java.util.Properties
is like java.util.Hashtable
(legacy) but with very useful methods for saving to & loading from files. The class is widely used for configuration files.
A properties file is pure text comprising name/value pairs. The separator between name & value can be '=', ':' or a space. Comment lines begin '#' or '!'. Eg,
# My configuration file
file.menu=File
file.new=New
file.open=Open
# ...
Ie, labels for menus. These can then easily be swapped for versions in other languages (I18N = InternationalisatioN).
See also java.util.ResourceBundle
in the API documentation. Resource bundles are widely used for multi-lingual web sites.