Preferencespublic abstract class Preferences extends Object | A node in a hierarchical collection of preference data. This class
allows applications to store and retrieve user and system
preference and configuration data. This data is stored
persistently in an implementation-dependent backing store. Typical
implementations include flat files, OS-specific registries,
directory servers and SQL databases. The user of this class needn't
be concerned with details of the backing store.
There are two separate trees of preference nodes, one for user
preferences and one for system preferences. Each user has a separate user
preference tree, and all users in a given system share the same system
preference tree. The precise description of "user" and "system" will vary
from implementation to implementation. Typical information stored in the
user preference tree might include font choice, color choice, or preferred
window location and size for a particular application. Typical information
stored in the system preference tree might include installation
configuration data for an application.
Nodes in a preference tree are named in a similar fashion to
directories in a hierarchical file system. Every node in a preference
tree has a node name (which is not necessarily unique),
a unique absolute path name, and a path name relative to each
ancestor including itself.
The root node has a node name of the empty string (""). Every other
node has an arbitrary node name, specified at the time it is created. The
only restrictions on this name are that it cannot be the empty string, and
it cannot contain the slash character ('/').
The root node has an absolute path name of "/". Children of
the root node have absolute path names of "/" + <node
name>. All other nodes have absolute path names of <parent's
absolute path name> + "/" + <node name>.
Note that all absolute path names begin with the slash character.
A node n's path name relative to its ancestor a
is simply the string that must be appended to a's absolute path name
in order to form n's absolute path name, with the initial slash
character (if present) removed. Note that:
- No relative path names begin with the slash character.
- Every node's path name relative to itself is the empty string.
- Every node's path name relative to its parent is its node name (except
for the root node, which does not have a parent).
- Every node's path name relative to the root is its absolute path name
with the initial slash character removed.
Note finally that:
- No path name contains multiple consecutive slash characters.
- No path name with the exception of the root's absolute path name
ends in the slash character.
- Any string that conforms to these two rules is a valid path name.
All of the methods that modify preferences data are permitted to operate
asynchronously; they may return immediately, and changes will eventually
propagate to the persistent backing store with an implementation-dependent
delay. The flush method may be used to synchronously force
updates to the backing store. Normal termination of the Java Virtual
Machine will not result in the loss of pending updates -- an explicit
flush invocation is not required upon termination to ensure
that pending updates are made persistent.
All of the methods that read preferences from a Preferences
object require the invoker to provide a default value. The default value is
returned if no value has been previously set or if the backing store is
unavailable. The intent is to allow applications to operate, albeit
with slightly degraded functionality, even if the backing store becomes
unavailable. Several methods, like flush, have semantics that
prevent them from operating if the backing store is unavailable. Ordinary
applications should have no need to invoke any of these methods, which can
be identified by the fact that they are declared to throw {@link
BackingStoreException}.
The methods in this 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.
This class contains an export/import facility, allowing preferences
to be "exported" to an XML document, and XML documents representing
preferences to be "imported" back into the system. This facility
may be used to back up all or part of a preference tree, and
subsequently restore from the backup.
