Calculaor Assisgnment

gistfile1.txt

package com.company.demo;

import java.util.Scanner;

public class Caculator1 {

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

        System.out.println("Enter First number: ");
        int a= scr.nextInt();

        System.out.println("Enter Second Number: ");
        int b= scr.nextInt();
//        int c= a+b;
        System.out.println(" The result of c :" + c);


        System.out.println("for Addition, enter 1, " + "for Subtraction, enter 2," + " for Multiplication, enter 3,"+ "for Division, enter 4");

        int res= scr.nextInt();

        if (res==1){

            int result= cal.add(a,b);
            System.out.println("result is " + result);
        }
        else if(res==2){
            int result= cal.sub(a,b);
            System.out.println("result is " + result);
        }

        else if(res==3){
            int result= cal.mult(a,b);
            System.out.println("result is " + result);
        }
        else if(res==4){
            int result= cal.div(a,b);
            System.out.println("result is " + result);
        }
//        long c = a + b;
//        System.out.println("Total number for c is :" + c);

    }
}

Hi,
Mine one is not working!!

add, sub, mult and div( all are red color).
can you please let me know why it's happening?
Thanks!
Kabir