ProgBasics07Nested-Loops-Y07sumPrimeNonPrime2

import java.util.Scanner;

public class Y07sumPrimeNonPrime2 {
        public static void main(String[] args) {
            Scanner scanner = new Scanner(System.in);
            long sumPrimeNumbers = 0;
            long sumNonPrimeNumbers = 0;

            String input = scanner.nextLine();
            while (!input.equals("stop")) {

                int number = Integer.parseInt(input);
                if (number < 0) {
                    System.out.println("Number is negative.");
                } else {
                    if (isPrime(number)) {
                        sumPrimeNumbers += number;
                    } else {
                        sumNonPrimeNumbers += number;
                    }
                }
                input = scanner.nextLine();
            }
            System.out.println("Sum of all prime numbers is: " + sumPrimeNumbers);
            System.out.println("Sum of all non prime numbers is: " + sumNonPrimeNumbers);
        }

        private static boolean isPrime(int num) {
            boolean isPrime = true;
            if (num < 2) isPrime = false;
            else {
                for (int i = 2; i <= Math.sqrt(num); i++) {
                    if (num % i == 0) {
                        isPrime = false;
                        break;
                    }
                }
            }
            return isPrime;
        }
    }