WatchService questions

[Alan Bateman]

Sebastian Sickelmann wrote:
> :
> So a user of the WatchService-API cannot count in the order of the events. 
The sequence of events needs to keep the user's view of the directory 
consistent. This implies an ordering for at least the create and delete 
events (irrespective of implementation). Your mails do raise the 
question on if modification events need to be ordered. Clearly there are 
cases where they should be ordered with respect to other event kinds. If 
a file is modified after it is created then you should expect the 
modification event after the create event. There are other examples like 
this. If several files are modified at around the same time then the 
ordering may or may not be useful but clearly cannot be guaranteed 
everywhere. Where it is important then the user can examine the file's 
modification time if that helps. So I think you have a worthy point and 
we should think about this case further to see if we should change the 
implementation. If it is changed then there are several possible 
approaches - for example modification events could be merged towards the 
head if the pending list reaches its limit. Alternatively modification 
events could initially be stored in a map (for fast lookup) and only 
added to the pending list when an event of a different kind needs to be 
queued (or the user retrieves the pending events).

-Alan.