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ResourceBundle is a set of related
subclasses that share the same base name. The list that follows shows a
set of related subclasses. ButtonLabel is the base name.
The characters following the base name indicate the language code,
country code, and variant of a Locale.
ButtonLabel_en_GB, for example, matches the
Locale specified by the language code for English
(en) and the country code for Great Britain
(GB).
ButtonLabel ButtonLabel_de ButtonLabel_en_GB ButtonLabel_fr_CA_UNIX
To select the appropriate ResourceBundle, invoke the
ResourceBundle.getBundle method. The following example
selects the ButtonLabel ResourceBundle for
the Locale that matches the French language, the country
of Canada, and the UNIX platform.
Locale currentLocale = new Locale("fr", "CA", "UNIX");
ResourceBundle introLabels =
ResourceBundle.getBundle("ButtonLabel", currentLocale);
If a ResourceBundle class for the specified
Locale does not exist, getBundle tries to
find the closest match. For example, if
ButtonLabel_fr_CA_UNIX is the desired class and the
default Locale is en_US,
getBundle will look for classes in the following order:
ButtonLabel_fr_CA_UNIX ButtonLabel_fr_CA ButtonLabel_fr ButtonLabel_en_US ButtonLabel_en ButtonLabel
Note that getBundle looks for classes based on the default
Locale before it selects the base class
(ButtonLabel). If getBundle fails to find a
match in the preceding list of classes, it throws a
MissingResourceException. To avoid throwing this
exception, you should always provide a base class with no suffixes.
ResourceBundle has two subclasses:
PropertyResourceBundle and
ListResourceBundle.
A PropertyResourceBundle is backed by a properties file. A
properties file is a plain-text file that contains translatable text.
Properties files are not part of the Java source code, and they can
contain values for String objects only. If you need to
store other types of objects, use a ListResourceBundle
instead. The section
Backing a ResourceBundle with Properties Files
shows you how to use a PropertyResourceBundle.
The ListResourceBundle class manages resources with a
convenient list. Each ListResourceBundle is backed by a
class file. You can store any locale-specific object in a
ListResourceBundle. To add support for an additional
Locale, you create another source file and compile it into
a class file. The section
Using a ListResource Bundle
has a coding example you may find helpful.
The ResourceBundle class is flexible. If you first put
your locale-specific String objects in a
PropertyResourceBundle and then later decided to use
ListResourceBundle instead, there is no impact on your
code. For example, the following call to getBundle will
retrieve a ResourceBundle for the appropriate
Locale, whether ButtonLabel is backed up by a
class or by a properties file:
ResourceBundle introLabels =
ResourceBundle.getBundle("ButtonLabel", currentLocale);
ResourceBundle objects contain an array of key-value
pairs. You specify the key, which must be a String, when
you want to retrieve the value from the ResourceBundle.
The value is the locale-specific object. The keys in the following
example are the OkKey and CancelKey strings:
class ButtonLabel_en extends ListResourceBundle {
// English version
public Object[][] getContents() {
return contents;
}
static final Object[][] contents = {
{"OkKey", "OK"},
{"CancelKey", "Cancel"},
};
}
To retrieve the OK String from the
ResourceBundle, you would specify the appropriate key when
invoking getString:
String okLabel = ButtonLabel.getString("OkKey");
A properties file contains key-value pairs. The key is on the left side
of the equal sign, and the value is on the right. Each pair is on a
separate line. The values may represent String objects
only. The following example shows the contents of a properties file
named ButtonLabel.properties:
OkKey = OK CancelKey = Cancel
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