Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Constants](https://developer.android.com/reference/java/util/prefs/Preferences#constants) \| [Protected Ctors](https://developer.android.com/reference/java/util/prefs/Preferences#proctors) \| [Methods](https://developer.android.com/reference/java/util/prefs/Preferences#pubmethods) \| [Inherited Methods](https://developer.android.com/reference/java/util/prefs/Preferences#inhmethods)

# Preferences


`
public


abstract
class
Preferences
`


`

extends https://developer.android.com/reference/java/lang/Object


`

`


`

|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||
| ↳ | java.util.prefs.Preferences |

|---|
| Known direct subclasses [AbstractPreferences](https://developer.android.com/reference/java/util/prefs/AbstractPreferences) |---|---| | [AbstractPreferences](https://developer.android.com/reference/java/util/prefs/AbstractPreferences) | This class provides a skeletal implementation of the `https://developer.android.com/reference/java/util/prefs/Preferences` class, greatly easing the task of implementing it. | |

<br />

*** ** * ** ***

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 `https://developer.android.com/reference/java/util/prefs/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 `https://developer.android.com/reference/java/util/prefs/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:

1. 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.

2. If a PreferencesFactory implementation class file
   has been installed in a jar file that is visible to the
   `https://developer.android.com/reference/java/lang/ClassLoader#getSystemClassLoader()`,
   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.

3. 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.

<br />

## Summary

| ### Constants ||
|---|---|
| `int` | `https://developer.android.com/reference/java/util/prefs/Preferences#MAX_KEY_LENGTH` Maximum length of string allowed as a key (80 characters). |
| `int` | `https://developer.android.com/reference/java/util/prefs/Preferences#MAX_NAME_LENGTH` Maximum length of a node name (80 characters). |
| `int` | `https://developer.android.com/reference/java/util/prefs/Preferences#MAX_VALUE_LENGTH` Maximum length of string allowed as a value (8192 characters). |

| ### Protected constructors ||
|---|---|
| ` https://developer.android.com/reference/java/util/prefs/Preferences#Preferences()() ` Sole constructor. |