The XML document has the following DOCTYPE declaration:
<!DOCTYPE preferences SYSTEM "http://java.sun.com/dtd/preferences.dtd">
Note that the system URI (http://java.sun.com/dtd/preferences.dtd) is
not accessed when exporting or importing preferences; it merely
serves as a string to uniquely identify the DTD, which is:
<?xml version="1.0" encoding="UTF-8"?>
<!-- DTD for a Preferences tree. -->
<!-- The preferences element is at the root of an XML document
representing a Preferences tree. -->
<!ELEMENT preferences (root)>
<!-- The preferences element contains an optional version attribute,
which specifies version of DTD. -->
<!ATTLIST preferences EXTERNAL_XML_VERSION CDATA "0.0" >
<!-- The root element has a map representing the root's preferences
(if any), and one node for each child of the root (if any). -->
<!ELEMENT root (map, node*) >
<!-- Additionally, the root contains a type attribute, which
specifies whether it's the system or user root. -->
<!ATTLIST root
type (system|user) #REQUIRED >
<!-- Each node has a map representing its preferences (if any),
and one node for each child (if any). -->
<!ELEMENT node (map, node*) >
<!-- Additionally, each node has a name attribute -->
<!ATTLIST node
name CDATA #REQUIRED >
<!-- A map represents the preferences stored at a node (if any). -->
<!ELEMENT map (entry*) >
<!-- An entry represents a single preference, which is simply
a key-value pair. -->
<!ELEMENT entry EMPTY >
<!ATTLIST entry
key CDATA #REQUIRED
value CDATA #REQUIRED >
Every Preferences implementation must have an associated {@link
PreferencesFactory} implementation. Every Java(TM) SE implementation must provide
some means of specifying which PreferencesFactory implementation
is used to generate the root preferences nodes. This allows the
administrator to replace the default preferences implementation with an
alternative implementation.
Implementation note: In Sun's JRE, the PreferencesFactory
implementation is located as follows:
If the system property
java.util.prefs.PreferencesFactory is defined, then it is
taken to be the fully-qualified name of a class implementing the
PreferencesFactory interface. The class is loaded and
instantiated; if this process fails then an unspecified error is
thrown. If a PreferencesFactory implementation class file
has been installed in a jar file that is visible to the
{@link java.lang.ClassLoader#getSystemClassLoader system class loader},
and that jar file contains a provider-configuration file named
java.util.prefs.PreferencesFactory in the resource
directory META-INF/services, then the first class name
specified in that file is taken. If more than one such jar file is
provided, the first one found will be used. The class is loaded
and instantiated; if this process fails then an unspecified error
is thrown. Finally, if neither the above-mentioned system property nor
an extension jar file is provided, then the system-wide default
PreferencesFactory implementation for the underlying
platform is loaded and instantiated. |
| Fields Summary |
|---|
| private static final PreferencesFactory | factory | | public static final int | MAX_KEY_LENGTHMaximum length of string allowed as a key (80 characters). | | public static final int | MAX_VALUE_LENGTHMaximum length of string allowed as a value (8192 characters). | | public static final int | MAX_NAME_LENGTHMaximum length of a node name (80 characters). | | private static Permission | prefsPermThis permission object represents the permission required to get
access to the user or system root (which in turn allows for all
other operations). |
| Constructors Summary |
|---|
protected Preferences()Sole constructor. (For invocation by subclass constructors, typically
implicit.)
|
| Methods Summary |
|---|
| public abstract java.lang.String | absolutePath()Returns this preference node's absolute path name.
| | public abstract void | addNodeChangeListener(java.util.prefs.NodeChangeListener ncl)Registers the specified listener to receive node change events
for this node. A node change event is generated when a child node is
added to or removed from this node. (A single {@link #removeNode()}
invocation results in multiple node change events, one for every
node in the subtree rooted at the removed node.)
Events are only guaranteed for changes made within the same JVM
as the registered listener, though some implementations may generate
events for changes made outside this JVM. Events may be generated
before the changes have become permanent. Events are not generated
when indirect descendants of this node are added or removed; a
caller desiring such events must register with each descendant.
Few guarantees can be made regarding node creation. Because nodes
are created implicitly upon access, it may not be feasible for an
implementation to determine whether a child node existed in the backing
store prior to access (for example, because the backing store is
unreachable or cached information is out of date). Under these
circumstances, implementations are neither required to generate node
change events nor prohibited from doing so.
| | public abstract void | addPreferenceChangeListener(java.util.prefs.PreferenceChangeListener pcl)Registers the specified listener to receive preference change
events for this preference node. A preference change event is
generated when a preference is added to this node, removed from this
node, or when the value associated with a preference is changed.
