if else?

[johnsonjp34]

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

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;
	}

}

[quad64bit]

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.

[SJF]

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.