Basic Calculator

#1

import java.util.*;
import java.util.Scanner;
public class Main {
public static void main(String args[]) {
// Your Code Here
boolean flag=true;
do {
Scanner s=new Scanner(System.in);

	char n = s.next().charAt(0);
	
	switch(n) {
	case '+':
		int num1=s.nextInt();
		int num2=s.nextInt();
		System.out.println(num1+num2);
		break;
	case '-':
		num1=s.nextInt();
		num2=s.nextInt();
		System.out.println(num1-num2);
		break;
	case '*':
		num1=s.nextInt();
		num2=s.nextInt();
		System.out.println(num1*num2);
		break;
	case '/':
		num1=s.nextInt();
		num2=s.nextInt();
		System.out.println(num1/num2);
		break;
	case '%':
		num1=s.nextInt();
		num2=s.nextInt();
		System.out.println(num1%num2);
		break;
	case 'x':
		flag=false;
		break;
	case 'X':
		flag=false;
		break;
	default :{
		System.out.println("Invalid operation. Try again.");
		break;
	}

	}
	
}while(flag==true);

}

}

Error is :
Exception in thread “main” java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1371)
at Main.main(Main.java:9)

Why this error occur? How can I resolve it

#2

@ankitsharma11072002 bench mark your code with this code and you will see your mistake
and also don’t initialise your scanner inside the do while loop . initialise it outside the loop.

import java.util.Scanner;
public class main{
   static Scanner scn=new Scanner(System.in);
    public static void main(String[] args) {
        char ch;
        do {
            ch = scn.next().charAt(0);  // Use cin in case of c++
            if (ch == '+' || ch == '-' || ch == ' * ' || ch == '/' || ch == '%') {
                operation(ch);
            } else {
                if (ch != 'x' && ch != 'X')
                    System.out.println("Invalid operation. Try again.");
            }
        } while (ch != 'x' && ch != 'X');
    }
    public static void operation(char ch) {
        int a = scn.nextInt(); // Use cin in case of c++
        int b = scn.nextInt(); // Use cin in case of c++
        int res = 0;
        switch (ch) {
        case '+': {
            res = a + b;
            break;
        }
        case '-': {
            res = a - b;
            break;
        }
        case '*': {
            res = a * b;
            break;
        }
        case '/': {
            res = a / b;
            break;
        }
        case '%': {
            res = a % b;
            break;
        }
        }
        System.out.println(res);
    }
}
#3

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