Class java.util.Dictionary
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Class java.util.Dictionary
java.lang.Object
|
+----java.util.Dictionary
public abstract class Dictionary
extends Object
The Dictionary class is the abstract parent of any
class, such as Hashtable, which maps keys to values.
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.
See Also:
equals, hashCode, Hashtable
Dictionary()
elements()
Returns an enumeration of the values in this dictionary.
get(Object)
Returns the value to which the key is mapped in this dictionary.
isEmpty()
Tests if this dictionary maps no keys to value.
keys()
Returns an enumeration of the keys in this dictionary.
put(Object, Object)
Maps the specified key to the specified
value in this dictionary.
remove(Object)
Removes the key (and its corresponding
value) from this dictionary.
size()
Returns the number of keys in this dictionary.
Dictionary
public Dictionary()
size
public abstract int size()
Returns the number of keys in this dictionary.
Returns:
the number of keys in this dictionary.
isEmpty
public abstract boolean isEmpty()
Tests if this dictionary maps no keys to value.
Returns:
true if this dictionary maps no keys to values;
false otherwise.
keys
public abstract Enumeration keys()
Returns an enumeration of the keys in this dictionary.
Returns:
an enumeration of the keys in this dictionary.
See Also:
elements, Enumeration
elements
public abstract Enumeration elements()
Returns an enumeration of the values in this dictionary.
the Enumeration methods on the returned object to fetch the elements
sequentially.
Returns:
an enumeration of the values in this dictionary.
See Also:
keys, Enumeration
get
public abstract Object get(Object key)
Returns the value to which the key is mapped in this dictionary.
Parameters:
key - a key in this dictionary.
null if the key is not mapped to any value in
this dictionary.
Returns:
the value to which the key is mapped in this dictionary;
See Also:
put
put
public abstract Object put(Object key,
Object value)
Maps the specified key to the specified
value in this dictionary. Neither the key nor the
value can be null.
The value can be retrieved by calling the
get method with a key that is equal to
the original key.
Parameters:
key - the hashtable key.
value - the value.
Returns:
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:
equals, get
remove
public abstract Object 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 - the key that needs to be removed.
Returns:
the value to which the key had been mapped in this
dictionary, or null if the key did not have a
mapping.
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