Java program to check if nubmer is a prime number

public class Main {

	public static void main(String[] args) {
		// Prime Number : the number which is divisible by 1 and itself.
		// 2,3,5,7,11,13...........etc.
		// 1 is not a prime number
		
		int num = 3;
		boolean flag = false;
		
		for(int i=2; i<=num/2; i++) {
			if(num % i == 0) {
				flag = true;
				break;
			} 
		}
		if(!flag) {
			System.out.println(num + " is a prime number");
		}
		else {
			System.out.println(num + " is not a prime number");
		}
	}

}