They were http and just returned a redirection header. Now use
https-URLs

added System.out.println to give user feedback about starting; Request user to enter text for echoing

added calculation of download duration; only show the first 300 chars of content, because made download files big. so showing everything would crash eclipse

fixed links to books; fixed formatting; added hints for starvation, livelock; removed volatile in example codes for thread safe x++,x--

ExecutorService and Callable

moved initFlightsFromLoop to ctor of class ReservationSystem