First of all, i am not English speaker. I might make many miskates in wirting. sorry.
secondly, I am reading your great book and analysing code in db package.
It is bit hard to understand cleary beause of my lack of ability of english and java skill.
my question is that
In your book, DvdFileAccess is degined as singlton. when it created, getDvdlist(true) is called to store all Dvd data in List<DVD>.
and persisteDvd method is called when addDvd and modifyDvd is called.
In persistedDvd method, Is .db file changed? or is List<DVD> changed? or both.
If my program stored all Dvd data in List<DVD> and I changed data in that, when should i change the .db file? (i.e when server is down or as soon as possible when data is changed)