Returns a three-letter abbreviation for this locale's country. If the country matches an ISO 3166-1 alpha-2 code, the corresponding ISO 3166-1 alpha-3 uppercase code is returned. If the locale doesn't specify a country, this will be the empty string.

The ISO 3166-1 codes can be found on-line.

Returns:  A three-letter abbreviation of this locale's country.

Exceptions:

MissingResourceException

Throws MissingResourceException if the three-letter country abbreviation is not available for this locale.