JavaPrimesInput

import java.util.Scanner;


public class Primes {

    public static void main(String[] args) {
        // Start of the View
        int n = 10;
        Scanner input = new Scanner(System.in);

        System.out.print("I will calculate Primes up to n. Please, enter n: ");

        while(!input.hasNextInt()){
            String error = input.next();
            System.out.printf("\n %s is not a number. Please try again: ", error);
        }
        n = input.nextInt();
        input.close();
        // End of the view

        int prime = 1;
        for(int i = 0; i < n; i++) {
            prime = i;
            for(int j = 2; j < (int)Math.sqrt(i); j++) { // j < i
                if (i % j == 0) {
                    prime = 0;
                    break;
                }
            }
            if (prime != 0) System.out.println(i);
        }
    }

    public static boolean isPrime(int n)
    {
        boolean flag = true;
        for (int i = 2; i < (int)Math.sqrt(i); i++) {
            if (n % i == 0) {
                flag = false; // or retur false;
                break;
            }
        }
        return flag;
    }

}