| ### Public methods ||
|---|---|
| ` abstract https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/prefs/Preferences#absolutePath()() ` Returns this preference node's absolute path name. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#addNodeChangeListener(java.util.prefs.NodeChangeListener)(https://developer.android.com/reference/java/util/prefs/NodeChangeListener ncl) ` Registers the specified listener to receive *node change events* for this node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#addPreferenceChangeListener(java.util.prefs.PreferenceChangeListener)(https://developer.android.com/reference/java/util/prefs/PreferenceChangeListener pcl) ` Registers the specified listener to receive *preference change events* for this preference node. |
| ` abstract https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/prefs/Preferences#childrenNames()() ` Returns the names of the children of this preference node, relative to this node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#clear()() ` Removes all of the preferences (key-value associations) in this preference node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#exportNode(java.io.OutputStream)(https://developer.android.com/reference/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). |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#exportSubtree(java.io.OutputStream)(https://developer.android.com/reference/java/io/OutputStream os) ` Emits an XML document representing all of the preferences contained in this node and all of its descendants. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#flush()() ` Forces any changes in the contents of this preference node and its descendants to the persistent store. |
| ` abstract https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)(https://developer.android.com/reference/java/lang/String key, https://developer.android.com/reference/java/lang/String def) ` Returns the value associated with the specified key in this preference node. |
| ` abstract boolean` | ` https://developer.android.com/reference/java/util/prefs/Preferences#getBoolean(java.lang.String,%20boolean)(https://developer.android.com/reference/java/lang/String key, boolean def) ` Returns the boolean value represented by the string associated with the specified key in this preference node. |
| ` abstract byte[]` | ` https://developer.android.com/reference/java/util/prefs/Preferences#getByteArray(java.lang.String,%20byte[])(https://developer.android.com/reference/java/lang/String key, byte[] def) ` Returns the byte array value represented by the string associated with the specified key in this preference node. |
| ` abstract double` | ` https://developer.android.com/reference/java/util/prefs/Preferences#getDouble(java.lang.String,%20double)(https://developer.android.com/reference/java/lang/String key, double def) ` Returns the double value represented by the string associated with the specified key in this preference node. |
| ` abstract float` | ` https://developer.android.com/reference/java/util/prefs/Preferences#getFloat(java.lang.String,%20float)(https://developer.android.com/reference/java/lang/String key, float def) ` Returns the float value represented by the string associated with the specified key in this preference node. |
| ` abstract int` | ` https://developer.android.com/reference/java/util/prefs/Preferences#getInt(java.lang.String,%20int)(https://developer.android.com/reference/java/lang/String key, int def) ` Returns the int value represented by the string associated with the specified key in this preference node. |
| ` abstract long` | ` https://developer.android.com/reference/java/util/prefs/Preferences#getLong(java.lang.String,%20long)(https://developer.android.com/reference/java/lang/String key, long def) ` Returns the long value represented by the string associated with the specified key in this preference node. |
| ` static void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#importPreferences(java.io.InputStream)(https://developer.android.com/reference/java/io/InputStream is) ` Imports all of the preferences represented by the XML document on the specified input stream. |
| ` abstract boolean` | ` https://developer.android.com/reference/java/util/prefs/Preferences#isUserNode()() ` Returns true if this preference node is in the user preference tree, false if it's in the system preference tree. |
| ` abstract https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/prefs/Preferences#keys()() ` Returns all of the keys that have an associated value in this preference node. |
| ` abstract https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/prefs/Preferences#name()() ` Returns this preference node's name, relative to its parent. |
| ` abstract https://developer.android.com/reference/java/util/prefs/Preferences` | ` https://developer.android.com/reference/java/util/prefs/Preferences#node(java.lang.String)(https://developer.android.com/reference/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. |
| ` abstract boolean` | ` https://developer.android.com/reference/java/util/prefs/Preferences#nodeExists(java.lang.String)(https://developer.android.com/reference/java/lang/String pathName) ` Returns true if the named preference node exists in the same tree as this node. |
| ` abstract https://developer.android.com/reference/java/util/prefs/Preferences` | ` https://developer.android.com/reference/java/util/prefs/Preferences#parent()() ` Returns the parent of this preference node, or null if this is the root. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#put(java.lang.String,%20java.lang.String)(https://developer.android.com/reference/java/lang/String key, https://developer.android.com/reference/java/lang/String value) ` Associates the specified value with the specified key in this preference node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#putBoolean(java.lang.String,%20boolean)(https://developer.android.com/reference/java/lang/String key, boolean value) ` Associates a string representing the specified boolean value with the specified key in this preference node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#putByteArray(java.lang.String,%20byte[])(https://developer.android.com/reference/java/lang/String key, byte[] value) ` Associates a string representing the specified byte array with the specified key in this preference node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#putDouble(java.lang.String,%20double)(https://developer.android.com/reference/java/lang/String key, double value) ` Associates a string representing the specified double value with the specified key in this preference node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#putFloat(java.lang.String,%20float)(https://developer.android.com/reference/java/lang/String key, float value) ` Associates a string representing the specified float value with the specified key in this preference node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#putInt(java.lang.String,%20int)(https://developer.android.com/reference/java/lang/String key, int value) ` Associates a string representing the specified int value with the specified key in this preference node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#putLong(java.lang.String,%20long)(https://developer.android.com/reference/java/lang/String key, long value) ` Associates a string representing the specified long value with the specified key in this preference node. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#remove(java.lang.String)(https://developer.android.com/reference/java/lang/String key) ` Removes the value associated with the specified key in this preference node, if any. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()() ` Removes this preference node and all of its descendants, invalidating any preferences contained in the removed nodes. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#removeNodeChangeListener(java.util.prefs.NodeChangeListener)(https://developer.android.com/reference/java/util/prefs/NodeChangeListener ncl) ` Removes the specified NodeChangeListener, so it no longer receives change events. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#removePreferenceChangeListener(java.util.prefs.PreferenceChangeListener)(https://developer.android.com/reference/java/util/prefs/PreferenceChangeListener pcl) ` Removes the specified preference change listener, so it no longer receives preference change events. |
| ` abstract void` | ` https://developer.android.com/reference/java/util/prefs/Preferences#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. |
| ` static https://developer.android.com/reference/java/util/prefs/Preferences` | ` https://developer.android.com/reference/java/util/prefs/Preferences#systemNodeForPackage(java.lang.Class<?>)(https://developer.android.com/reference/java/lang/Class<?> c) ` **WARNING:** On Android, the Preference nodes corresponding to the "system" and "user" preferences are stored in sections of the file system that are inaccessible to apps. |
| ` static https://developer.android.com/reference/java/util/prefs/Preferences` | ` https://developer.android.com/reference/java/util/prefs/Preferences#systemRoot()() ` **WARNING:** On Android, the Preference nodes corresponding to the "system" and "user" preferences are stored in sections of the file system that are inaccessible to apps. |
| ` abstract https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/prefs/Preferences#toString()() ` Returns a string representation of this preferences node, as if computed by the expression:(this.isUserNode() ? "User" : "System") + " Preference Node: " + this.absolutePath(). |
| ` static https://developer.android.com/reference/java/util/prefs/Preferences` | ` https://developer.android.com/reference/java/util/prefs/Preferences#userNodeForPackage(java.lang.Class<?>)(https://developer.android.com/reference/java/lang/Class<?> c) ` **WARNING:** On Android, the Preference nodes corresponding to the "system" and "user" preferences are stored in sections of the file system that are inaccessible to apps. |
| ` static https://developer.android.com/reference/java/util/prefs/Preferences` | ` https://developer.android.com/reference/java/util/prefs/Preferences#userRoot()() ` **WARNING:** On Android, the Preference nodes corresponding to the "system" and "user" preferences are stored in sections of the file system that are inaccessible to apps. |