(Preference change events are not generated by the {@link
#removeNode()} method, which generates a node change event.
Preference change events are generated by the clear
method.)
Events are only guaranteed for changes made within the same JVM
as the registered listener, though some implementations may generate
events for changes made outside this JVM. Events may be generated
before the changes have been made persistent. Events are not generated
when preferences are modified in descendants of this node; a caller
desiring such events must register with each descendant.
| | public abstract java.lang.String[] | childrenNames()Returns the names of the children of this preference node, relative to
this node. (The returned array will be of size zero if this node has
no children.)
| | public abstract void | clear()Removes all of the preferences (key-value associations) in this
preference node. This call has no effect on any descendants
of this node.
If this implementation supports stored defaults, and this
node in the preferences hierarchy contains any such defaults,
the stored defaults will be "exposed" by this call, in the sense that
they will be returned by succeeding calls to get.
| | public abstract void | exportNode(java.io.OutputStream os)Emits on the specified output stream an XML document representing all
of the preferences contained in this node (but not its descendants).
This XML document is, in effect, an offline backup of the node.
The XML document will have the following DOCTYPE declaration:
<!DOCTYPE preferences SYSTEM "http://java.sun.com/dtd/preferences.dtd">
The UTF-8 character encoding will be used.
This method is an exception to the general rule that the results of
concurrently executing multiple methods in this class yields
results equivalent to some serial execution. If the preferences
at this node are modified concurrently with an invocation of this
method, the exported preferences comprise a "fuzzy snapshot" of the
preferences contained in the node; some of the concurrent modifications
may be reflected in the exported data while others may not.
| | public abstract void | exportSubtree(java.io.OutputStream os)Emits an XML document representing all of the preferences contained
in this node and all of its descendants. This XML document is, in
effect, an offline backup of the subtree rooted at the node.
The XML document will have the following DOCTYPE declaration:
<!DOCTYPE preferences SYSTEM "http://java.sun.com/dtd/preferences.dtd">
The UTF-8 character encoding will be used.
This method is an exception to the general rule that the results of
concurrently executing multiple methods in this class yields
results equivalent to some serial execution. If the preferences
or nodes in the subtree rooted at this node are modified concurrently
with an invocation of this method, the exported preferences comprise a
"fuzzy snapshot" of the subtree; some of the concurrent modifications
may be reflected in the exported data while others may not.
| | private static java.util.prefs.PreferencesFactory | factory()
// 1. Try user-specified system property
String factoryName = AccessController.doPrivileged(
new PrivilegedAction<String>() {
public String run() {
return System.getProperty(
"java.util.prefs.PreferencesFactory");}});
if (factoryName != null) {
// FIXME: This code should be run in a doPrivileged and
// not use the context classloader, to avoid being
// dependent on the invoking thread.
// Checking AllPermission also seems wrong.
try {
return (PreferencesFactory)
Class.forName(factoryName, false,
ClassLoader.getSystemClassLoader())
.newInstance();
} catch (Exception ex) {
try {
// workaround for javaws, plugin,
// load factory class using non-system classloader
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(new java.security.AllPermission());
}
return (PreferencesFactory)
Class.forName(factoryName, false,
Thread.currentThread()
.getContextClassLoader())
.newInstance();
} catch (Exception e) {
InternalError error = new InternalError(
"Can't instantiate Preferences factory "
+ factoryName);
error.initCause(e);
throw error;
}
}
}
return AccessController.doPrivileged(
new PrivilegedAction<PreferencesFactory>() {
public PreferencesFactory run() {
return factory1();}});
| | private static java.util.prefs.PreferencesFactory | factory1()
// 2. Try service provider interface
Iterator i = Service.providers(PreferencesFactory.class,
ClassLoader.getSystemClassLoader());
// choose first provider instance
while (i.hasNext()) {
try {
return (PreferencesFactory) i.next();
} catch (ServiceConfigurationError sce) {
if (sce.getCause() instanceof SecurityException) {
// Ignore the security exception, try the next provider
continue;
}
throw sce;
}
}
// 3. Use platform-specific system-wide default
String platformFactory =
System.getProperty("os.name").startsWith("Windows")
? "java.util.prefs.WindowsPreferencesFactory"
: "java.util.prefs.FileSystemPreferencesFactory";
try {
return (PreferencesFactory)
Class.forName(platformFactory, false, null).newInstance();
} catch (Exception e) {
InternalError error = new InternalError(
"Can't instantiate platform default Preferences factory "
+ platformFactory);
error.initCause(e);
throw error;
}
| | public abstract void | flush()Forces any changes in the contents of this preference node and its
descendants to the persistent store. Once this method returns
successfully, it is safe to assume that all changes made in the
subtree rooted at this node prior to the method invocation have become
permanent.
