code: public static boolean handleIfModifiedSince(final HttpServerExchange exchange, final Date lastModified) {
          return handleIfModifiedSince(exchange.getRequestHeaders().getFirst(Headers.IF_MODIFIED_SINCE), lastModified);
      }
docs: Handles the if-modified-since header. returns true if the request should proceed, false otherwise
  
  @param exchange     the exchange
  @param lastModified The last modified date
  @return