7 Preferences API
The Preferences API enables applications to manage preference and configuration data.
Applications require preference and configuration data to adapt to the needs of different users and environments. The java.util.prefs package provides a way for applications to store and retrieve user and system preference and configuration data. The data is stored persistently in an implementation-dependent backing store. There are two separate trees of preference nodes: one for user preferences and one for system preferences.
All of the methods that modify preference data are permitted to operate asynchronously. They may return immediately, and changes will eventually propagate to the persistent backing store. The flush method can be used to force changes to the backing store.
The methods in the Preferences class may be invoked concurrently by multiple threads in a single JVM without the need for external synchronization, and the results will be equivalent to some serial execution. If this class is used concurrently by multiple JVMs that store their preference data in the same backing store, the data store will not be corrupted, but no other guarantees are made concerning the consistency of the preference data.