The contents of the archives swing.jar, swing.zip
and swing.tar.gz are the same.

Some versions of Netscape Navigator try to use the
swing.jar file for a "Smart Update," so if you
encounter this and the accompanying error message,
please download the swing.zip or swing.tar.gz file.

You can use jar to unpack swing.zip, as is, or you
can rename the file to javathreads.jar first.