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## java.util
Class ResourceBundle

    java.lang.Object
      |
      +--java.util.ResourceBundle

Direct Known Subclasses:
  DateFormatZoneData, ListResourceBundle, PropertyResourceBundle

public abstract class ResourceBundle
extends Object

Resource bundles contain locale-specific objects. When your program needs a locale-specific resource, a `String` for example, your program can load it from the resource bundle that is appropriate for the current user's locale. In this way, you can write program code that is largely independent of the user's locale isolating most, if not all, of the locale-specific information in resource bundles.

This allows you to write programs that can:

- be easily localized, or translated, into different languages
- handle multiple locales at once
- be easily modified later to support even more locales

One resource bundle is, conceptually, a set of related classes that inherit from `ResourceBundle`. Each related subclass of `ResourceBundle` has the same base name plus an additional component that identifies its locale. For example, suppose your resource bundle is named `MyResources`. The first class you are likely to write is the default resource bundle which simply has the same name as its family--`MyResources`. You can also provide as many related locale-specific classes as you need: for example, perhaps you would provide a German one named `MyResources_de`.

Each related subclass of `ResourceBundle` contains the same items, but the items have been translated for the locale represented by that `ResourceBundle` subclass. For example, both `MyResources` and `MyResources_de` may have a `String` that's used on a button for canceling operations. In `MyResources` the `String` may contain `Cancel` and in `MyResources_de` it may contain `Abbrechen`.

If there are different resources for different countries, you can make specializations: for example, `MyResources_de_CH` is the German language (de) in Switzerland (CH). If you want to only modify some of the resources in the specialization, you can do so.

When your program needs a locale-specific object, it loads the `ResourceBundle` class using the `getBundle` method:

>      ResourceBundle myResources =
>           ResourceBundle.getBundle("MyResources", currentLocale);

The first argument specifies the family name of the resource bundle that contains the object in question. The second argument indicates the desired locale. `getBundle` uses these two arguments to construct the name of the `ResourceBundle` subclass it should load as follows.

The resource bundle lookup searches for classes with various suffixes on the basis of (1) the desired locale and (2) the current default locale as returned by Locale.getDefault(), and (3) the root resource bundle (baseclass), in the following order from lower-level (more specific) to parent-level (less specific):

baseclass + "_" + language1 + "_" + country1 + "_" + variant1
baseclass + "_" + language1 + "_" + country1 + "_" + variant1 + ".properties"
baseclass + "_" + language1 + "_" + country1
baseclass + "_" + language1 + "_" + country1 + ".properties"
baseclass + "_" + language1
baseclass + "_" + language1 + ".properties"
baseclass + "_" + language2 + "_" + country2 + "_" + variant2
baseclass + "_" + language2 + "_" + country2 + "_" + variant2 + ".properties"
baseclass + "_" + language2 + "_" + country2
baseclass + "_" + language2 + "_" + country2 + ".properties"
baseclass + "_" + language2
baseclass + "_" + language2 + ".properties"
baseclass
baseclass + ".properties"

For example, if the current default locale is `en_US`, the locale the caller is interested in is `fr_CH`, and the resource bundle name is `MyResources`, resource bundle lookup will search for the following classes, in order:
`MyResources_fr_CH
MyResources_fr
MyResources_en_US
MyResources_en
MyResources`

The result of the lookup is a class, but that class may be backed by a properties file on disk. That is, if getBundle does not find a class of a given name, it appends ".properties" to the class name and searches for a properties file of that name. If it finds such a file, it creates a new PropertyResourceBundle object to hold it. Following on the previous example, it will return classes and and files giving preference as follows: (class) MyResources_fr_CH (file) MyResources_fr_CH.properties (class) MyResources_fr (file) MyResources_fr.properties (class) MyResources_en_US (file) MyResources_en_US.properties (class) MyResources_en (file) MyResources_en.properties (class) MyResources (file) MyResources.properties If a lookup fails, `getBundle()` throws a `MissingResourceException`.

