Locale
class Locale(val language: String? = null, val country: String? = null, val variant: String? = null)
ported to keep API surface compatible with Java lucene However, as I ever know, only QueryParserBase and some class are using Locale for the purpose of generating RangeQuery and Locale is used to feed DateFormat to get date instance. This operation can be ignored as we can implement equivalent without using Locale.
Also, in initialization process, locale is set to be defaultLocale(), so in most cases no need to to change it.
If lucene use Locale more extensively in the future, we may need to implement Locale in detail.