Locale
A locale is a set of parameters that defines the user's language and country. Several date functions can be configured by a locale, given by an identifier as a "String" parameter. An identifier of a locale always contains an ISO Language Code. Optionally, an ISO Country Code can follow after an underscore.
Examples
de_DE = German/Germany, Language de, Country DE
de_AT = German/Austria, Language de, Country AT
Further information
http://en.wikipedia.org/wiki/Locale#Java
http://docs.oracle.com/javase/7/docs/api/java/util/Locale.html