Okay so basically I'm making a mortgage program and I'm supposed to ask the user if they would want to run the calculation again. It works for the most part, when i type in positive inputs, but when i enter a negative it doesn't ask the user. Also, there are lines under "y" and "userInput" that say the "variable is not used". How do i fix these problems, what's wrong with my code?! This program is due today so if comments can get straight to the point it would be greatly appreciated.

here is a pic of me inputting numbers and notice how when i type a negative number it doesnt ask to run again.

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and here is my code

package MortgageCalculation2b; import java.text.NumberFormat; import java.util.Scanner; /** * * @author Akira */ public class MortgageCalculation2b { /** * @param args the command line arguments */ public static void main(String[] args) { Scanner in = new Scanner(System.in); double loanAmount; double interestRate; double numberYears; double months; double monthlyPayment; double numerator; double denominator; double formula; boolean userInput; String y; String answer; while (userInput = true) { //prompt user for the loan amount System.out.print("Enter the loan amount: "); loanAmount = Double.parseDouble(in.nextLine()); //prompt the user for the interest rate System.out.print("Enter the rate: "); interestRate = Double.parseDouble(in.nextLine()); //prompt the user for thenumber of years System.out.print("Enter the number of years: "); numberYears = Double.parseDouble(in.nextLine()); //the number of years must be converted to months months = numberYears * 12; //if the user enters a negative number print out a error message, if not, continue calculations if ((loanAmount < 0) || (interestRate < 0) || (numberYears < 0)) { System.out.println("ALL NUMERICAL VALUES MUST BE POSITIVE!"); } else { //convert the interest rate interestRate = interestRate / 100 / 12; //numerator of the monthly payment formula numerator = Math.pow(1 + interestRate, months); //denominator of the monthly payment formula denominator = ((Math.pow(1 + interestRate, months))-1); //the formula equals the numerator divided by the denominator formula = ( numerator / denominator ); //monthly payment calculation monthlyPayment = (interestRate * loanAmount * formula); //sytem output NumberFormat defaultFormat = NumberFormat.getCurrencyInstance(); System.out.println("The monthly payment is: " + defaultFormat.format(monthlyPayment)); //prompt the user if they would like to calculate the program again. System.out.println("Would you like to calculate again (y/n) : "); //if the user enters "y" the program will run again and if the user enters anything else it ends answer = in.nextLine(); answer = answer.toLowerCase(); if ( answer.equals("y")) userInput = true; else{ break; } } } }}