com.twelvemonkeys.util
Class NullMap<K,V>

java.lang.Object
  com.twelvemonkeys.util.NullMap<K,V>

All Implemented Interfaces:

Serializable, Map<K,V>

public final class NullMap<K,V>
extends Object
implements Map<K,V>, Serializable

An (immutable) empty Map, that supports all Map operations without throwing exceptions (in contrast to Collections.EMPTY_MAP that will throw exceptions on put/remove).

NOTE: This is not a general purpose Map implementation, as the put and putAll methods will not modify the map. Instances of this class will always be an empty map.

Version:

$Id: com/twelvemonkeys/util/NullMap.java#2 $

Author:

Harald Kuhr

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Constructor Summary

NullMap()

Method Summary

void	clear()
boolean	containsKey(Object pKey)
boolean	containsValue(Object pValue)
Set<Map.Entry<K,V>>	entrySet()
boolean	equals(Object pOther) Tests the given object for equality (wether it is also an empty Map).
V	get(Object pKey)
int	hashCode() Returns the hashCode of the empty map, 0.
boolean	isEmpty()
Set<K>	keySet()
V	put(Object pKey, Object pValue)
void	putAll(Map pMap)
V	remove(Object pKey)
int	size()
Collection<V>	values()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NullMap

public NullMap()

Method Detail

size

public final int size()

Specified by:

size in interface Map<K,V>

clear

public final void clear()

Specified by:

clear in interface Map<K,V>

isEmpty

public final boolean isEmpty()

Specified by:

isEmpty in interface Map<K,V>

containsKey

public final boolean containsKey(Object pKey)

Specified by:

containsKey in interface Map<K,V>

containsValue

public final boolean containsValue(Object pValue)

Specified by:

containsValue in interface Map<K,V>

values

public final Collection<V> values()

Specified by:

values in interface Map<K,V>

putAll

public final void putAll(Map pMap)

Specified by:

putAll in interface Map<K,V>

entrySet

public final Set<Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface Map<K,V>

keySet

public final Set<K> keySet()

Specified by:

keySet in interface Map<K,V>

get

public final V get(Object pKey)

Specified by:

get in interface Map<K,V>

remove

public final V remove(Object pKey)

Specified by:

remove in interface Map<K,V>

put

public final V put(Object pKey,
                   Object pValue)

Specified by:

put in interface Map<K,V>

equals

public boolean equals(Object pOther)

Tests the given object for equality (wether it is also an empty Map). This is consistent with the standard Map implementations of the Java Collections Framework.

Specified by:

equals in interface Map<K,V>

Overrides:

equals in class Object

Parameters:

pOther - the object to compare with

Returns:

true if pOther is an empty Map, otherwise false

hashCode

public int hashCode()

Returns the hashCode of the empty map, 0. This is consistent with the standard Map implementations of the Java Collections Framework.

Specified by:

hashCode in interface Map<K,V>

Overrides:

hashCode in class Object

Returns:

0, always