There are two entries in the error text file, javac.properties for
the error javac.err.class.not.found.

gzilla% grep class.not.found javac.properties
javac.err.class.not.found=\\
javac.err.class.not.found=\\
gzilla%


Not a world shattering error, but a minor infelicity that may confuse an implementor
or error-language translator one of these days.