java.util.prefs.FileSystemPreferencesFactory exclusively

not OS-related preference factories (such as Windows registry)

ClassLoader set to first try to load a file from its own class if the
given path includes that class name

lambda expressions   val -> val.getEnd()
lambda methods       System.out::println

will use a singleton class instance (unlike Java) if no final references
are involved.

now shows output directory, from .j2s#j2s.site.directory