| ### Inherited methods |
|---|---|
| From class ` https://developer.android.com/reference/java/lang/Object ` |---|---| | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/lang/Object#clone()() ` Creates and returns a copy of this object. | | ` boolean` | ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` https://developer.android.com/reference/java/lang/Object#finalize()() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final https://developer.android.com/reference/java/lang/Class<?>` | ` https://developer.android.com/reference/java/lang/Object#getClass()() ` Returns the runtime class of this `Object`. | | ` int` | ` https://developer.android.com/reference/java/lang/Object#hashCode()() ` Returns a hash code value for the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notify()() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notifyAll()() ` Wakes up all threads that are waiting on this object's monitor. | | ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/lang/Object#toString()() ` Returns a string representation of the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait()() ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*. | ||

## Constants

### MAX_KEY_LENGTH

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static final int MAX_KEY_LENGTH
```

Maximum length of string allowed as a key (80 characters).

<br />

Constant Value:

80
(0x00000050)


### MAX_NAME_LENGTH

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static final int MAX_NAME_LENGTH
```

Maximum length of a node name (80 characters).

<br />

Constant Value:

80
(0x00000050)


### MAX_VALUE_LENGTH

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static final int MAX_VALUE_LENGTH
```

Maximum length of string allowed as a value (8192 characters).

<br />

Constant Value:

8192
(0x00002000)


## Protected constructors

### Preferences

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected Preferences ()
```

