Creating a calculator that calls the methods from a separate class using scanner

I'm creating a calculator where each of the calculator's functions have to be in a separate class and called from the main method using scanner input.

1.Add

2.Subtract

3.Multiplication

4.Division

5.Square

6.Power

7.Mod operation

8.Factorial

0.Quit

I must create each method called by an object. The calculator requires one main class (has main () method) and one user defined class which has above calculating methods. The program must let the user choose an operation (one of above calculations) and operand(s) (numbers). Some calculations require two operands. (e.g. A + B, AB) Some calculations require one operand. (e.g. A2, N!) Additional functions:

•Let the calculation function continues until user wants to exit this program.

•When one calculation is done, let user choose another operation.

•This program terminates when user selects END option.

•Implement all operations. Do not use Java library math methods.

I have the code for a program that is using switch statement and case, but our class hasn't even learned any of that. I have looked everywhere online for the past two days and just can't figure it out, so apologies if the solution is simple, and thank you to all help in advance. Here is the code to my program so far.

public static void main(String[] args) {
	 
	Scanner s = new Scanner(System.in);
	int choice;
	do
	{
		System.out.println("[1] Add ");
		System.out.println("[2] Subtract ");
		System.out.println("[3] Multiply ");
		System.out.println("[4] Division ");
		System.out.println("[5] Square ");
		System.out.println("[6] Power ");
		System.out.println("[7] Mod Operation ");
		System.out.println("[8] Factorial ");

		System.out.println("[0] Quit ");

		System.out.println("Please enter your choice: ");		
		choice = s.nextInt();
		int num1, num2;
		
		switch(choice)
		{
			case 1 : System.out.println("Enter two numbers to add: ");
				 num1 = s.nextInt();
				 num2 = s.nextInt();
				 System.out.println("The sum of " + num1 + " and " + num2 + 
						 " is: " + add(num1, num2));
				 break;

			case 2 : System.out.println("Enter two numbers to subtract: ");
				 num1 = s.nextInt();
				 num2 = s.nextInt();
				 System.out.println("The difference of " + num1 + " and " + num2 + 
						 " is: " + diff(num1, num2));
				 break;

			case 3 : System.out.println("Enter two numbers to multiply: ");
				 num1 = s.nextInt();
				 num2 = s.nextInt();
				 System.out.println("The product of " + num1 + " and " + num2 + 
						 " is: " + prod(num1, num2));
				 break;

			case 4 : System.out.println("Enter two numbers to divide: ");
				 num1 = s.nextInt();
				 num2 = s.nextInt();
				 System.out.println("The quotient of " + num1 + " and " + num2 + 
						 " is: " + quo(num1, num2));
				 break;

			case 5 : System.out.println("A number to square: ");
				 num1 = s.nextInt();
				 System.out.println("The square of " + num1 + " is: " + square(num1));
				 break;

			case 6 : System.out.println("Enter the base and the exponent: ");
				 num1 = s.nextInt();
				 num2 = s.nextInt();
				 System.out.println("The power of " + num1 + " to the " + num2 + 
						 "th power is: " + power(num1, num2));
				 break;

			case 7 : System.out.println("Enter two numbers to get the interger remainder of (modulo): ");
				 num1 = s.nextInt();
				 num2 = s.nextInt();
				 System.out.println("The modulo of " + num1 + " and " + num2 + 
						 " is: " + mod(num1, num2));
				 break;
		
			case 8 : System.out.println("Enter a number to get the factorial of: ");
				 num1 = s.nextInt();
				 System.out.println("The factorial of " + num1 + " is: " + factorial(num1));
				 break;
		
			case 0: System.out.println("Thank you for using my program...good bye!");
				System.exit(0);
		}
	}
	while(choice != 0);
	s.close();
}


public static int add(int num1, int num2)
{
	return num1 + num2;
}

public static int diff(int num1, int num2)
{
	return num1 - num2;
}

public static int prod(int num1, int num2)
{
	return num1 * num2;
}

public static double quo(int num1, int num2)
{
	return (double)num1 / num2;
}

public static int mod(int num1, int num2)
{
	return num1 % num2;
}

public static long power(int base, int exp)
{
        long result = 1;

    	while (exp != 0)
    	{
        		result *= base;
        		--exp;
    	}
	return result;
}

public static int square(int num)
{
	return num * num;
}

public static int factorial(int base)
{
	if (base == 0)    
			return 1;    
	else    
			return(base * factorial(base - 1));     
}