The baseclass must be fully qualified (for example, `myPackage.MyResources`, not just `MyResources`). It must also be accessable by your code; it cannot be a class that is private to the package where `ResourceBundle.getBundle` is called.

Note: `ResourceBundle`s are used internally in accessing `NumberFormat`s, `Collation`s, and so on. The lookup strategy is the same.

Resource bundles contain key/value pairs. The keys uniquely identify a locale-specific object in the bundle. Here's an example of a `ListResourceBundle` that contains two key/value pairs:

>      class MyResource extends ListResourceBundle {
>           public Object[][] getContents() {
>                   return contents;
>           }
>           static final Object[][] contents = {
>           // LOCALIZE THIS
>                   {"OkKey", "OK"},
>                   {"CancelKey", "Cancel"},
>           // END OF MATERIAL TO LOCALIZE
>           };
>      }

Keys are always `String`s. In this example, the keys are `OkKey` and `CancelKey`. In the above example, the values are also `String`s--`OK` and `Cancel`--but they don't have to be. The values can be any type of object.

You retrieve an object from resource bundle using the appropriate getter method. Because `OkKey` and `CancelKey` are both strings, you would use `getString` to retrieve them:

>      button1 = new Button(myResourceBundle.getString("OkKey"));
>      button2 = new Button(myResourceBundle.getString("CancelKey"));

The getter methods all require the key as an argument and return the object if found. If the object is not found, the getter method throws a `MissingResourceException`.

Besides `getString`; ResourceBundle supports a number of other methods for getting different types of objects such as `getStringArray`. If you don't have an object that matches one of these methods, you can use `getObject` and cast the result to the appropriate type. For example:

>      int[] myIntegers = (int[]) myResources.getObject("intList");

NOTE: You should always supply a baseclass with no suffixes. This will be the class of "last resort", if a locale is requested that does not exist. In fact, you must provide all of the classes in any given inheritance chain that you provide a resource for. For example, if you provide `MyResources_fr_BE`, you must provide both `MyResources` and `MyResources_fr` or the resource bundle lookup won't work right.

The Java 2 platform provides two subclasses of `ResourceBundle`, `ListResourceBundle` and `PropertyResourceBundle`, that provide a fairly simple way to create resources. (Once serialization is fully integrated, we will provide another way.) As you saw briefly in a previous example, `ListResourceBundle` manages its resource as a List of key/value pairs. `PropertyResourceBundle` uses a properties file to manage its resources.

If `ListResourceBundle` or `PropertyResourceBundle` do not suit your needs, you can write your own `ResourceBundle` subclass. Your subclasses must override two methods: `handleGetObject` and `getKeys()`.

The following is a very simple example of a `ResourceBundle` subclass, MyResources, that manages two resources (for a larger number of resources you would probably use a `Hashtable`). Notice that if the key is not found, `handleGetObject` must return null. If the key is `null`, a `NullPointerException` should be thrown. Notice also that you don't need to supply a value if a "parent-level" `ResourceBundle` handles the same key with the same value (as in United Kingdom below). Also notice that because you specify an `en_GB` resource bundle, you also have to provide a default `en` resource bundle even though it inherits all its data from the root resource bundle.

Example:

>      // default (English language, United States)
>      abstract class MyResources extends ResourceBundle {
>          public Object handleGetObject(String key) {
>              if (key.equals("okKey")) return "Ok";
>              if (key.equals("cancelKey")) return "Cancel";
>          return null;
>          }
>      }

>      // German language
>      public class MyResources_de extends MyResources {
>          public Object handleGetObject(String key) {
>              // don't need okKey, since parent level handles it.
>              if (key.equals("cancelKey")) return "Abbrechen";
>              return null;
>          }
>      }

You do not have to restrict yourself to using a single family of `ResourceBundle`s. For example, you could have a set of bundles for exception messages, `ExceptionResources` (`ExceptionResources_fr`, `ExceptionResources_de`, ...), and one for widgets, `WidgetResource` (`WidgetResources_fr`, `WidgetResources_de`, ...); breaking up the resources however you like.

