Exception in thread "main" java.util.InputMismatchException nextDouble() error?

Question

CitireFisier.java

public class CitireFisier  {
    public static void main(String[] args) {
        File f = new File("fisier.txt");

        Scanner scn = null;
        try {
            scn = new Scanner(f);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        int size = scn.nextInt();  
        System.out.println("val  is " + size);

        double var  = scn.nextDouble();
        System.out.println("val  is " + var);
    }
}

Output

val is 3
Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)

fisier.txt

3
0.1 0.7 0.2 init g
0.0 0.0 1.0 g y
0.0 0.0 1.0 g y

nextDouble() receive the error but 0.1 is double!

score 2 · Accepted Answer · answered Mar 21 '16 at 11:56

2

If your locale uses comma as the decimal separator, then 0.1 is not a double.

To fix this, instantiate your Scanner like so:

 scn = new Scanner(f).useLocale(Locale.US);

answered Mar 21 '16 at 11:56

RafToTheK

86
4

Yes, this is a wise answer. French, German, and Italian uses a comma, and this will break when using those locales. – Mr. Polywhirl Mar 21 '16 at 11:59
Thanks! it works with scn = new Scanner(f).useLocale(Locale.US); – dany Mar 21 '16 at 12:03

score 0 · Answer 2 · edited May 23 '17 at 11:59

I guess the problems depends on the Java version used, because in my Java Version (Java(TM) SE Runtime Environment (build 1.8.0_74-b02)), I don't get the error. Nevertheless, maybe this helps for your version (as mentioned in the question's comments):

public static void main(String[] args) {
    File f = new File("fisier.txt");
    Scanner scn = null;
    try {
        scn = new Scanner(f);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    int size = scn.nextInt();
    System.out.println("val  is " + size);

    // not needed in my Java Version
    scn.nextLine();

    double var = scn.nextDouble();
    System.out.println("val  is " + var);
}

EDIT:

You may also want to look at Trouble using nextInt and nextLine()

Exception in thread "main" java.util.InputMismatchException nextDouble() error?

CitireFisier.java

Output

fisier.txt

2 Answers2