private long hashTheBooking(Booking booking) { String toHash = booking.getRoomName() + booking.getUserMail(); SimpleDateFormat ft = new SimpleDateFormat("HHddMMyyyy"); toHash += ft.format(booking.getDate()); toHash += ft.format(booking.getCreationDate()); toHash += booking.getSpectacle().getName(); toHash += booking.getTotalPrice(); return toHash.hashCode(); }