Since:
  JDK1.1
See Also:
  `ListResourceBundle`, `PropertyResourceBundle`, `MissingResourceException`

Field Summary
`protected ResourceBundle` | `parent` The parent bundle is consulted by getObject when this bundle does not contain a particular resource.

Constructor Summary
`ResourceBundle()` Sole constructor.

Method Summary
`static ResourceBundle` | `getBundle(String baseName)` Get the appropriate ResourceBundle subclass.
`static ResourceBundle` | `getBundle(String baseName, Locale locale)` Get the appropriate ResourceBundle subclass.
`static ResourceBundle` | `getBundle(String baseName, Locale locale, ClassLoader loader)` Get the appropriate ResourceBundle subclass.
`abstract Enumeration` | `getKeys()` Return an enumeration of the keys.
`Locale` | `getLocale()` Return the Locale for this ResourceBundle.
`Object` | `getObject(String key)` Get an object from a ResourceBundle.
`String` | `getString(String key)` Get an object from a ResourceBundle.
`String[]` | `getStringArray(String key)` Get an object from a ResourceBundle.
`protected abstract Object` | `handleGetObject(String key)` Get an object from a ResourceBundle.
`protected void` | `setParent(ResourceBundle parent)` Set the parent bundle of this bundle.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### parent

    protected ResourceBundle parent

  The parent bundle is consulted by getObject when this bundle does not contain a particular resource.

Constructor Detail

### ResourceBundle

    public ResourceBundle()

  Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method Detail

### getString

    public final String getString(String key)
                           throws MissingResourceException

  Get an object from a ResourceBundle.
  Convenience method to save casting.
  Parameters:
    `key` - see class description.
  Throws:
    `NullPointerException` - if `key` is `null`.

### getStringArray

    public final String[] getStringArray(String key)
                                  throws MissingResourceException

  Get an object from a ResourceBundle.
  Convenience method to save casting.
  Parameters:
    `key` - see class description.
  Throws:
    `NullPointerException` - if `key` is `null`.

### getObject

    public final Object getObject(String key)
                           throws MissingResourceException

  Get an object from a ResourceBundle.
  Parameters:
    `key` - see class description.
  Throws:
    `NullPointerException` - if `key` is `null`.

### getLocale

    public Locale getLocale()

  Return the Locale for this ResourceBundle. (This function can be used after a call to getBundle() to determine whether the ResourceBundle returned really corresponds to the requested locale or is a fallback.)

### setParent

    protected void setParent(ResourceBundle parent)

  Set the parent bundle of this bundle. The parent bundle is searched by getObject when this bundle does not contain a particular resource.
  Parameters:
    `parent` - this bundle's parent bundle.

### getBundle

    public static final ResourceBundle getBundle(String baseName)
                                          throws MissingResourceException

  Get the appropriate ResourceBundle subclass.
  Parameters:
    `baseName` - see class description.

### getBundle

    public static final ResourceBundle getBundle(String baseName,
                                                 Locale locale)

  Get the appropriate ResourceBundle subclass.
  Parameters:
    `baseName` - see class description.
    `locale` - see class description.

### getBundle

    public static ResourceBundle getBundle(String baseName,
                                           Locale locale,
                                           ClassLoader loader)
                                    throws MissingResourceException

  Get the appropriate ResourceBundle subclass.
  Parameters:
    `baseName` - see class description.
    `locale` - see class description.
    `loader` - the ClassLoader to load the resource from.

### handleGetObject

    protected abstract Object handleGetObject(String key)
                                       throws MissingResourceException

  Get an object from a ResourceBundle. NOTE: Subclasses must override.
  Parameters:
    `key` - see class description.
  Throws:
    `NullPointerException` - if `key` is `null`.

### getKeys

    public abstract Enumeration getKeys()

  Return an enumeration of the keys. NOTE: Subclasses must override.

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