A non-existent file has to be able to have a canonical path.
java.io.File is only an abstract representation of a file name (or
directory name) regardless of whether the file exists or not.  It's
nothing but a holder for the reprepresentation of the path to a file
system object.

I'm guessing the bit of verbage surrounding canonical forms of existing
and non-existent paths has to do with OS-dependant features, probably
specifically case sensitivity on Win32.

On UNIX
/home/joeuser/MyFile
and
/usr/joeuser/myFile

are distinct and can co-exist without collisions

The same isn't true of a similar situation on Win32.

For example:

Say on Windows you have a non-existent file (or more appropriately
don't have)

String canonical = (new File ( "/tmp/NonExistent.txt"
)).getCanonicalPath();

On Windows, if the file didn't exist, would return something like
"C:\tmp\NonExistent.txt"

Say you then created that file but with case like "nonExistent.txt"

Runing the -exact- same bit of code above (no change in case on the
constructor) would result in a canonical representation of:

"C:\tmp\nonExistent.txt"