Tweak 'fat jar' handling to generally improve performance:
- Allow JarURLConnection to throw a static FileNotFoundException when
loading classes. This exception is thrown many times when attempting
to load a class and is silently swallowed so there is no point in
providing the entry name.
- Expose JarFile.getJarEntryData(AsciiBytes) and store AsciiBytes in
the JarURLConnection. Previously AsciiBytes were created, discarded
then created again.
- Use EMPTY_JAR_URL for the JarURLConnection super constructor. The URL
is never actually used so we can improve performance by using a
constant.
- Extract JarEntryName for possible caching. The jar entry name
extracted from the URL is now contained in an inner JarEntryName
class. This could be cached if necessary (although currently it is
not because no perceivable performance benefit was observed)
Fixes gh-1119
a3ceaf63e2