AvalonMailRepository key generation

[Kwirirai]

 
 
Hi 
Could you help me in figuring out how the keys for storing mail in
AvalonMailRepository are implemented .I have tried to follow the source
code but to no avail.
What I really want to know is how are the keys generated in such a way
that duplicates do not occur even if the server is shut down.I am just
trying to get a better 
understanding of James storage.
 
Kwirirai Nhakwi
 
Harare, Zimbabwe