Period in output double but comma in input double?

Question

I wrote a simple calculator in java, which takes two numbers of type Double from the user and outputs the sum. When I i input the numbers with periods (2.0) I get errors. But when I input with a comma (2,0) it works! It then outputs the answer in the form of 2.0.

Why does my java recognize a double input by comma, but outputs it with a period? The video tutorial I followed, the guy input his double with periods and got it output with periods..

this is my code:

import java.util.Scanner;

public class ScannerIntro {
    public static void main(String args[]){

        Scanner bucky = new Scanner(System.in);
        double firstNumber, secondNumber, answer;
        System.out.println("Enter first number: ");
        firstNumber = bucky.nextDouble();

        System.out.println("Enter Second number: ");
        secondNumber = bucky.nextDouble();

        answer = firstNumber+secondNumber;
        System.out.println("The answer is:");
        System.out.println(firstNumber+" + "+secondNumber+" = "+answer);

    }
}

Answer 1

The way the input is interpreted by nextdouble (Class Scanner) depends on the locale you're at:

http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html

In some countries (like France or Germany, a period is used as thousands-separator while the comma is used as decimal Point.

The output is from a different class that uses the default way.

You could either

1) Set the locale for your Scanner so it matches the output. For this use the function:

  useLocale(Locale locale)

2) Set the format printf does Format your numbers:

From the docs: https://docs.oracle.com/javase/tutorial/java/data/numberformat.html

public PrintStream format(Locale l, String format, Object... args)

Both ways will work. Now you have to decide which is the preferred one for you.