comefrom: <awangdev>204. Count Primes_2.java
code: public boolean isPrime(int num) {
          if (num <= 1) return false;
          for (int i = 2; i * i <= num; i++) {
              if (num % i == 0) {
                  return false;
              }
          }
          return true;
      }
masked: public boolean var_0 ( int var_1 ) {
    if ( var_1 <= 1 ) return false ;
    for ( int var_2 = 2 ;
    var_2 * var_2 <= var_1 ;
    var_2 ++ ) {
      if ( var_1 % var_2 == 0 ) {
        return false ;
      }
    }
    return true ;
  }
  