Here is simple code for calculator so you can consider this import java.util.*; import java.util.Scanner; public class Hello { public static void main(String[] args) { System.out.println("Enter first and second number:"); Scanner inp= new Scanner(System.in); int num1,num2; num1 = inp.nextInt(); num2 = inp.nextInt(); int ans; System.out.println("Enter your selection: 1 for Addition, 2 for substraction 3 for Multiplication and 4 for division:"); int choose; choose = inp.nextInt(); switch (choose){ case 1: System.out.println(add( num1,num2)); break; case 2: System.out.println(sub( num1,num2)); break; case 3: System.out.println(mult( num1,num2)); break; case 4: System.out.println(div( num1,num2)); break; default: System.out.println("Illigal Operation"); } } public static int add(int x, int y) { int result = x + y; return result; } public static int sub(int x, int y) { int result = x-y; return result; } public static int mult(int x, int y) { int result = x*y; return result; } public static int div(int x, int y) { int result = x/y; return result; } }