Top Description Constructors Methods
java.util

public abstract Class Dictionary<K, V>

extends Object
Class Inheritance
Known Direct Subclasses
java.util.Hashtable
Type Parameters
<K>
the type of keys
<V>
the type of mapped values
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This class is obsolete.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.

Since
1.0
See Also
java.util.Map, java.lang.Object#equals(java.lang.Object), java.lang.Object#hashCode(), java.util.Hashtable

Constructor Summary

AccessConstructor and Description
public
Dictionary()

Sole constructor.

Method Summary

Modifier and TypeMethod and Description
public abstract Enumeration<V>

Returns:

an enumeration of the values in this dictionary.
elements()

Returns an enumeration of the values in this dictionary.

public abstract V

Returns:

the value to which the key is mapped in this dictionary;
get(Object
a key in this dictionary. null if the key is not mapped to any value in this dictionary.
key)

Returns the value to which the key is mapped in this dictionary.

public abstract boolean

Returns:

true if this dictionary maps no keys to values; false otherwise.
isEmpty()

Tests if this dictionary maps no keys to value.

public abstract Enumeration<K>

Returns:

an enumeration of the keys in this dictionary.
keys()

Returns an enumeration of the keys in this dictionary.

public abstract V

Returns:

the previous value to which the key was mapped in this dictionary, or null if the key did not have a previous mapping.
put(K
the hashtable key.
key, V
the value.
value)

Maps the specified key to the specified value in this dictionary.

public abstract V

Returns:

the value to which the key had been mapped in this dictionary, or null if the key did not have a mapping.
remove(Object
the key that needs to be removed.
key)

Removes the key (and its corresponding value) from this dictionary.

public abstract int

Returns:

the number of keys in this dictionary.
size()

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

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Constructor Detail

Dictionaryback to summary
public Dictionary()

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

Method Detail

elementsback to summary
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
java.util.Dictionary#keys(), java.util.Enumeration
getback to summary
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;

Exceptions
NullPointerException:
if the key is null.
See Also
java.util.Dictionary#put(java.lang.Object, java.lang.Object)
isEmptyback to summary
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.

keysback to summary
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
java.util.Dictionary#elements(), java.util.Enumeration
putback to summary
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.

Exceptions
NullPointerException:
if the key or value is null.
See Also
java.lang.Object#equals(java.lang.Object), java.util.Dictionary#get(java.lang.Object)
removeback to summary
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.

Exceptions
NullPointerException:
if key is null.
sizeback to summary
public abstract int size()

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

Returns:int

the number of keys in this dictionary.