Mortgage_Calculator.java

import java.text.NumberFormat;
import java.util.Scanner;

public class Mortgage_Calculator {
    public static void main(String[] args) {
        final byte MONTHS_IN_YEAR = 12;
        final byte PERCENT = 100;

        int principal = 0;
        float annualInterestRate = 0;
        int numberOfPayments = 0;

        Scanner scanner = new Scanner(System.in);

        while (true) {
            System.out.print("Principal: ");
            principal = scanner.nextInt();
            if (principal >= 1000 && principal <= 1_000_000_000) {
                break;
            } else {
                System.out.println("Enter a value between 1000 and 1000000000");
            }
        }

        while (true) {
            System.out.print("Annual Interest Rate: ");
            annualInterestRate = scanner.nextFloat();
            if (annualInterestRate >= 1 && annualInterestRate <= 30) {
                break;
            }
            System.out.println("Enter a value between 1 and 30.");
        }

        float monthlyInterestRate = annualInterestRate / PERCENT / MONTHS_IN_YEAR;
        while (true) {
            System.out.print("Period (Years): ");
            byte years = scanner.nextByte();
            if (years >= 1 && years <= 30) {
                numberOfPayments = years * MONTHS_IN_YEAR;
                break;
            }
            System.out.println("Enter a value between 1 and 30.");
        }

        double mortgage = principal * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments))
                / (Math.pow(1 + monthlyInterestRate, numberOfPayments) - 1);

        String mortgageFormatted = NumberFormat.getCurrencyInstance().format(mortgage);
        System.out.println("Mortgage: " + mortgageFormatted);
    }
}