how to check if number prime in java

1public class Prime {
2    public static void main(String[] args) {
3
4        int num = 29;
5        boolean flag = false;
6        for(int i = 2; i <= num/2; ++i){
7            if(num % i == 0){
8                flag = true;
9                break;
10            }
11        }
12
13        if (!flag)
14            System.out.println(num + " is a prime number.");
15        else
16            System.out.println(num + " is not a prime number.");
17}}
18Source:www.progra
19

1public class Prime {
2
3    public static void main(String[] args) {
4
5        int num = 29;
6        boolean flag = false;
7        for(int i = 2; i <= num/2; ++i)
8        {
9            // condition for nonprime number
10            if(num % i == 0)
11            {
12                flag = true;
13                break;
14            }
15        }
16
17        if (!flag)
18            System.out.println(num + " is a prime number.");
19        else
20            System.out.println(num + " is not a prime number.");
21    }
22}

1public class PrimeNumberInJava
2{
3   public static void main(String[] args)
4   {
5      int a, b = 0, flag = 0;
6      int number = 17;
7      b = number / 2;
8      if(number == 0 || number == 1)
9      {
10         System.out.println(number + " is not prime number");
11      }
12      else
13      {
14         for(a = 2; a <= b; a++)
15         {
16            if(number % a == 0)
17            {
18               System.out.println(number + " is not prime number.");
19               flag = 1;
20               break;
21            }
22         }
23         if(flag == 0)
24         {
25            System.out.println(number + " is prime number.");
26         }
27      }
28   }
29}