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

<br />

## Public methods

### absolutePath

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract String absolutePath ()
```

Returns this preference node's absolute path name.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | this preference node's absolute path name. <br /> |

### addNodeChangeListener

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void addNodeChangeListener (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 `https://developer.android.com/reference/java/util/prefs/Preferences#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.

<br />

| Parameters ||
|---|---|
| `ncl` | `NodeChangeListener`: The NodeChangeListener to add. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if ncl is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#removeNodeChangeListener(java.util.prefs.NodeChangeListener)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#addPreferenceChangeListener(java.util.prefs.PreferenceChangeListener)`

### addPreferenceChangeListener

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void addPreferenceChangeListener (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 `https://developer.android.com/reference/java/util/prefs/Preferences#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.

<br />

| Parameters ||
|---|---|
| `pcl` | `PreferenceChangeListener`: The preference change listener to add. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if pcl is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#removePreferenceChangeListener(java.util.prefs.PreferenceChangeListener)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#addNodeChangeListener(java.util.prefs.NodeChangeListener)`

### childrenNames

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract 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.)

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | the names of the children of this preference node. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if this operation cannot be completed due to a failure in the backing store, or inability to communicate with it. |

### clear

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if this operation cannot be completed due to a failure in the backing store, or inability to communicate with it. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()`

### exportNode

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void exportNode (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.

<br />

| Parameters ||
|---|---|
| `os` | `OutputStream`: the output stream on which to emit the XML document. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/IOException` | if writing to the specified output stream results in an IOException. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if preference data cannot be read from backing store. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#importPreferences(java.io.InputStream)`

### exportSubtree

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void exportSubtree (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.

<br />

| Parameters ||
|---|---|
| `os` | `OutputStream`: the output stream on which to emit the XML document. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/IOException` | if writing to the specified output stream results in an IOException. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if preference data cannot be read from backing store. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#importPreferences(java.io.InputStream)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#exportNode(java.io.OutputStream)`

### flush

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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 `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method, flushSpi() is invoked on this node,
but not on others.

<br />

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if this operation cannot be completed due to a failure in the backing store, or inability to communicate with it. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#sync()`

### get

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract String get (String key, 
                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.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key whose associated value is to be returned. <br /> |
| `def` | `String`: the value to be returned in the event that this preference node has no value associated with key. <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | the value associated with key, or def if no value is associated with key, or the backing store is inaccessible. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. (A null value for def *is* permitted.) |

### getBoolean

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract boolean getBoolean (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 `https://developer.android.com/reference/java/util/prefs/Preferences#putBoolean(java.lang.String,%20boolean)`.

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.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key whose associated value is to be returned as a boolean. <br /> |
| `def` | `boolean`: the value to be returned in the event that this preference node has no value associated with key or the associated value cannot be interpreted as a boolean, or the backing store is inaccessible. <br /> |

| Returns ||
|---|---|
| `boolean` | the boolean value represented by the string associated with key in this preference node, or def if the associated value does not exist or cannot be interpreted as a boolean. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#putBoolean(java.lang.String,%20boolean)`

### getByteArray

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract byte[] getByteArray (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](http://www.ietf.org/rfc/rfc2045.txt), 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 `https://developer.android.com/reference/java/util/prefs/Preferences#putByteArray(java.lang.String,%20byte[])`.

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.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key whose associated value is to be returned as a byte array. <br /> |
| `def` | `byte`: the value to be returned in the event that this preference node has no value associated with key or the associated value cannot be interpreted as a byte array, or the backing store is inaccessible. <br /> |

| Returns ||
|---|---|
| `byte[]` | the byte array value represented by the string associated with key in this preference node, or def if the associated value does not exist or cannot be interpreted as a byte array. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. (A null value for def *is* permitted.) |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#putByteArray(java.lang.String,%20byte[])`