Implementations are free to flush changes into the persistent store
at any time. They do not need to wait for this method to be called.
When a flush occurs on a newly created node, it is made persistent,
as are any ancestors (and descendants) that have yet to be made
persistent. Note however that any preference value changes in
ancestors are not guaranteed to be made persistent.
If this method is invoked on a node that has been removed with
the {@link #removeNode()} method, flushSpi() is invoked on this node,
but not on others.
| | public abstract java.lang.String | get(java.lang.String key, java.lang.String def)Returns the value associated with the specified key in this preference
node. Returns the specified default if there is no value associated
with the key, or the backing store is inaccessible.
Some implementations may store default values in their backing
stores. If there is no value associated with the specified key
but there is such a stored default, it is returned in
preference to the specified default.
| | public abstract boolean | getBoolean(java.lang.String key, boolean def)Returns the boolean value represented by the string associated with the
specified key in this preference node. Valid strings
are "true", which represents true, and "false", which
represents false. Case is ignored, so, for example, "TRUE"
and "False" are also valid. This method is intended for use in
conjunction with {@link #putBoolean}.
Returns the specified default if there is no value
associated with the key, the backing store is inaccessible, or if the
associated value is something other than "true" or
"false", ignoring case.
If the implementation supports stored defaults and such a
default exists and is accessible, it is used in preference to the
specified default, unless the stored default is something other than
"true" or "false", ignoring case, in which case the
specified default is used.
| | public abstract byte[] | getByteArray(java.lang.String key, byte[] def)Returns the byte array value represented by the string associated with
the specified key in this preference node. Valid strings are
Base64 encoded binary data, as defined in RFC 2045, Section 6.8,
with one minor change: the string must consist solely of characters
from the Base64 Alphabet; no newline characters or
extraneous characters are permitted. This method is intended for use
in conjunction with {@link #putByteArray}.
Returns the specified default if there is no value
associated with the key, the backing store is inaccessible, or if the
associated value is not a valid Base64 encoded byte array
(as defined above).
If the implementation supports stored defaults and such a
default exists and is accessible, it is used in preference to the
specified default, unless the stored default is not a valid Base64
encoded byte array (as defined above), in which case the
specified default is used.
| | public abstract double | getDouble(java.lang.String key, double def)Returns the double value represented by the string associated with the
specified key in this preference node. The string is converted to an
integer as by {@link Double#parseDouble(String)}. Returns the specified
default if there is no value associated with the key, the backing store
is inaccessible, or if Double.parseDouble(String) would throw a
{@link NumberFormatException} if the associated value were passed.
This method is intended for use in conjunction with {@link #putDouble}.
If the implementation supports stored defaults and such a
default exists, is accessible, and could be converted to a double
with Double.parseDouble, this double is returned in preference
to the specified default.
| | public abstract float | getFloat(java.lang.String key, float def)Returns the float value represented by the string associated with the
specified key in this preference node. The string is converted to an
integer as by {@link Float#parseFloat(String)}. Returns the specified
default if there is no value associated with the key, the backing store
is inaccessible, or if Float.parseFloat(String) would throw a
{@link NumberFormatException} if the associated value were passed.
