div#div1:empty + div#div2 {display: none;}

<div id="div1"></div>
<div id="div2"></div>

public class LoopWithStep {
  int res = getSum(5, 10);
  public static int getSum(int n, int step) {
    int result = 0;

    for (int i = 0; i <= n;  i = i + step) {
      result += i;
    }

    return result;
  }
}