how to write in java prime numbers code example

Example 1: prime number program in java

public class Prime {
    public static void main(String[] args) {

        int num = 29;
        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.");
}}

Example 2: primenumbers java

It will display the prime numbers between 1 and 100.

class PrimeNumbers
{
   public static void main (String[] args)
   {		
       int i =0;
       int num =0;
       //Empty String
       String  primeNumbers = "";

       for (i = 1; i <= 100; i++)         
       { 		  	  
          int counter=0; 	  
          for(num =i; num>=1; num--)
	  {
             if(i%num==0)
	     {
 		counter = counter + 1;
	     }
	  }
	  if (counter ==2)
	  {
	     //Appended the Prime number to the String
	     primeNumbers = primeNumbers + i + " ";
	  }	
       }	
       System.out.println("Prime numbers from 1 to 100 are :");
       System.out.println(primeNumbers);
   }
}