Java Program to Check Prime or Not

To check the entered number by user is prime or not have to know about the prime number.

Prime Number :- Prime Number is divisible by 1 or itself.

So in below program we check from 2 to the half of the number 
and divide it with integer i every iteration and count it division by counter c. If counter is c is then it is prime number otherwise number is not Prime.


Implementation :-

import java.util.Scanner;
class PrimeNum
{
    public static void main(String[] args)
    {
        System.out.println("Enter a number: ");
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        int c=0,i;
        for(i=2; i<=num/2; i++)
        {
            if(num%i==0)
            {
                c++;
                break;
            }       
        }
        if(c==0)
           {
               System.out.println(num+" is a prime number");
           }
        else
        {
             System.out.println(num+" is not a prime number");
        }
    }
}


 Output :-

D:\AllPrograms\1232>javac PrimeNum.java
D:\AllPrograms\1232>java PrimeNum
Enter a number:
13
13 is a prime number

D:\AllPrograms\1232>java PrimeNum
Enter a number:
11
11 is a prime number

D:\AllPrograms\1232>java PrimeNum
Enter a number:
5
5 is a prime number

D:\AllPrograms\1232>java PrimeNum
Enter a number:
12
12 is not a prime number