Calculate the sum of prime numbers

import java.io.*;
class PrimeNumber {
  public static void main(String[] args) throws Exception{
    int i ;
    BufferedReader bf = new BufferedReader(
              new InputStreamReader(System.in));
    System.out.println("Enter number:");
    int num = Integer.parseInt(bf.readLine());
  
    System.out.println("Prime number: ");
    for (i=1; i < num; i++ ){
      int j;
      for (j=2; j<i; j++){
        int n = i%j;
        if (n==0){
          break;
        }
      }
      if(i == j){
        System.out.print("  "+i);
      }
    }
  }
}