The methods in this class may be invoked concurrently by multiple threads OrdinaryĪpplications should have no need to invoke any of these methods, which canīe identified by the fact that they are declared to throw BackingStoreException. Prevent them from operating if the backing store is unavailable. Several methods, like flush, have semantics that With slightly degraded functionality, even if the backing store becomes The intent is to allow applications to operate, albeit Returned if no value has been previously set or if the backing store is Object require the invoker to provide a default value. That pending updates are made persistent.Īll of the methods that read preferences from a Preferences Machine will not result in the loss of pending updates - an explicitįlush invocation is not required upon termination to ensure The flush method may be used to synchronously force Propagate to the persistent backing store with an implementation-dependentĭelay.
Any string that conforms to these two rules is a valid path name.Īll of the methods that modify preferences data are permitted to operateĪsynchronously they may return immediately, and changes will eventually. No path name with the exception of the root's absolute path name. 
No path name contains multiple consecutive slash characters. With the initial slash character removed. Every node's path name relative to the root is its absolute path name. Every node's path name relative to its parent is its node name (exceptįor the root node, which does not have a parent). Every node's path name relative to itself is the empty string. No relative path names begin with the slash character. In order to form n's absolute path name, with the initial slashĬharacter (if present) removed. Is simply the string that must be appended to a's absolute path name Note that all absolute path names begin with the slash character.Ī node n's path name relative to its ancestor a All other nodes have absolute path names of + "/" +. The root node have absolute path names of "/" +. The root node has an absolute path name of "/". It cannot contain the slash character ('/'). Only restrictions on this name are that it cannot be the empty string, and Node has an arbitrary node name, specified at the time it is created. The root node has a node name of the empty string (""). Tree has a node name (which is not necessarily unique),Ī unique absolute path name, and a path name relative to each Nodes in a preference tree are named in a similar fashion toĭirectories in a hierarchical file system. Stored in the system preference tree might include installation Window location and size for a particular application. User preference tree might include font choice, color choice, or preferred The precise description of "user" and "system" will varyįrom implementation to implementation. Preference tree, and all users in a given system share the same system Preferences and one for system preferences. There are two separate trees of preference nodes, one for user The user of this class needn'tīe concerned with details of the backing store. Implementations include flat files, OS-specific registries,ĭirectory servers and SQL databases. Persistently in an implementation-dependent backing store. This classĪllows applications to store and retrieve user and system A node in a hierarchical collection of preference data.
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