}

you can use a separate class called Functions with static methods

public class Functions{
    public static int add(int num1, int num2)
    {
        return num1 + num2;
    }
    
    public static int diff(int num1, int num2)
    {
        return num1 - num2;
    }
    
    public static int prod(int num1, int num2)
    {
        return num1 * num2;
    }
    
    public static double quo(int num1, int num2)
    {
        return (double)num1 / num2;
    }
    
    public static int mod(int num1, int num2)
    {
        return num1 % num2;
    }
    
    public static long power(int base, int exp)
    {
            long result = 1;
    
            while (exp != 0)
            {
                    result *= base;
                    --exp;
            }
        return result;
    }
    
    public static int square(int num)
    {
        return num * num;
    }
    
    public static int factorial(int base)
    {
        if (base == 0)    
                return 1;    
        else    
                return(base * factorial(base - 1));     
    }
}

and you call these methods Functions.add(num1, num2))

I'm not sure if that what you want

Here is an approach, which may be useful to you. I have done implementation for Addition and Subtraction, you can follow the same thing for other operations as well. You may want to have abstract class for single operand operations as well.

import java.util.Scanner;
public class Calculator {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int choice;
do {
System.out.println("[1] Add ");
System.out.println("[2] Subtract ");
System.out.println("[3] Multiply ");
System.out.println("[4] Division ");
System.out.println("[5] Square ");
System.out.println("[6] Power ");
System.out.println("[7] Mod Operation ");
System.out.println("[8] Factorial ");
System.out.println("[0] Quit ");
System.out.println("Please enter your choice: ");
choice = s.nextInt();
int num1, num2;
switch (choice) {
case 1:
Addition addition = new Addition(s);
addition.performOperation();
break;
case 2:
Subtraction subtraction = new Subtraction(s);
subtraction.performOperation();
break;
case 3:
System.out.println("Enter two numbers to multiply: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The product of " + num1 + " and " + num2 +
" is: " + prod(num1, num2));
break;
case 4:
System.out.println("Enter two numbers to divide: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The quotient of " + num1 + " and " + num2 +
" is: " + quo(num1, num2));
break;
case 5:
System.out.println("A number to square: ");
num1 = s.nextInt();
System.out.println("The square of " + num1 + " is: " + square(num1));
break;
case 6:
System.out.println("Enter the base and the exponent: ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The power of " + num1 + " to the " + num2 +
"th power is: " + power(num1, num2));
break;
case 7:
System.out.println("Enter two numbers to get the interger remainder of (modulo): ");
num1 = s.nextInt();
num2 = s.nextInt();
System.out.println("The modulo of " + num1 + " and " + num2 +
" is: " + mod(num1, num2));
break;
case 8:
System.out.println("Enter a number to get the factorial of: ");
num1 = s.nextInt();
System.out.println("The factorial of " + num1 + " is: " + factorial(num1));
break;
default:
System.out.println("Your choices should be 0 to 8!");
break;
}
}
while (choice != 0);
s.close();
System.out.println("Thank you for using my program...good bye!");
System.exit(0);
}
public static int prod(int num1, int num2) {
return num1 * num2;
}
public static double quo(int num1, int num2) {
return (double) num1 / num2;
}
public static int mod(int num1, int num2) {
return num1 % num2;
}
public static long power(int base, int exp) {
long result = 1;
while (exp != 0) {
result *= base;
--exp;
}
return result;
}
public static int square(int num) {
return num * num;
}
public static int factorial(int base) {
if (base == 0)
return 1;
else
return (base * factorial(base - 1));
}
}
abstract class OperationWithTwoOperands {
protected String prompt;
private Scanner scanner;
public OperationWithTwoOperands(Scanner scanner) {
this.scanner = scanner;
}
public void performOperation() {
System.out.println(prompt);
int num1 = scanner.nextInt();
int num2 = scanner.nextInt();
operation(num1, num2);
}
abstract protected void operation(int operand1, int operand2);
}
class Addition extends OperationWithTwoOperands {
public Addition(Scanner scanner) {
super(scanner);
prompt = "Enter two numbers to add:";
}
@Override
protected void operation(int num1, int num2) {
System.out.println("The sum of " + num1 + " and " + num2 + " is: " + (num1 + num2));
}
}
class Subtraction extends OperationWithTwoOperands {
public Subtraction(Scanner scanner) {
super(scanner);
prompt = "Enter two numbers to subtract:";
}
@Override
protected void operation(int num1, int num2) {
System.out.println("The difference of " + num1 + " and " + num2 + " is: " + (num1 - num2));
}
}