Added in API level 1

Summary: Ctors | Methods | Inherited Methods

Dictionary

public abstract class Dictionary
extends Object

java.lang.Object
↳	java.util.Dictionary<K, V>

Known direct subclasses

Hashtable<K, V>

Hashtable<K, V> This class implements a hash table, which maps keys to values.

Known indirect subclasses

AuthProvider, Properties, Provider

AuthProvider	Legacy security code; do not use.
Properties	The `Properties` class represents a persistent set of properties.
Provider	This class represents a "provider" for the Java Security API, where a provider implements some or all parts of Java Security.

The Dictionary class is the abstract parent of any class, such as Hashtable, which maps keys to values. Every key and every value is an object. In any one Dictionary object, every key is associated with at most one value. Given a Dictionary and a key, the associated element can be looked up. Any non-null object can be used as a key and as a value.

As a rule, the equals method should be used by implementations of this class to decide if two keys are the same.

NOTE: This class is obsolete. New implementations should implement the Map interface, rather than extending this class.

See also:

Summary

Public constructors
`Dictionary()` Sole constructor.

Public methods
`abstract Enumeration<V>`	`elements()` Returns an enumeration of the values in this dictionary.
`abstract V`	`get(Object key)` Returns the value to which the key is mapped in this dictionary.
`abstract boolean`	`isEmpty()` Tests if this dictionary maps no keys to value.
`abstract Enumeration<K>`	`keys()` Returns an enumeration of the keys in this dictionary.
`abstract V`	`put(K key, V value)` Maps the specified `key` to the specified `value` in this dictionary.
`abstract V`	`remove(Object key)` Removes the `key` (and its corresponding `value`) from this dictionary.
`abstract int`	`size()` Returns the number of entries (distinct keys) in this dictionary.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(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`	`wait(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`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public constructors

Dictionary

Added in API level 1

public Dictionary ()

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

Public methods

elements

Added in API level 1

public abstract Enumeration<V> elements ()

Returns an enumeration of the values in this dictionary. The general contract for the elements method is that an Enumeration is returned that will generate all the elements contained in entries in this dictionary.

Returns
`Enumeration<V>`	an enumeration of the values in this dictionary.

See also:

keys()
Enumeration

get

Added in API level 1

public abstract V get (Object key)

Returns the value to which the key is mapped in this dictionary. The general contract for the isEmpty method is that if this dictionary contains an entry for the specified key, the associated value is returned; otherwise, null is returned.

Parameters
`key`	`Object`: a key in this dictionary. `null` if the key is not mapped to any value in this dictionary.

Returns
`V`	the value to which the key is mapped in this dictionary;

Throws
`NullPointerException`	if the `key` is `null`.

See also:

put(java.lang.Object, java.lang.Object)

isEmpty

Added in API level 1

public abstract boolean isEmpty ()

Tests if this dictionary maps no keys to value. The general contract for the isEmpty method is that the result is true if and only if this dictionary contains no entries.

Returns
`boolean`	`true` if this dictionary maps no keys to values; `false` otherwise.

keys

Added in API level 1

public abstract Enumeration<K> keys ()

Returns an enumeration of the keys in this dictionary. The general contract for the keys method is that an Enumeration object is returned that will generate all the keys for which this dictionary contains entries.

Returns
`Enumeration<K>`	an enumeration of the keys in this dictionary.

See also:

elements()
Enumeration

put

Added in API level 1

public abstract V put (K key, 
                V value)

Maps the specified key to the specified value in this dictionary. Neither the key nor the value can be null.

If this dictionary already contains an entry for the specified key, the value already in this dictionary for that key is returned, after modifying the entry to contain the new element.

If this dictionary does not already have an entry for the specified key, an entry is created for the specified key and value, and null is returned.

The value can be retrieved by calling the get method with a key that is equal to the original key.

Parameters
`key`	`K`: the hashtable key.
`value`	`V`: the value.

Returns
`V`	the previous value to which the `key` was mapped in this dictionary, or `null` if the key did not have a previous mapping.

Throws
`NullPointerException`	if the `key` or `value` is `null`.

See also:

remove

Added in API level 1

public abstract V remove (Object key)

Removes the key (and its corresponding value) from this dictionary. This method does nothing if the key is not in this dictionary.

Parameters
`key`	`Object`: the key that needs to be removed.

Returns
`V`	the value to which the `key` had been mapped in this dictionary, or `null` if the key did not have a mapping.

Throws
`NullPointerException`	if `key` is `null`.

size

Added in API level 1

public abstract int size ()

Returns the number of entries (distinct keys) in this dictionary.

Returns
`int`	the number of keys in this dictionary.