code: public void setElement(String title, String subtitle, String quantity, String price, String currency, String image_url)
      {
          HashMap<String, String> element = new HashMap<String, String>();
          element.put("title", title);
          element.put("subtitle", subtitle);
          element.put("quantity", quantity);
          element.put("price", price);
          element.put("currency", currency);
          element.put("image_url", image_url);
          this.elements.add(element);
      }
docs: Set Element
  
  @param title the receipt element title
  @param subtitle the receipt element subtitle
  @param quantity the receipt element quantity
  @param price the receipt element price
  @param currency the receipt element currency
  @param image_url the receipt element image url