Criba de eratóstenes

import java.util.Arrays;
import java.util.Scanner;

public class Cribe {
    static int maxN = (int) 1e7;
    static boolean cribe[] = new boolean[maxN];
    static Scanner scanner = new Scanner(System.in);

    static void initCribe()
    {
        Arrays.fill(cribe, true);
        cribe[0] = (cribe[1] = false);
        for(int i = 2; i*i < maxN; i++)
        {
            if(cribe[i])
            {
                for(int j = i*i; j < maxN; j+=i)
                {
                    cribe[j] = false;
                }
            }
        }

    }

    static int forceReadPositiveInt(String message)
    {
        int n = 0;
        while(true)
        {
            try
            {
                System.out.println(message);
                n = Integer.parseInt(scanner.next());
                if(n > -1 ) return n;
                System.out.println("El número a testear debe ser mayor o igual a 0:.");
                continue;
            }
            catch(Exception ex)
            {
                System.out.println("Se introdujo un número inválido, reintente.");
            }
        }
    }

    public static void main(String[] args) {
        initCribe();
        while(true)
        {
            int x = forceReadPositiveInt("Ingrese número a testear:");
            System.out.println(cribe[x] ? "Es primo" : "No es primo");
            System.out.println("¿Continuará con los tests? (S/N)");
            if(scanner.next().charAt(0) == 'N') break;
        }

    }

}