### getDouble

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract double getDouble (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 `https://developer.android.com/reference/java/lang/Double#parseDouble(java.lang.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
`https://developer.android.com/reference/java/lang/NumberFormatException` if the associated value were passed.
This method is intended for use in conjunction with `https://developer.android.com/reference/java/util/prefs/Preferences#putDouble(java.lang.String,%20double)`.

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.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key whose associated value is to be returned as a double. <br /> |
| `def` | `double`: the value to be returned in the event that this preference node has no value associated with key or the associated value cannot be interpreted as a double, or the backing store is inaccessible. <br /> |

| Returns ||
|---|---|
| `double` | the double value represented by the string associated with key in this preference node, or def if the associated value does not exist or cannot be interpreted as a double. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#putDouble(java.lang.String,%20double)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)`

### getFloat

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract float getFloat (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 `https://developer.android.com/reference/java/lang/Float#parseFloat(java.lang.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
`https://developer.android.com/reference/java/lang/NumberFormatException` if the associated value were passed.
This method is intended for use in conjunction with `https://developer.android.com/reference/java/util/prefs/Preferences#putFloat(java.lang.String,%20float)`.

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.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key whose associated value is to be returned as a float. <br /> |
| `def` | `float`: the value to be returned in the event that this preference node has no value associated with key or the associated value cannot be interpreted as a float, or the backing store is inaccessible. <br /> |

| Returns ||
|---|---|
| `float` | the float value represented by the string associated with key in this preference node, or def if the associated value does not exist or cannot be interpreted as a float. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#putFloat(java.lang.String,%20float)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)`

### getInt

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract int getInt (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 `https://developer.android.com/reference/java/lang/Integer#parseInt(java.lang.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 `https://developer.android.com/reference/java/lang/NumberFormatException` if the associated value were passed. This
method is intended for use in conjunction with `https://developer.android.com/reference/java/util/prefs/Preferences#putInt(java.lang.String,%20int)`.

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.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key whose associated value is to be returned as an int. <br /> |
| `def` | `int`: the value to be returned in the event that this preference node has no value associated with key or the associated value cannot be interpreted as an int, or the backing store is inaccessible. <br /> |

| Returns ||
|---|---|
| `int` | the int value represented by the string associated with key in this preference node, or def if the associated value does not exist or cannot be interpreted as an int. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#putInt(java.lang.String,%20int)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)`

### getLong

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract long getLong (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 `https://developer.android.com/reference/java/lang/Long#parseLong(java.lang.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 `https://developer.android.com/reference/java/lang/NumberFormatException` if the associated value were passed. This
method is intended for use in conjunction with `https://developer.android.com/reference/java/util/prefs/Preferences#putLong(java.lang.String,%20long)`.

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.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key whose associated value is to be returned as a long. <br /> |
| `def` | `long`: the value to be returned in the event that this preference node has no value associated with key or the associated value cannot be interpreted as a long, or the backing store is inaccessible. <br /> |

| Returns ||
|---|---|
| `long` | the long value represented by the string associated with key in this preference node, or def if the associated value does not exist or cannot be interpreted as a long. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#putLong(java.lang.String,%20long)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)`

### importPreferences

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static void importPreferences (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 `https://developer.android.com/reference/java/util/prefs/Preferences#exportNode(java.io.OutputStream)` and `https://developer.android.com/reference/java/util/prefs/Preferences#exportSubtree(java.io.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 `https://developer.android.com/reference/java/util/prefs/Preferences#node(java.lang.String)` and `https://developer.android.com/reference/java/util/prefs/Preferences#put(java.lang.String,%20java.lang.String)`.

<br />

| Parameters ||
|---|---|
| `is` | `InputStream`: the input stream from which to read the XML document. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/IOException` | if reading from the specified input stream results in an IOException. |
| `https://developer.android.com/reference/java/lang/SecurityException` | If a security manager is present and it denies RuntimePermission("preferences"). |
| `https://developer.android.com/reference/java/util/prefs/InvalidPreferencesFormatException` | Data on input stream does not constitute a valid XML document with the mandated document type. |

**See also:**

- `https://developer.android.com/reference/java/lang/RuntimePermission`

### isUserNode

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Returns ||
|---|---|
| `boolean` | true if this preference node is in the user preference tree, false if it's in the system preference tree. <br /> |

### keys

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract 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.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | an array of the keys that have an associated value in this preference node. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if this operation cannot be completed due to a failure in the backing store, or inability to communicate with it. |

### name

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract String name ()
```

