problem with Java's Scanner: InputMismatchException

Question

I have this code:

import java.util.Scanner;

public class Maggiore3Valori {
    public static void main(String[] args) {
        Scanner scanner = new Scanner("System.in");

        int num1, num2, num3;
        int max;

        System.out.println("Inserisci il primo numero: ");
        num1 = scanner.nextInt();

        System.out.println("Inserisci il secondo numero: ");
        num2 = scanner.nextInt();

        System.out.println("Inserisci il terzo numero: ");
        num3 = scanner.nextInt();

        if (num1 > num2 && num1 > num3) {
            max = num1;
        } else if (num2 > num1 && num2 > num3) {
            max = num2;
        } else {
            max = num3;
        }

        System.out.println("Il maggiora trai tre è: " + max);
        scanner.close();
    }
}

When I run it, before I can input the first number the console gives me this error:

Inserisci il primo numero:
Exception in thread "main" java.util.InputMismatchException
    at java.base/java.util.Scanner.throwFor(Scanner.java:939)
    at java.base/java.util.Scanner.next(Scanner.java:1594)
    at java.base/java.util.Scanner.nextInt(Scanner.java:2258)
    at java.base/java.util.Scanner.nextInt(Scanner.java:2212)
    at Maggiore3Valori.main(Maggiore3Valori.java:13)

I read around that the problem is with the type of variables; but they should be right. What does this error mean? How can I solve it?

Do you mean `"System.in"` (a file with that name), or do you really mean `System.in` (the standard input stream)? — Andy Turner, Jan 28 '20 at 11:02

score 5 · Accepted Answer · answered Jan 28 '20 at 11:04

Scanner scanner = new Scanner ("System.in");

This creates a scanner that reads a file in the current directory named System.in.

That's probably not what you mean. To read from the standard input, remove the quotes:

Scanner scanner = new Scanner (System.in);

score 2 · Answer 2 · answered Jan 28 '20 at 11:09

2

Replace,

Scanner scanner = new Scanner ("System.in");

with

Scanner scanner = new Scanner (System.in);

answered Jan 28 '20 at 11:09

KAMLESH KUMAR

130
7

score 0 · Answer 3 · answered Jan 28 '20 at 11:05

Just remove the double quote from System.in and you are good to go.

import java.util.Scanner;
public class Maggiore3Valori {

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

         int num1, num2, num3;
         int max;

         System.out.println ("Inserisci il primo numero: ");
         num1 = scanner.nextInt();

         System.out.println ("Inserisci il secondo numero: ");
         num2 = scanner.nextInt();

         System.out.println ("Inserisci il terzo numero: ");
         num3 = scanner.nextInt();

         if (num1 > num2 && num1 > num3) {
             max = num1;
         }
         else if (num2 > num1 && num2 > num3) {
             max = num2;
         }
         else {
             max = num3;
         }

         System.out.println ("Il maggiora trai tre è: " + max);

        scanner.close();

    }

}

problem with Java's Scanner: InputMismatchException

3 Answers3