扫描器类没有此类元素异常

Question

I'm a newbie to code and I'm trying to make a program that tells the user the temperature and how long to cook beef roasts. I decided to use scanner and now I'm getting the no such element exception error. This is what my code looks like, and I can't tell what I'm doing wrong.

import java.util.Scanner;

public class Roasts {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        System.out.println("Which Roast are you cooking?  1. Chuck 2. Tenderloin 3. Rib 4. Sirloin 5. Tri-tip 6. Shoulder ");

        int numb=0;

        numb=input.nextInt();

        switch (numb) {

            case 1:
            System.out.println("300 degrees for 3 hours");
            break;
            case 2:
            System.out.println("350 degrees for 1 hour, then turn off heat and leave roast in oven for 1 additional hour");
            break;
            case 3:
            System.out.println("375 degrees for 1 hour, then turn off heat and leave roast in oven for an additional 2 hours");
            break;
            case 4:
            System.out.println("350 degrees for 45 mins to one hour");
            break;
            case 5:
            System.out.println("375 degrees for 45 mins");
            break;
            case 6:
            System.out.println("325 degrees for 4 hours");
            break;
            default:
            System.out.println("invalid number please choose 1-6");
        }
    }
}

Answer 1

When NoSuchElementException is thrown (from here ):

Thrown by various accessor methods to indicate that the element being requested does not exist.

When Scanner.nextInt() throws NoSuchElementException (from here ):

If the input is exhausted

I actually don't see that your program that is crafted in an improper way, but it can be the case that you are supplying input that is causing this problem.

Probably you should consider checking Scanner#hasNextInt() before invoking Scanner#nextInt() .

I'd also recommend you to first read javadocs of the classes that you are using to get better understanding of the behavior and make more sense of the errors/exceptions that you are getting as you are a beginner. HTH.

Answer 2

The possible reason for this (though seems strange in that particular situation) is that new line character is left in your scanner object. Try to rework your line:

numb=input.nextInt();

to:

numb = Integer.parseInt(input.nextLine());

Answer 3

I tried running your code and it seems to me that there is no problem with it at all. Perhaps there is something wrong with your IDE?