How to create error message when negative number is entered in Java factorial

Question

I need to modify this code so that and error message is displayed when a negative number is entered. I know and else statement has to fit in I just can figure out where.

Answer 1

I guess all you need to do is check for incorrect input to throw an exception.

public static void numberFactorial() {  
    System.out.println("Option 2 selected, enter a number: "); 
    int number = sc.nextInt(); 
    if(number < 0){
         throw new IllegalArgumentException()
    }
    // ... rest of the code
}