Calculator.java

package myJourney;

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

public class Calculator {

	public static void main(String[] args) {
		final byte MONTHS_IN_A_YEAR = 12;
		final byte PERCENT = 100;
		
		Scanner scanner = new Scanner (System.in);
		
		System.out.print("Principal: ");
		int principal = scanner.nextInt();
		
		System.out.print("Annual Interest Rate: ");
		float annual_interest_rate = scanner.nextFloat();
		float monthly_interest = annual_interest_rate / PERCENT / MONTHS_IN_A_YEAR;
		
		System.out.print("Period (years) : ");
		byte period = scanner.nextByte();
		int number_of_payments = period * MONTHS_IN_A_YEAR;
		
		double mortgage = principal
						* (monthly_interest * Math.pow(1 + monthly_interest,number_of_payments))
						/ (Math.pow(1 + monthly_interest, number_of_payments) - 1);
		
		System.out.println("Mortgage : "+ NumberFormat.getCurrencyInstance().format(mortgage));
		}
	
	
}

just practice for primitive types ,and operators