java.util

Class Dictionary<K,V>

public abstract class Dictionary<K,V> extends Object

A Dictionary maps keys to values; how it does that is implementation-specific. This is an abstract class which has really gone by the wayside. People at Javasoft are probably embarrassed by it. At this point, it might as well be an interface rather than a class, but it remains this poor, laughable skeleton for the sake of backwards compatibility. At any rate, this was what came before the {@link Map} interface in the Collections framework.

Since: 1.0

See Also: Map Hashtable

UNKNOWN: updated to 1.4

Constructor Summary
	Dictionary() Sole constructor (often called implicitly).

Method Summary
abstract Enumeration<V>	elements() Returns an Enumeration of the values in this Dictionary.
abstract V	get(Object key) Returns the value associated with the supplied key, or null if no such value exists.
abstract boolean	isEmpty() Returns true when there are no elements in this Dictionary.
abstract Enumeration<K>	keys() Returns an Enumeration of the keys in this Dictionary
abstract V	put(K key, V value) Inserts a new value into this Dictionary, located by the supplied key.
abstract V	remove(Object key) Removes from the Dictionary the value located by the given key.
abstract int	size() Returns the number of values currently in this Dictionary.

Constructor Detail

Dictionary

public Dictionary()

Sole constructor (often called implicitly).

Method Detail

elements

public abstract Enumeration<V> elements()

Returns an Enumeration of the values in this Dictionary.

Returns: an Enumeration of the values

get

public abstract V get(Object key)

Returns the value associated with the supplied key, or null if no such value exists. Since Dictionaries are not allowed null keys or elements, a null result always means the key is not present.

Parameters: key the key to use to fetch the value

Returns: the mapped value

Throws: NullPointerException if key is null

isEmpty

public abstract boolean isEmpty()

Returns true when there are no elements in this Dictionary.

Returns: size() == 0

keys

public abstract Enumeration<K> keys()

Returns an Enumeration of the keys in this Dictionary

Returns: an Enumeration of the keys

put

public abstract V put(K key, V value)

Inserts a new value into this Dictionary, located by the supplied key. Dictionary does not support null keys or values, so a null return can safely be interpreted as adding a new key.

Parameters: key the key which locates the value value the value to put into the Dictionary

Returns: the previous value of the key, or null if there was none

Throws: NullPointerException if key or value is null

remove

public abstract V remove(Object key)

Removes from the Dictionary the value located by the given key. A null return safely means that the key was not mapped in the Dictionary.

Parameters: key the key used to locate the value to be removed

Returns: the value associated with the removed key

Throws: NullPointerException if key is null

size

public abstract int size()

Returns the number of values currently in this Dictionary.

Returns: the number of keys in the Dictionary