com.twelvemonkeys.util

Class NullMap<K,V>

java.lang.Object

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

All Implemented Interfaces:

java.io.Serializable, java.util.Map<K,V>

public final class NullMap<K,V>
extends java.lang.Object
implements java.util.Map<K,V>, java.io.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

java.util.Map.Entry<K,V>

Constructor Summary

Constructors

Constructor and Description
NullMap()

Method Summary

Methods

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

clear

public final void clear()

Specified by:

clear in interface java.util.Map<K,V>

isEmpty

public final boolean isEmpty()

Specified by:

isEmpty in interface java.util.Map<K,V>

containsKey

public final boolean containsKey(java.lang.Object pKey)

Specified by:

containsKey in interface java.util.Map<K,V>

containsValue

public final boolean containsValue(java.lang.Object pValue)

Specified by:

containsValue in interface java.util.Map<K,V>

values

public final java.util.Collection<V> values()

Specified by:

values in interface java.util.Map<K,V>

putAll

public final void putAll(java.util.Map pMap)

Specified by:

putAll in interface java.util.Map<K,V>

entrySet

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

Specified by:

entrySet in interface java.util.Map<K,V>

keySet

public final java.util.Set<K> keySet()

Specified by:

keySet in interface java.util.Map<K,V>

get

public final V get(java.lang.Object pKey)

Specified by:

get in interface java.util.Map<K,V>

remove

public final V remove(java.lang.Object pKey)

Specified by:

remove in interface java.util.Map<K,V>

put

public final V put(java.lang.Object pKey,
    java.lang.Object pValue)

Specified by:

put in interface java.util.Map<K,V>

equals

public boolean equals(java.lang.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 java.util.Map<K,V>

Overrides:

equals in class java.lang.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 java.util.Map<K,V>

Overrides:

hashCode in class java.lang.Object

Returns:

0, always