How to use scanner to accept only int or prevent users from inputting double? [duplicate]

Question

This is my current code. What I would like to do is limit the users input to only int. If a double is entered, I'd like a line printed "Please enter a whole number." I've tried to play around with scanner.hasNextint but haven't had much success. Is there a way to ignore double as an input entirely and have it round?

Thanks in advance!

public class BMI extends DecimalFormat{ public static void main(String[] args) { int weight; int height; double bodyMassIndex; DecimalFormat dfWithTwoDecimalPlaces; Scanner scanner; scanner = new Scanner(System.in); System.out.print("What is your weight in kilograms (kg): "); weight = scanner.nextInt(); System.out.print("What is your height in centimeters(cm): " ); height = scanner.nextInt(); bodyMassIndex = (weight / Math.pow(height/100.0, 2.0) ); dfWithTwoDecimalPlaces = new DecimalFormat ("0.00"); System.out.print("Your Body Mass Index is: " + dfWithTwoDecimalPlaces.format(bodyMassIndex)); } }

mmuzahid · Accepted Answer · 2016-01-18 09:32:06Z

Create a user defined method getNextInt() as bellow:

/**get next integer*/ public static int getNextInt(Scanner scanner) { while (!scanner.hasNextInt()) { scanner.next(); } return scanner.nextInt(); } public static void main(String[] args) { int weight; int height; double bodyMassIndex; DecimalFormat dfWithTwoDecimalPlaces; Scanner scanner; scanner = new Scanner(System.in); System.out.print("What is your weight in kilograms (kg): "); weight = getNextInt(scanner);//call user-defined method System.out.print("What is your height in centimeters(cm): " ); height = getNextInt(scanner);//call user-defined method bodyMassIndex = (weight / Math.pow(height/100.0, 2.0) ); dfWithTwoDecimalPlaces = new DecimalFormat ("0.00"); System.out.print("Your Body Mass Index is: " + dfWithTwoDecimalPlaces.format(bodyMassIndex)); }

You can add a message inside while loop like this:

while (!scanner.hasNextInt()) { scanner.next(); System.out.println("Please enter a whole number");//message }

This didn't work for me but I didn't have time to fully try and work out the errors that were returned. The assignment that I have didn't call for this, however I had to turn it in, so I turned it in as is and will continue to work on this in my freetime. I appreciate everyones response! Thank you! Ill reply if I get stuck and ill post the errors that I have.

sh. park · Accepted Answer · 2016-01-18 09:04:49Z

1.use try {} catch{} block (reference java exception handling)

public class MySource extends DecimalFormat{ public static void main(String[] args) { int weight; int height; double bodyMassIndex; DecimalFormat dfWithTwoDecimalPlaces; Scanner scanner; scanner = new Scanner(System.in); while(true) { try { System.out.print("What is your weight in kilograms (kg): "); weight = scanner.nextInt(); System.out.print("What is your height in centimeters(cm): " ); height = scanner.nextInt(); break; }catch(InputMismatchException e) { System.out.println("Please enter a whole number."); scanner.nextLine(); } } bodyMassIndex = (weight / Math.pow(height/100.0, 2.0) ); dfWithTwoDecimalPlaces = new DecimalFormat ("0.00"); System.out.print("Your Body Mass Index is: " + dfWithTwoDecimalPlaces.format(bodyMassIndex)); }

}

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