Loan Payment Calculator with Interest, Principal, and Balance

Loan_Payment_Calculator.java

+// Program:	Loan_Payment_Calculator.java
+// Purpose: This program calculates monthly loan payments including interest.
+// Author:	Brian Vojtko	
+// Date:	10/24/2018
+import java.text.DecimalFormat;
+import java.util.Scanner;
+
+public class Loan_Payment_Calculator {
+
+	public static void main(String[] args){
+	
+		//Make outputs in 2 decimals
+		DecimalFormat money = new DecimalFormat(".00");
+		
+		char decision = 'y';
+		
+		//Loops program if user responded with 'y'
+		while (decision == 'y' || decision == 'Y') {
+		
+		Scanner input = new Scanner(System.in);
+	
+		//Integers
+		double interestPercent;
+		double monthlyRate;
+		double totalInterest = 0;
+		double payment;
+		
+	//User Introduction
+	System.out.println("   Loan Payment Calculator");
+	System.out.println("*********************************");
+	
+	//Amount user owes
+	System.out.println("Enter the initial loan amount: ");
+	double amount = input.nextDouble ();
+	
+		//Error Loop
+		while (amount > 1000000) {
+			System.out.println("the loan amount cannot exceed $1,000,000. Try again.");
+			amount = input.nextDouble();
+			continue;
+		}
+	
+		//Error Loop
+		while (amount <= 0) {
+			System.out.println("You must enter a value greater than zero. Try again.");
+			amount = input.nextDouble();
+			continue;
+		}
+	
+	//Annual Interest Rate
+	System.out.println("Enter the annual interest rate (as a percentage): ");
+	interestPercent = input.nextDouble();
+	
+	//Calculate Monthly Interest Rate
+	monthlyRate = (interestPercent / 100) / 12;
+	
+		//Error Loop
+		while (interestPercent < 2 || interestPercent > 15) {
+			System.out.println("You must enter a value between 2.0 and 15.0 (inclusive). Try again.");
+			interestPercent = input.nextDouble();
+			continue;
+		}
+	
+	//Amount of years user has to repay
+	int years;
+	System.out.println("Enter the term of the loan in years: ");
+	years = input.nextInt();
+	
+		//Error Loop
+		while (years <= 0 || years > 30) {
+			System.out.println("Please enter a term between 1-30 years.");
+			years = input.nextInt();
+			continue;
+		}
+		
+	//Monthly Payment Calculation
+	double m = (years * 12);	
+	payment = (amount * monthlyRate) / (1 - Math.pow(1 + monthlyRate, -m));
+	
+	//Monthly Payment output
+	System.out.println("Your monthly payment is: $" + money.format(payment));
+	
+	//Line space
+	System.out.println("");
+	
+	//Beginning of Loan Chart
+	System.out.println("Month\t\tInterest\tPrincipal\tBalance");
+	System.out.println("----------------------------------------------------------");
+	
+	//Loan Chart Calculation
+	double balance = amount, principal, interest;
+	
+	for (int i = 1; i <= m; i++) {
+		interest = monthlyRate * balance;
+		principal = payment - interest;
+		balance = balance - principal;
+		totalInterest += interest;
+	
+		//User output
+		System.out.println(i + "\t\t" + "$" + money.format(interest) + "\t\t" + "$" + money.format(principal) + "\t\t" + "$" + money.format(balance));
+	}
+
+	//User output for total amount of interest paid
+	System.out.println("");
+	System.out.println("The total amount of interest paid is: $" + money.format(totalInterest));
+	System.out.println("");
+	
+	//Repeat Loop
+	boolean yesDecision;
+	boolean noDecision;
+	input.nextLine();
+	
+	do {
+		System.out.println("Do you have another loan to process? (y/n): ");
+		decision = input.nextLine().charAt(0);
+		yesDecision = (decision == 'y' || decision == 'Y');
+		noDecision = (decision == 'n' || decision == 'N');
+	} while(!(yesDecision || noDecision));
+		
+		System.out.println("");
+	}
+	System.out.println("Thank you for using our loan calculator. Goodbye!");
+}
+}