Check if a number is prime in Java

public class PrimeNumber {
    public static void main(String[] args) {
        int num = 29;
        boolean isPrime = true;
        if (num <= 1) {
            isPrime = false;
        } else {
            for(int i = 2; i <= Math.sqrt(num); i++) {
                if (num % i == 0) {
                    isPrime = false;
                    break;
                }
            }
        }
        System.out.println(num + " is prime? " + isPrime);
    }
}