/*

Programmer: Chris Gountanis

Date: 02/08/2008

Program Name: LoanCalculator.java for Week 3 IA

Description: Program asks user for input amount of the loan,

the interest rate and the number of years. The program

validates the input checking for valid numeric data before

continuing. If the interest rate was entered in percentage

form it converts to decimal before calculation process. The

program then calculates the monthly payment. Input values and

payment total are displayed rounded to the second decimal place.

*/

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

public class LoanCalculator {

public static void main(String[] args) throws IOException {

//declarations

BufferedReader dataIn = new BufferedReader(new InputStreamReader(System.in));

double payment=0, interestrate=0, loanamount=0, years=0;

String inputvalue="";

 

//get input for loan amount

while (!isNumeric(inputvalue)) {

System.out.println("Loan Amount? ");

inputvalue = dataIn.readLine();

}

loanamount = Float.parseFloat(inputvalue);

 

//get input for interest rate

inputvalue="";

while (!isNumeric(inputvalue)) {

System.out.println("What is the Annual Interest Rate? ");

inputvalue = dataIn.readLine();

}

interestrate = Float.parseFloat(inputvalue);

 

//get input for the number of years

inputvalue="";

while (!isNumeric(inputvalue)) {

System.out.println("How many Years? ");

inputvalue = dataIn.readLine();

}

years = Float.parseFloat(inputvalue);

 

//if the interest rate was entered in as percentage convert to decimal

if (interestrate > 1) {

interestrate = interestrate / 100;

}

 

//calculate the monthly payment total

payment = (interestrate * loanamount / 12) /

(1.0 - Math.pow(((interestrate / 12) + 1.0), (-(12 * years))));

 

//output the total and input values

System.out.print("\nThe Loan Amount:\t\t$" + loanamount);

System.out.print("\nThe Interest Rate:\t\t" + Round(interestrate * 100, 2) + "%");

System.out.print("\nThe Number of Years:\t\t" + years + " (Months: " + years * 12 + ")");

System.out.print("\n\nThe Monthly Payment:\t\t$" + Round(payment, 2));

}

 

//used to validate for numeric data

private static boolean isNumeric(String str){

try {

Float.parseFloat(str);

return true;

} catch (NumberFormatException nfe){

return false;

}

}

 

//used to round to a certain number of decimal places

public static float Round(double Rval, int Rpl) {

float p = (float)Math.pow(10, Rpl);

Rval = Rval * p;

float tmp = Math.round(Rval);

return (float)tmp/p;

}

}