Why reference: scheme is supported only for file URLs?

[Sahoo]

Hi,

I see the following code in BundleArchive.java:
           // Check if the location string represents a reference URL.
           if ((location != null) && 
location.startsWith(REFERENCE_PROTOCOL))
           {
               // Reference URLs only support the file protocol.
               location = location.substring(REFERENCE_PROTOCOL.length());
               if (!location.startsWith(FILE_PROTOCOL))
               {
                   throw new IOException("Reference URLs can only be 
files: " + location);
               }
            ...
Why does reference: scheme only work if the underlying URL represents a 
file? Can't the code assume that for all other protocols, the underlying 
stream is a JarInputStream and proceed from there?

Thanks,
Sahoo