java - Weird behaviour with Scanner#nextFloat

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Running the following in Eclipse
initially caused Scanner to not recognize carriage returns in the console effectively
blocking further input:

price =
            sc.nextFloat();

Adding
this line before the code causes Scanner to accept 0,23 (french notation) as a
float:

Locale.setDefault(Locale.US);

This
is most probably due to regional settings in Windows XP Pro (French/Belgian). When the
code is run again 0,23 is still accepted and entering 0.23 causes it to throw a
java.util.InputMismatchException.

Any
explanation as to why this is happening? Also is there a workaround or should I just use
Float#parseFloat?

Edit:
This demonstrates how Scanner behaves with different Locales (uncomment one of the lines
at the
beginning).

import
            java.util.Locale;
import
            java.util.Scanner;


public class NexFloatTest
            {

 public static void main(String[] args) {


            //Locale.setDefault(Locale.US);

            //Locale.setDefault(Locale.FRANCE);


 // Gives fr_BE on
            this system
 System.out.println(Locale.getDefault());


            float price;

 String uSDecimal = "0.23";
 String
            frenchDecimal = "0,23";

 Scanner sc = new
            Scanner(uSDecimal);


 try{
 price =
            sc.nextFloat();
 System.out.println(price);
 } catch
            (java.util.InputMismatchException e){
 e.printStackTrace();

            }

 try{
 sc = new
            Scanner(frenchDecimal);

 price = sc.nextFloat();

            System.out.println(price);
 } catch (java.util.InputMismatchException
            e){
 e.printStackTrace();
 }


            System.out.println("Switching Scanner to System.in");


            try{
 sc = new Scanner(System.in);


            System.out.println("Enter a float value");
 price = sc.nextFloat();

            System.out.println(price);
 } catch (java.util.InputMismatchException
            e){
 e.printStackTrace();
 }


            System.out.print("Enter title:");

 String title = sc.nextLine(); //
            This line is skipped



            System.out.print(title);

            }

}

Edit:
This reproduces the issue where the Scanner is waiting for a float value but fails to
trigger when you press
return:

import
            java.util.Scanner;


public class IgnoreCRTest
            {

 public static void main(String[] args) {
 Scanner sc =
            new Scanner(System.in);
 System.out.println("Enter a float
            value:");
 // On french Locale use , as the decimal separator
 float
            testFloat = sc.nextFloat();
 System.out.println(testFloat);

            //sc.skip("\n"); // This doesn't solve the issue


            sc.nextLine();
 System.out.println("Enter an integer value:");
 int
            testInt = sc.nextInt();
 System.out.println(testInt);
 // Will
            either block or skip here
 System.out.println("Enter a string value
            :");
 String testString = sc.nextLine();

            System.out.println(testString);

            }


}

Answer

I wonder if you're not handling an end of
line token appropriately. Often if you use Scanner#next###() (except for nextLine), and
you reach an end of line token as when the user presses enter, if you don't handle the
end of line token, it will prevent the Scanner object from working appropriately. To
solve this, call Scanner#nextLine() when this token needs to be handled. If you post
some of your code, we can see if this indeed is your problem and if my suggestion offers
a solution.

edit: nope, you're not using
System.in so this is not the problem. On the other hand, you do need to set the locale
of the Scanner before accepting the French number.
i.e.,

 sc = new
            Scanner(frenchDecimal);
 sc.useLocale(Locale.FRENCH);
 price =
            sc.nextFloat();