This method is intended for use in conjunction with {@link #putFloat}.
If the implementation supports stored defaults and such a
default exists, is accessible, and could be converted to a float
with Float.parseFloat, this float is returned in preference to
the specified default.
| | public abstract int | getInt(java.lang.String key, int def)Returns the int value represented by the string associated with the
specified key in this preference node. The string is converted to
an integer as by {@link Integer#parseInt(String)}. Returns the
specified default if there is no value associated with the key,
the backing store is inaccessible, or if
Integer.parseInt(String) would throw a {@link
NumberFormatException} if the associated value were passed. This
method is intended for use in conjunction with {@link #putInt}.
If the implementation supports stored defaults and such a
default exists, is accessible, and could be converted to an int
with Integer.parseInt, this int is returned in preference to
the specified default.
| | public abstract long | getLong(java.lang.String key, long def)Returns the long value represented by the string associated with the
specified key in this preference node. The string is converted to
a long as by {@link Long#parseLong(String)}. Returns the
specified default if there is no value associated with the key,
the backing store is inaccessible, or if
Long.parseLong(String) would throw a {@link
NumberFormatException} if the associated value were passed. This
method is intended for use in conjunction with {@link #putLong}.
If the implementation supports stored defaults and such a
default exists, is accessible, and could be converted to a long
with Long.parseLong, this long is returned in preference to
the specified default.
| | public static void | importPreferences(java.io.InputStream is)Imports all of the preferences represented by the XML document on the
specified input stream. The document may represent user preferences or
system preferences. If it represents user preferences, the preferences
will be imported into the calling user's preference tree (even if they
originally came from a different user's preference tree). If any of
the preferences described by the document inhabit preference nodes that
do not exist, the nodes will be created.
The XML document must have the following DOCTYPE declaration:
<!DOCTYPE preferences SYSTEM "http://java.sun.com/dtd/preferences.dtd">
(This method is designed for use in conjunction with
{@link #exportNode(OutputStream)} and
{@link #exportSubtree(OutputStream)}.
This method is an exception to the general rule that the results of
concurrently executing multiple methods in this class yields
results equivalent to some serial execution. The method behaves
as if implemented on top of the other public methods in this class,
notably {@link #node(String)} and {@link #put(String, String)}.
XmlSupport.importPreferences(is);
| | public abstract boolean | isUserNode()Returns true if this preference node is in the user
preference tree, false if it's in the system preference tree.
| | public abstract java.lang.String[] | keys()Returns all of the keys that have an associated value in this
preference node. (The returned array will be of size zero if
this node has no preferences.)
If the implementation supports stored defaults and there
are any such defaults at this node that have not been overridden,
by explicit preferences, the defaults are returned in the array in
addition to any explicit preferences.
| | public abstract java.lang.String | name()Returns this preference node's name, relative to its parent.
| | public abstract java.util.prefs.Preferences | node(java.lang.String pathName)Returns the named preference node in the same tree as this node,
creating it and any of its ancestors if they do not already exist.
Accepts a relative or absolute path name. Relative path names
(which do not begin with the slash character ('/')) are
interpreted relative to this preference node.
If the returned node did not exist prior to this call, this node and
any ancestors that were created by this call are not guaranteed
to become permanent until the flush method is called on
the returned node (or one of its ancestors or descendants).
| | public abstract boolean | nodeExists(java.lang.String pathName)Returns true if the named preference node exists in the same tree
as this node. Relative path names (which do not begin with the slash
character ('/')) are interpreted relative to this preference
node.
