Resource bundles: properties files, naming and lookup/fallback order

A resource bundle keeps locale-specific data, mostly user interface text, outside your code so that translators can supply new languages without code changes. The most common form is a family of properties files that share a base name, with the locale appended: Messages.properties (the default), Messages_fr.properties, Messages_fr_CA.properties, Messages_en_US.properties. Java class bundles that extend ListResourceBundle are also possible and, for the same name, a class is preferred over a properties file.