Returns this preference node's name, relative to its parent.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | this preference node's name, relative to its parent. <br /> |

### node

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract Preferences node (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).

<br />

| Parameters ||
|---|---|
| `pathName` | `String`: the path name of the preference node to return. <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/prefs/Preferences` | the specified preference node. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if the path name is invalid (i.e., it contains multiple consecutive slash characters, or ends with a slash character and is more than one character long). |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if path name is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#flush()`

### nodeExists

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract boolean nodeExists (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
`https://developer.android.com/reference/java/util/prefs/Preferences#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.

<br />

| Parameters ||
|---|---|
| `pathName` | `String`: the path name of the node whose existence is to be checked. <br /> |

| Returns ||
|---|---|
| `boolean` | true if the specified node exists. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if the path name is invalid (i.e., it contains multiple consecutive slash characters, or ends with a slash character and is more than one character long). |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method and pathName is not the empty string (""). |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if path name is null. |
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if this operation cannot be completed due to a failure in the backing store, or inability to communicate with it. |

### parent

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract Preferences parent ()
```

Returns the parent of this preference node, or null if this is
the root.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/prefs/Preferences` | the parent of this preference node. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |

### put

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void put (String key, 
                String value)
```

Associates the specified value with the specified key in this
preference node.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key with which the specified value is to be associated. <br /> |
| `value` | `String`: value to be associated with the specified key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if key.length() exceeds MAX_KEY_LENGTH or if value.length exceeds MAX_VALUE_LENGTH. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key or value is null. |

### putBoolean

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void putBoolean (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
`https://developer.android.com/reference/java/util/prefs/Preferences#getBoolean(java.lang.String,%20boolean)`.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key with which the string form of value is to be associated. <br /> |
| `value` | `boolean`: value whose string form is to be associated with key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if key.length() exceeds MAX_KEY_LENGTH. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#getBoolean(java.lang.String,%20boolean)`
- `https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)`

### putByteArray

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void putByteArray (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](http://www.ietf.org/rfc/rfc2045.txt), 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
`https://developer.android.com/reference/java/util/prefs/Preferences#getByteArray(java.lang.String,%20byte[])`.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key with which the string form of value is to be associated. <br /> |
| `value` | `byte`: value whose string form is to be associated with key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if key.length() exceeds MAX_KEY_LENGTH or if value.length exceeds MAX_VALUE_LENGTH\*3/4. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key or value is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#getByteArray(java.lang.String,%20byte[])`
- `https://developer.android.com/reference/java/util/prefs/Preferences#get(java.lang.String,%20java.lang.String)`

### putDouble

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void putDouble (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
`https://developer.android.com/reference/java/lang/Double#toString(double)`. This method is intended for use in
conjunction with `https://developer.android.com/reference/java/util/prefs/Preferences#getDouble(java.lang.String,%20double)`.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key with which the string form of value is to be associated. <br /> |
| `value` | `double`: value whose string form is to be associated with key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if key.length() exceeds MAX_KEY_LENGTH. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#getDouble(java.lang.String,%20double)`

### putFloat

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void putFloat (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
`https://developer.android.com/reference/java/lang/Float#toString(float)`. This method is intended for use in
conjunction with `https://developer.android.com/reference/java/util/prefs/Preferences#getFloat(java.lang.String,%20float)`.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key with which the string form of value is to be associated. <br /> |
| `value` | `float`: value whose string form is to be associated with key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if key.length() exceeds MAX_KEY_LENGTH. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#getFloat(java.lang.String,%20float)`

### putInt

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void putInt (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
`https://developer.android.com/reference/java/lang/Integer#toString(int)`. This method is intended for use in
conjunction with `https://developer.android.com/reference/java/util/prefs/Preferences#getInt(java.lang.String,%20int)`.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key with which the string form of value is to be associated. <br /> |
| `value` | `int`: value whose string form is to be associated with key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if key.length() exceeds MAX_KEY_LENGTH. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#getInt(java.lang.String,%20int)`

### putLong

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void putLong (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
`https://developer.android.com/reference/java/lang/Long#toString(long)`. This method is intended for use in
conjunction with `https://developer.android.com/reference/java/util/prefs/Preferences#getLong(java.lang.String,%20long)`.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key with which the string form of value is to be associated. <br /> |
| `value` | `long`: value whose string form is to be associated with key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if key.length() exceeds MAX_KEY_LENGTH. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#getLong(java.lang.String,%20long)`

### remove

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void remove (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.

<br />

| Parameters ||
|---|---|
| `key` | `String`: key whose mapping is to be removed from the preference node. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if key is null. |

### removeNode

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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 `https://developer.android.com/reference/java/util/prefs/Preferences#name()`,
`https://developer.android.com/reference/java/util/prefs/Preferences#absolutePath()`, `https://developer.android.com/reference/java/util/prefs/Preferences#isUserNode()`, `https://developer.android.com/reference/java/util/prefs/Preferences#flush()` or
`https://developer.android.com/reference/java/util/prefs/Preferences#node(java.lang.String)` on the corresponding
Preferences instance will fail with an
IllegalStateException. (The methods defined on `https://developer.android.com/reference/java/lang/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.

