learn tricks in java jar file

I used java jar files for some years but didn't realize several interesting mechanisms inside of jar file. Now I have a chance of reading jar specification and found several very handy features:

-- specify class-path in MANIFEST.MF

-- create index files (INDEX.LIST) for all packages.

-- META-INF/services directory to associate an implementation with its definition (e.g. class to interface)

These all come handy for easy distribution of a package