) or any other special edge cases.

Well your culprit is here:

payment = principal * (annualRate/100) / (periodsPerYear * (1.0 - Math.pow(1.0 + (annualRate/100) / periodsPerYear, -totalPeriods)));

But, what happens if the annual rate is negative? I would think you'd want to avoid that too.