Q : Not understanding loop process? or possible if statements?

Question

I am working on a project that involves creating a rental car calculator.

What I am trying to do is make it to where when asked: "What vehicle would you like to rent??". If a number that is not between 1-3 is entered when the user is prompted this, then I want the program to loop back to the point of being asked vehicle type again.

Similarly, when prompted for 'Please enter the number of days rented. (Example; 3) : ' I want to only allow the user to input whole positive numbers. for instance, not allowing input of 3.1, 2.35, 0.35 -2 and, etc...

here is what I have written and my attempt at these questions :

package inter;

import java.util.Scanner;

public class Inter {
    public static void main(String []args){
        int count=0;
        int days;
        double DailyFee=0, NontaxTotal, CarType, Total,FullTotal=0;
        Scanner in=new Scanner(System.in);
        System.out.println("If there are any customer press 1 else press 0");
        int cus=in.nextInt();

        while(cus!=0){
            count++;
            System.out.print("What vehical would you like to rent?\n");
            System.out.println("Enter 1 for an economy car\n");
            System.out.println("Enter 2 for a sedan car\n");
            System.out.println("Enter 3 for an SUV");
            CarType = in.nextInt();
            if (CarType == 1) {
                  DailyFee=31.76;
            }
            else if(CarType == 2) {
                  DailyFee=40.32;
            }
            else if(CarType == 3) {
                  DailyFee=47.56;
            }
            else if(CarType <= 0) {
                System.out.println("input is not a positive Integer ");
                System.out.println("Please enter a positive integer value: ");
                cus = 0; }
            else if(CarType > 4) {
                System.out.println("input is not a positive Integer ");
                System.out.println("Please enter a positive integer value: ");
                cus = 0; }

            System.out.print("Please enter the number of days rented. (Example; 3) : ");
            days = Integer.valueOf(in.nextLine());
            double x=days;
            NontaxTotal = (DailyFee * x);
            Total = (NontaxTotal * 1.06);
            FullTotal+=Total;

            System.out.printf("The total amount due is $ %.2f \n",Total);

            System.out.println("If there are any customer press 1 else press 0");
            cus=in.nextInt();
        }
        System.out.println("Count of customers : "+count);
        System.out.printf("Total of the Day : $ %.2f",FullTotal);
    }   
}

Answer 1

Let me help you with this, I made this code for you, i tried it and it worked this will check if both answers were whole numbers (integers) and more than zero and will also check if the answer was numeric in the first place so that if the user answered with letters he will be prompted to try again This is my suggestion: basically i used the try-catch block with InputMismatchException to detect if the answer was not an integer (whole number ) or was not numeric at all, every time a mistake is detected i flip a boolean to false and keep looping as long as this boolean is false (i flip the boolean back to true before checking otherwise once the user gives a wrong answer he will always be prompted to answer even if he gave a correct answer after)

    int vehicleType;
    int numberOfDays;
    double dailyFee;
    boolean validAnswer1 = false;
    boolean validAnswer2 = false;

    Scanner scan = new Scanner(System.in);

    while (validAnswer1 == false) {
        validAnswer1 = true;
        System.out.println("Choose Vehicle Type");
        try {
            vehicleType = scan.nextInt();
            if (vehicleType <= 0) {
                System.out.println("Number must be more than zero");
                validAnswer1 = false;
            } else if (vehicleType >= 4) {
                System.out.println("Number should be from 1 to 3");
                validAnswer1 = false;
            } else {
                if (vehicleType == 1) {
                    dailyFee=31.76;
                } else if(vehicleType == 2) {
                    dailyFee=40.32;
                }else if(vehicleType == 3) {
                    dailyFee=47.56;
                }
                while (validAnswer2 == false) {
                    validAnswer2 = true;
                    try {
                        System.out.println("Enter number of days rented ?");
                        numberOfDays = scan.nextInt();
                        if (numberOfDays <= 0) {
                            System.out.println("Number of days must be more than zero");
                            validAnswer2 = false;
                        } else {
                            // calculate your rent total here
                        }
                    } catch(InputMismatchException ex) {
                        System.out.println("Answer must be an Integer");
                        validAnswer2 = false;
                        scan.next();
                    }
                }                   
            }
        } catch (InputMismatchException ex) {
            validAnswer1 = false;
            System.out.println("Answer must be an Integer");     
            scan.next();
        }           
    }

Hope this was useful, do let me know if you still need help