code: public String getFirstHeader(String name) {
          List<String> headerValues = getHeader(name);
  
          if (headerValues == null || headerValues.size() == 0) {
              return null;
          }
  
          return headerValues.get(0);
      }
docs: Get the first header value for the given header name, if it exists.
  
  @param name the name of the header to get
  @return the first value of the given header name