How to restrict input from user to a numeric value?

Question

I've been searching on the internet and can't seem to find this answer So does anyone know to how stop users from inputting letters where only numbers should be allowed?

This is what my code looks like so far.

public static double payCalculator(double hours, double basePay)
{
    double totalPay; 
    double overTime = 8.00 * 1.5;
    while(hours < 0 | hours > 60) {
        System.out.println("Cannot work more than 60 hours a week");
        System.out.println("Hours Work?");
        hours = in.nextDouble();
    }
    while(basePay < 8) {
        System.out.println("Base Pay cannot be less than 8");
        System.out.println("Base Pay?");
        basePay = in.nextDouble();
    }
    if 
        (hours <= 40){
        totalPay = hours*basePay;
    }
    else {
        totalPay = ((hours - 40)*overTime) + (40*basePay);
    }
    return totalPay;

}
public static void main (String[] args) {

    System.out.println("Hours worked?");
    hours = in.nextDouble();
    System.out.println("Base Pay?");
    basePay = in.nextDouble();
    DecimalFormat df = new DecimalFormat("###.##");
    totalPay = payCalculator(hours, basePay);
    System.out.println("Total Pay is " + df.format(totalPay));       
}
}

Thank you for your time.

You don't need to post your entire code to find the solution to your problem, please share only that part of your code which is related to your problem. — Sufiyan Ghori
– Sufiyan Ghori, Commented Jan 30, 2015 at 13:17
Seems to be a console application. Is a GUI with Swing input text field possible. — PeterMmm
– PeterMmm, Commented Jan 30, 2015 at 13:23
Sufiyan Ghori - all the code is related to my problem, I'm not sure where the answer would go. — Korwynn Wagstaff
– Korwynn Wagstaff, Commented Jan 30, 2015 at 13:35
@KorwynnWagstaff, not all the code is related, for instance, code in your main method is enough to understand what you are asking for, therefore there was no need to include payCalculator() method with your code. — Sufiyan Ghori
– Sufiyan Ghori, Commented Jan 30, 2015 at 14:18

Sufiyan Ghori · Accepted Answer · 2015-01-30 13:48:51Z

I assume your are using Scanner to take input.

You can use Scanner.hasNextDouble() to verify it is the number, it returns true if the next token in this scanner's input can be interpreted as a double value using the nextDouble() method. The scanner does not advance past any input.

Consider this example, It will keep asking for the input unless the user provides it with a number,

    Scanner sc = new Scanner(System.in);
    double dbl = 0.0;
    boolean isValid = false;
    while (isValid == false) {
        System.out.println("Input Number: ");
        // If input is number execute this,
        if (sc.hasNextDouble()) {
            dbl = sc.nextDouble();
            isValid = true;
            System.out.println("OK");
        }
        // If input is not a number execute this block, 
        else {
            System.out.println("Error! Invalid number. Try again.");
        }
        sc.nextLine(); // discard any other data
    }
    sc.close();

output,

Input Number: 
adsads
Error! Invalid number. Try again.
Input Number: 
sdas
Error! Invalid number. Try again.
Input Number: 
hello
Error! Invalid number. Try again.
Input Number: 
hi
Error! Invalid number. Try again.
Input Number: 
2.0
OK

Collectives™ on Stack Overflow

How to restrict input from user to a numeric value?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related