Simple program not running , InputMismatchException

[Gourav Das]

Why is scanner throwing InputMismatchException at line 14 , i don't understand .

Please help

import java.util.Scanner;

class MonthConverter {
	
	public static void main(String[] args) {
		
		Scanner scan = new Scanner("System.in");
		
		
		int grade;
		
		
			System.out.println("Please enter a student grade: ");
			grade = scan.nextInt();

			System.out.println("You entered : " + grade);
			
	}
}

[Dave Tolls]

Because you have simply hit <return> without entering a number.

[Gourav Das]

Dave Tolls wrote:Because you have simply hit <return> without entering a number.

No you are wrong , java doesnt work like that , it will keep blinking as long as he user keeps pressing enter..

[Dave Tolls]

Nope.

From here:

Throws:
InputMismatchException - if the next token does not match the Integer regular expression, or is out of range

An empty String would class as not matching the Integer regex.

[Campbell Ritchie]

I would have thought an empty String would match the delimiter, which is multiple whitespace. Let's try the offending code. No, that isn't necessary. The error isn't where we thought it was. It is on line 6 7. Its baleful effects don't become evident until line 14.

Why are you calling the class MonthConverter? It doesn't convert any months to anything.
Don't declare variables earlier than you need them. Delete line 10, and get rid of some of the excess empty space. You now have this:-

import java.util.Scanner;
 
class MonthConverter {
    public static void main(String[] args) {
        Scanner scan = new Scanner("System.in");
        System.out.println("Please enter a student grade: ");
        int grade = scan.nextInt();
        System.out.println("You entered : " + grade);
    }
}

Look at line 7, which is a better way to declare the variable. But I haven't corrected the original problem.

[edit]Somebody told me I got the line number fr the error wrong: should be 7

[Junilu Lacar]

You're instantiating your Scanner with a string, "System.in", not the InputStream, System.in. Your call to nextInt() tries to parse the String into a number which obviously will fail since "System.in" does not have anything in it remotely parseable into an int, that's why you're getting the exception.

Basically, you're using the constructor Scanner(String source), not the one you actually wanted, Scanner(InputStream source)

[Abinn Gautam]

The following works:

public class MonthConverter {


    public static void main(String[] args) {
       // Scanner scan = new Scanner("System.in");
        Scanner scan = new Scanner(System.in);


        int grade;


        System.out.println("Please enter a student grade: ");
        grade = scan.nextInt();

        System.out.println("You entered : " + grade);


    }
}