code: public Integer getInteger (String key, Supplier<Integer> notFound) {
          return getParsed (key, Integer::new, notFound);
      }
docs: Retrieve a mapped element and return it as an Integer.
  
  @param key A string value used to index the element.
  @param notFound A function to create a new Integer if the requested key was not found
  @return The element as an Integer, or notFound if the element is not found.