/**
 * This program calculates the mortgage payment for a loan with a principal
 * value of $200,000, 30 year term, and an annual percentage rate of 5.75%.
 * Author - Tom Rhoads
 */

public class MortgageCalculator {
    public static void main(String args[]) {
        /*
         * this line declares the principalvalue of the loan
         */
        double principalValue;

        /*
         * this line declares the interestrate of the loan
         */
        double interestRate;

        /*
         * this line declares the annualpercentage rate of the loan
         */
        double apr;

        /*
         * this line declares the term of theloan in months
         */
        int term;

        /*
         * this line declares the monthlypayment of the loan
         */
        double monthlyPayment;

        /*
         * $200,000 is the principal value of the loan
         */
        principalValue = 240000;

        apr = 6.0; // 5.75% is the annual percentage rate
        interestRate = apr / 100 / 12; // Formula for interest rate by month
        term = 360; // 30 year loan is 360 months

        monthlyPayment = calculateMonthlyPayment(principalValue, interestRate,
                term);

        printAmortizationTable(monthlyPayment, term, principalValue,
                interestRate);

    }

    /*
     * Formula for calculating monthly payments on a mortgage
     */
    private static double calculateMonthlyPayment(double principalValue,
            double interestRate, int term) {

        return (principalValue * interestRate)
                / (1 - Math.pow(1 + interestRate, -term));
    }

    /**
     * Prints the amortization table.
     */
    private static void printAmortizationTable(double payment, int term,
            double principalBalance, double interestRate) {

        /** initialize the balances **/
        double loanBalance = term * payment;
        double interestBalance = loanBalance - principalBalance;
        double totalPrincipalPaid = 0;
        double totalInterestPaid = 0;

        /**
         * Prints the header of the table.
         */
        System.out.printf("%20s\t%25s\t%20s\n", "Balance",
                "Interest Paid This Month", "Total Interest Paid");

        /** step through all the payment periods */
        for (int paymentNumber = 1; paymentNumber <= term; paymentNumber++) {
            /**
             * The portion of the payment that goes to interest is based on the
             * remaining principal balance.
             **/
            double interestPaidThisMonth = interestRate * principalBalance;

            /**
             * The rest of the payment goes to principal.
             **/
            double principalPaidThisMonth = payment - interestPaidThisMonth;

            /**
             * Update the remaining balances and total paid values
             **/
            loanBalance = loanBalance - payment;
            principalBalance = principalBalance - principalPaidThisMonth;
            totalPrincipalPaid = totalPrincipalPaid + principalPaidThisMonth;
            interestBalance = interestBalance - interestPaidThisMonth;
            totalInterestPaid = totalInterestPaid + interestPaidThisMonth;

            /**
             * Prints a row of the table.
             */
            System.out.printf("%20.2f\t%25.2f\t%20.2f\n", principalBalance,
                    interestPaidThisMonth, totalInterestPaid);
        }

    }
}