java program to find prime number between 1 and 100

1class PrimeNumbers
2{
3   public static void main (String[] args)
4   {		
5       int i =0;
6       int num =0;
7       //Empty String
8       String  primeNumbers = "";
9
10       for (i = 1; i <= 100; i++)         
11       { 		  	  
12          int counter=0; 	  
13          for(num =i; num>=1; num--)
14	  {
15             if(i%num==0)
16	     {
17 		counter = counter + 1;
18	     }
19	  }
20	  if (counter ==2)
21	  {
22	     //Appended the Prime number to the String
23	     primeNumbers = primeNumbers + i + " ";
24	  }	
25       }	
26       System.out.println("Prime numbers from 1 to 100 are :");
27       System.out.println(primeNumbers);
28   }
29}