Check whether the given number is prime or not?

Question

I am trying to implement a code to check whether a given array of numbers is prime or not,

but when the number is not a prime number, the output displays "Prime" and "Not Prime" both answers. What is the mistake I did here and it is a pleasure to have an answer from you? Thank you in advance!

Here is my code.

    Scanner scan = new Scanner(System.in);
    int number = scan.nextInt();
    int[] arr = new int[number];
    for (int i = 0; i < number; i++) {
        arr[i] = scan.nextInt();

    }

    for (int i = 0; i < number; i++) {
        int num = arr[i];
        for (int j = 2; j <= Math.sqrt(num); j++) {
            if (num % j == 0 && num !=2) {
                System.out.println(num + "Not prime");
                break;
            }
        }
        System.out.println(num +"Prime");
    }

Answer 1

If you're interested in making your code a little more efficient you can go this route.

int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
        15, 16, 17, 18, 19, 20 };
for (int num : numbers) {
    System.out.println(num + ((isPrime(num) ? " is" : " is not") + " a prime"));
}       

private static boolean isPrime(int num) {
    // two is a prime
    if (num == 2) {
       return true;
    }
    // numbers 1 or less or any even 
    // number (sans 2) are not primes
    if (num <= 1 || num % 2 == 0) {
        return false;
    }
    // Now you can check for odd divisors.
    // and increment by 2 starting with 3.
    for (int i = 3; i <= Math.sqrt(num); i+=2) {
        if (num % i == 0) {
            return false;
        }
    }
    return true;
}