Amortization

import java.io.*;
import java.math.*;
import java.text.DecimalFormat;

public class Amortization {

    private double loanAmount;
    private double interestRate;
    private double loanBalance;
    private double term;
    private double payment;
    private int loanYears;

    public Amortization(double loan, double rate, int years) {
        this.loanAmount = loan;
        this.loanBalance = loan;
        this.interestRate = rate;
        this.loanYears = years;

        calcPayment();
    }

    private void calcPayment() {
        this.term = Math.pow(interestRate / 12 + 1, loanYears * 12);
        this.payment = (loanAmount * (interestRate / 12.0) * term) / (term - 1);
    }

    public int getNumberOfPayments() {
        return (loanYears * 12);
    }

    public double getLoanAmount() {
        return loanAmount;
    }

    public double getInterestRate() {
        return interestRate;
    }

    public int getLoanYears() {
        return loanYears;
    }

    public void saveReport(String filename) throws FileNotFoundException {
        DecimalFormat df = new DecimalFormat("0.00");
        File file = new File(filename);
        PrintWriter pw = new PrintWriter(file);
        pw.println("Monthly Payment: $" + df.format(payment));
        pw.println("Month\tInterest\tPrincipal\tBalance");
        pw.println("-----------------------------------------------");
        for (int i = 0; i < getNumberOfPayments(); i++) {
            double interest = interestRate / 12.0
                    * loanBalance;
            double principal = payment - interest;
            loanBalance -= principal;
            pw.println((i + 1) + "\t" + df.format(interest) + "\t\t"
                    + df.format(principal) + "\t\t" + df.format(loanBalance));
        }

        pw.close();

    }
}