> using the syntax for exotic identifiers At the level of the JVM, the entire string #"@\"What a wonderful world!\"" is a valid 31 character package, class, method and field name including the #, the \ and the quotes. So that syntax doesn't help.
> appears that NUL, CR, and LF can't be part... Prime facie, CR and LF characters are valid in Java package and class names. To fully support the JVM Spec, the JVM Manifest processing classes should provide an escaping scheme to allow such characters. However, it cannot use the obvious '\' character because it too is allowed in Java package and class names.