If this node (or an ancestor) has already been removed with the
{@link #removeNode()} method, it is legal to invoke this method,
but only with the path name ""; the invocation will return
false. Thus, the idiom p.nodeExists("") may be
used to test whether p has been removed.
| | private static java.lang.String | nodeName(java.lang.Class c)Returns the absolute path name of the node corresponding to the package
of the specified object.
if (c.isArray())
throw new IllegalArgumentException(
"Arrays have no associated preferences node.");
String className = c.getName();
int pkgEndIndex = className.lastIndexOf('.");
if (pkgEndIndex < 0)
return "/<unnamed>";
String packageName = className.substring(0, pkgEndIndex);
return "/" + packageName.replace('.", '/");
| | public abstract java.util.prefs.Preferences | parent()Returns the parent of this preference node, or null if this is
the root.
| | public abstract void | put(java.lang.String key, java.lang.String value)Associates the specified value with the specified key in this
preference node.
| | public abstract void | putBoolean(java.lang.String key, boolean value)Associates a string representing the specified boolean value with the
specified key in this preference node. The associated string is
"true" if the value is true, and "false" if it is
false. This method is intended for use in conjunction with
{@link #getBoolean}.
| | public abstract void | putByteArray(java.lang.String key, byte[] value)Associates a string representing the specified byte array with the
specified key in this preference node. The associated string is
the Base64 encoding of the byte array, as defined in RFC 2045, Section 6.8,
with one minor change: the string will consist solely of characters
from the Base64 Alphabet; it will not contain any newline
characters. Note that the maximum length of the byte array is limited
to three quarters of MAX_VALUE_LENGTH so that the length
of the Base64 encoded String does not exceed MAX_VALUE_LENGTH.
This method is intended for use in conjunction with
{@link #getByteArray}.
| | public abstract void | putDouble(java.lang.String key, double value)Associates a string representing the specified double value with the
specified key in this preference node. The associated string is the
one that would be returned if the double value were passed to
{@link Double#toString(double)}. This method is intended for use in
conjunction with {@link #getDouble}.
| | public abstract void | putFloat(java.lang.String key, float value)Associates a string representing the specified float value with the
specified key in this preference node. The associated string is the
one that would be returned if the float value were passed to
{@link Float#toString(float)}. This method is intended for use in
conjunction with {@link #getFloat}.
| | public abstract void | putInt(java.lang.String key, int value)Associates a string representing the specified int value with the
specified key in this preference node. The associated string is the
one that would be returned if the int value were passed to
{@link Integer#toString(int)}. This method is intended for use in
conjunction with {@link #getInt}.
| | public abstract void | putLong(java.lang.String key, long value)Associates a string representing the specified long value with the
specified key in this preference node. The associated string is the
one that would be returned if the long value were passed to
{@link Long#toString(long)}. This method is intended for use in
conjunction with {@link #getLong}.
| | public abstract void | remove(java.lang.String key)Removes the value associated with the specified key in this preference
node, if any.
If this implementation supports stored defaults, and there is
such a default for the specified preference, the stored default will be
"exposed" by this call, in the sense that it will be returned
by a succeeding call to get.
| | public abstract void | removeNode()Removes this preference node and all of its descendants, invalidating
any preferences contained in the removed nodes. Once a node has been
removed, attempting any method other than {@link #name()},
{@link #absolutePath()}, {@link #isUserNode()}, {@link #flush()} or
{@link #node(String) nodeExists("")} on the corresponding
Preferences instance will fail with an
IllegalStateException. (The methods defined on {@link Object}
can still be invoked on a node after it has been removed; they will not
throw IllegalStateException.)
The removal is not guaranteed to be persistent until the
flush method is called on this node (or an ancestor).