<br />

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has already been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if this method is invoked on the root node. |
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if this operation cannot be completed due to a failure in the backing store, or inability to communicate with it. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#flush()`

### removeNodeChangeListener

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void removeNodeChangeListener (NodeChangeListener ncl)
```

Removes the specified NodeChangeListener, so it no longer
receives change events.

<br />

| Parameters ||
|---|---|
| `ncl` | `NodeChangeListener`: The NodeChangeListener to remove. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if ncl was not a registered NodeChangeListener on this node. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#addNodeChangeListener(java.util.prefs.NodeChangeListener)`

### removePreferenceChangeListener

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void removePreferenceChangeListener (PreferenceChangeListener pcl)
```

Removes the specified preference change listener, so it no longer
receives preference change events.

<br />

| Parameters ||
|---|---|
| `pcl` | `PreferenceChangeListener`: The preference change listener to remove. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if pcl was not a registered preference change listener on this node. |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#addPreferenceChangeListener(java.util.prefs.PreferenceChangeListener)`

### sync

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this node (or an ancestor) has been removed with the `https://developer.android.com/reference/java/util/prefs/Preferences#removeNode()` method. |
| `https://developer.android.com/reference/java/util/prefs/BackingStoreException` | if this operation cannot be completed due to a failure in the backing store, or inability to communicate with it. |

**See also:**

- `https://developer.android.com/reference/java/util/prefs/Preferences#flush()`

### systemNodeForPackage

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static Preferences systemNodeForPackage (Class<?> c)
```

**WARNING:** On Android, the Preference nodes
corresponding to the "system" and "user" preferences are stored in sections
of the file system that are inaccessible to apps. Further, allowing apps to set
"system wide" preferences is contrary to android's security model.

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).

<br />

| Parameters ||
|---|---|
| `c` | `Class`: the class for whose package a system preference node is desired. <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/prefs/Preferences` | the system preference node associated with the package of which c is a member. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if c is null. |
| `https://developer.android.com/reference/java/lang/SecurityException` | if a security manager is present and it denies RuntimePermission("preferences"). |

**See also:**

- `https://developer.android.com/reference/java/lang/RuntimePermission`

### systemRoot

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static Preferences systemRoot ()
```

**WARNING:** On Android, the Preference nodes
corresponding to the "system" and "user" preferences are stored in sections
of the file system that are inaccessible to apps. Further, allowing apps to set
"system wide" preferences is contrary to android's security model.

Returns the root preference node for the system.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/prefs/Preferences` | the root preference node for the system. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/SecurityException` | If a security manager is present and it denies RuntimePermission("preferences"). |

**See also:**

- `https://developer.android.com/reference/java/lang/RuntimePermission`

### toString

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract String toString ()
```

Returns a string representation of this preferences node,
as if computed by the expression:(this.isUserNode() ? "User" : "System") + " Preference Node: " + this.absolutePath().

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | a string representation of the object. <br /> |

### userNodeForPackage

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static Preferences userNodeForPackage (Class<?> c)
```

**WARNING:** On Android, the Preference nodes
corresponding to the "system" and "user" preferences are stored in sections
of the file system that are inaccessible to apps. Further, allowing apps to set
"system wide" preferences is contrary to android's security model.

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).

<br />

| Parameters ||
|---|---|
| `c` | `Class`: the class for whose package a user preference node is desired. <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/prefs/Preferences` | the user preference node associated with the package of which c is a member. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if c is null. |
| `https://developer.android.com/reference/java/lang/SecurityException` | if a security manager is present and it denies RuntimePermission("preferences"). |

**See also:**

- `https://developer.android.com/reference/java/lang/RuntimePermission`

### userRoot

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public static Preferences userRoot ()
```

**WARNING:** On Android, the Preference nodes
corresponding to the "system" and "user" preferences are stored in sections
of the file system that are inaccessible to apps. Further, allowing apps to set
"system wide" preferences is contrary to android's security model.

Returns the root preference node for the calling user.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/prefs/Preferences` | the root preference node for the calling user. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/SecurityException` | If a security manager is present and it denies RuntimePermission("preferences"). |

**See also:**

- `https://developer.android.com/reference/java/lang/RuntimePermission`