code: public void setFontSize(int header_font_size, int details_font_size) {
          this.headerLabel
                  .setStyle("-fx-font-size:" + Integer.toString(header_font_size) + "px;");
          this.detailsLabel
                  .setStyle("-fx-font-size:" + Integer.toString(details_font_size) + "px;");
      }
docs: Sets both font sizes in pixels for the header and the details label with
  two font sizes <code>integer</code> parameters given.
  
  @param header_font_size The header font size in pixels
  @param details_font_size The details font size in pixels