If this implementation supports stored defaults, removing a
node exposes any stored defaults at or below this node. Thus, a
subsequent call to nodeExists on this node's path name may
return true, and a subsequent call to node on this
path name may return a (different) Preferences instance
representing a non-empty collection of preferences and/or children.
| | public abstract void | removeNodeChangeListener(java.util.prefs.NodeChangeListener ncl)Removes the specified NodeChangeListener, so it no longer
receives change events.
| | public abstract void | removePreferenceChangeListener(java.util.prefs.PreferenceChangeListener pcl)Removes the specified preference change listener, so it no longer
receives preference change events.
| | public abstract void | sync()Ensures that future reads from this preference node and its
descendants reflect any changes that were committed to the persistent
store (from any VM) prior to the sync invocation. As a
side-effect, forces any changes in the contents of this preference node
and its descendants to the persistent store, as if the flush
method had been invoked on this node.
| | public static java.util.prefs.Preferences | systemNodeForPackage(java.lang.Class c)Returns the preference node from the system preference tree that is
associated (by convention) with the specified class's package. The
convention is as follows: the absolute path name of the node is the
fully qualified package name, preceded by a slash ('/'), and
with each period ('.') replaced by a slash. For example the
absolute path name of the node associated with the class
com.acme.widget.Foo is /com/acme/widget.
This convention does not apply to the unnamed package, whose
associated preference node is <unnamed>. This node
is not intended for long term use, but for convenience in the early
development of programs that do not yet belong to a package, and
for "throwaway" programs. Valuable data should not be stored
at this node as it is shared by all programs that use it.
A class Foo wishing to access preferences pertaining to its
package can obtain a preference node as follows:
static Preferences prefs = Preferences.systemNodeForPackage(Foo.class);
This idiom obviates the need for using a string to describe the
preferences node and decreases the likelihood of a run-time failure.
(If the class name is misspelled, it will typically result in a
compile-time error.)
Invoking this method will result in the creation of the returned
node and its ancestors if they do not already exist. If the returned
node did not exist prior to this call, this node and any ancestors that
were created by this call are not guaranteed to become permanent until
the flush method is called on the returned node (or one of its
ancestors or descendants).
return systemRoot().node(nodeName(c));
| | public static java.util.prefs.Preferences | systemRoot()Returns the root preference node for the system.
SecurityManager security = System.getSecurityManager();
if (security != null)
security.checkPermission(prefsPerm);
return factory.systemRoot();
| | public abstract java.lang.String | toString()Returns a string representation of this preferences node,
as if computed by the expression:(this.isUserNode() ? "User" :
"System") + " Preference Node: " + this.absolutePath().
| | public static java.util.prefs.Preferences | userNodeForPackage(java.lang.Class c)Returns the preference node from the calling user's preference tree
that is associated (by convention) with the specified class's package.
The convention is as follows: the absolute path name of the node is the
fully qualified package name, preceded by a slash ('/'), and
with each period ('.') replaced by a slash. For example the
absolute path name of the node associated with the class
com.acme.widget.Foo is /com/acme/widget.
This convention does not apply to the unnamed package, whose
associated preference node is <unnamed>. This node
is not intended for long term use, but for convenience in the early
development of programs that do not yet belong to a package, and
for "throwaway" programs. Valuable data should not be stored
at this node as it is shared by all programs that use it.
A class Foo wishing to access preferences pertaining to its
package can obtain a preference node as follows:
static Preferences prefs = Preferences.userNodeForPackage(Foo.class);
This idiom obviates the need for using a string to describe the
preferences node and decreases the likelihood of a run-time failure.
(If the class name is misspelled, it will typically result in a
compile-time error.)
Invoking this method will result in the creation of the returned
node and its ancestors if they do not already exist. If the returned
node did not exist prior to this call, this node and any ancestors that
were created by this call are not guaranteed to become permanent until
the flush method is called on the returned node (or one of its
ancestors or descendants).
return userRoot().node(nodeName(c));
| | public static java.util.prefs.Preferences | userRoot()Returns the root preference node for the calling user.
SecurityManager security = System.getSecurityManager();
if (security != null)
security.checkPermission(prefsPerm);
return factory.userRoot();
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