Java Loan Amortization

Question

Please what could be wrong with my code. it is an iteration approach to: The monthly payment for a given loan pays the principal and the interest. The monthly interest is computed by multiplying the monthly interest rate and the balance (the remaining principal). The principal paid for the month is therefore the monthly payment minus the monthly interest. Write a program that lets the user enter the loan amount, number of years, and interest rate and displays the amortization schedule for the loan. However, i keep getting NaN just to calculate monthly payment.code is as follow:

import java.util.Scanner;
public class Amortization {
public static void main(String[] args) {
//create Scanner 
Scanner s = new  Scanner(System.in);
//prompt Users  for  input
System.out.print("Enter loan Amount:");
int  loanAmount = s.nextInt();
System.out.print("Enter numberof Years:");
int numberYear =s.nextInt();
System.out.print("Enter Annual Interest Rate:");
int annualRate = s.nextInt();

double monthlyrate= annualRate/1200;
double monthlyPayment = loanAmount*monthlyrate/(1 -1/Math.pow(1+monthlyrate,numberYear*12));


System.out.printf("%6.3f",monthlyPayment);


// TODO code application logic here
}

}

Answer 1

I just wrote code for a similar problem. I share with you my solution. I got a lot of ideas from http://java.worldbestlearningcenter.com/2013/04/amortization-program.html

public class LoanAmortizationSchedule {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        // Prompt the user for loan amount, number of years and annual interest rate

        System.out.print("Loan Amount: ");
        double loanAmount = sc.nextDouble();

        System.out.print("Number of Years: ");
        int numYears = sc.nextInt();

        System.out.print("Annual Interest Rate (in %): ");
        double annualInterestRate = sc.nextDouble();

        System.out.println();  // Insert a new line

        // Print the amortization schedule

        printAmortizationSchedule(loanAmount, annualInterestRate, numYears);
    }

    /**
     * Prints amortization schedule for all months.
     * @param principal - the total amount of the loan
     * @param annualInterestRate in percent
     * @param numYears
     */
    public static void printAmortizationSchedule(double principal, double annualInterestRate,
                                                 int numYears) {
        double interestPaid, principalPaid, newBalance;
        double monthlyInterestRate, monthlyPayment;
        int month;
        int numMonths = numYears * 12;

        // Output monthly payment and total payment
        monthlyInterestRate = annualInterestRate / 12;
        monthlyPayment      = monthlyPayment(principal, monthlyInterestRate, numYears);
        System.out.format("Monthly Payment: %8.2f%n", monthlyPayment);
        System.out.format("Total Payment:   %8.2f%n", monthlyPayment * numYears * 12);

        // Print the table header
        printTableHeader();

        for (month = 1; month <= numMonths; month++) {
            // Compute amount paid and new balance for each payment period
            interestPaid  = principal      * (monthlyInterestRate / 100);
            principalPaid = monthlyPayment - interestPaid;
            newBalance    = principal      - principalPaid;

            // Output the data item
            printScheduleItem(month, interestPaid, principalPaid, newBalance);

            // Update the balance
            principal = newBalance;
        }
    }

    /**
     * @param loanAmount
     * @param monthlyInterestRate in percent
     * @param numberOfYears
     * @return the amount of the monthly payment of the loan
     */
    static double monthlyPayment(double loanAmount, double monthlyInterestRate, int numberOfYears) {
        monthlyInterestRate /= 100;  // e.g. 5% => 0.05
        return loanAmount * monthlyInterestRate /
                ( 1 - 1 / Math.pow(1 + monthlyInterestRate, numberOfYears * 12) );
    }

    /**
     * Prints a table data of the amortization schedule as a table row.
     */
    private static void printScheduleItem(int month, double interestPaid,
                                          double principalPaid, double newBalance) {
        System.out.format("%8d%10.2f%10.2f%12.2f\n",
            month, interestPaid, principalPaid, newBalance);
    }

    /**
     * Prints the table header for the amortization schedule.
     */
    private static void printTableHeader() {
        System.out.println("\nAmortization schedule");
        for(int i = 0; i < 40; i++) {  // Draw a line
            System.out.print("-");
        }
        System.out.format("\n%8s%10s%10s%12s\n",
            "Payment#", "Interest", "Principal", "Balance");
        System.out.format("%8s%10s%10s%12s\n\n",
            "", "paid", "paid", "");
    }
}

Answer 2

That's because you are entered number followed by an enter . So your nextLine method call just reads return key while nextInt just reads integer value ignoring the return key. To avoid this issue:

Just after reading input, you call something like:

int loanAmount=s.nextInt();
s.nextLine();//to read the return key.

Also, it might be a good idea to format your code (identation)