Calculator Java Input

November 28, 2021

I’m trying to make a calculator in java that can multiply subtract and add depending if the user wants that they can choose what they want. For some reason its giving me a weird output
Code

import java.util.Scanner;  // Import the Scanner class

public class calculator {
    public static void main(String args[]){
        Scanner sc= new Scanner(System.in);
            //System.in is a standard input stream  
        System.out.print("Enter first number- ");  
        int a = sc.nextInt();  
        System.out.print("Enter second number- ");  
        int b = sc.nextInt();  
        System.out.print("Do you want to multiply, add, divide, or subtract? ");  
        String c = sc.nextLine();  
        switch(c) {
            case "multiply":
              System.out.print(a * b);
              break;
            case "add":
              System.out.print(a * b);
              break;
            default:
              System.out.print("Invalid input!");
        }


    }
    
}

Output

Enter first number- 2
Enter second number- 2
Do you want to multiply, add, divide, or subtract? Invalid input!

Like I didnt even type Invalid input it just does it by itself for some reason

>Solution :

sc.nextInt() does not read the enter key that you entered, so sc.nextLine() will read that new line and return it. Use sc.next() instead of sc.nextLine() to avoid this issue. Your code also multiplies the numbers when the user inputs add, so I changed that as well.

import java.util.Scanner;  // Import the Scanner class

public class calculator {
    public static void main(String args[]){
        Scanner sc= new Scanner(System.in);
        //System.in is a standard input stream  
        System.out.print("Enter first number- ");  
        int a = sc.nextInt();  
        System.out.print("Enter second number- ");  
        int b = sc.nextInt();  
        System.out.print("Do you want to multiply, add, divide, or subtract? ");  
        String c = sc.next();  
        switch(c) {
            case "multiply":
                System.out.print(a * b);
                break;
            case "add":
                System.out.print(a + b);
                break;
            default:
                System.out.print("Invalid input!");
        }
    }
}