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java.lang.Objectorg.apache.commons.collections4.map.SingletonMap<K,V>
public class SingletonMap<K,V>
A Map
implementation that holds a single item and is fixed size.
The single key/value pair is specified at creation.
The map is fixed size so any action that would change the size is disallowed.
However, the put
or setValue
methods can change
the value associated with the key.
If trying to remove or clear the map, an UnsupportedOperationException is thrown. If trying to put a new mapping into the map, an IllegalArgumentException is thrown. The put method will only suceed if the key specified is the same as the singleton key.
The key and value can be obtained by:
MapIterator
, see mapIterator()
KeyValue
interface (just cast - no object creation)
Nested Class Summary |
---|
Nested classes/interfaces inherited from interface java.util.Map |
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Map.Entry<K,V> |
Nested classes/interfaces inherited from interface java.util.Map |
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Map.Entry<K,V> |
Constructor Summary | |
---|---|
SingletonMap()
Constructor that creates a map of null to null . |
|
SingletonMap(KeyValue<K,V> keyValue)
Constructor specifying the key and value as a KeyValue . |
|
SingletonMap(K key,
V value)
Constructor specifying the key and value. |
|
SingletonMap(Map.Entry<K,V> mapEntry)
Constructor specifying the key and value as a MapEntry . |
|
SingletonMap(Map<K,V> map)
Constructor copying elements from another map. |
Method Summary | |
---|---|
void |
clear()
Unsupported operation. |
SingletonMap<K,V> |
clone()
Clones the map without cloning the key or value. |
boolean |
containsKey(Object key)
Checks whether the map contains the specified key. |
boolean |
containsValue(Object value)
Checks whether the map contains the specified value. |
Set<Map.Entry<K,V>> |
entrySet()
Gets the entrySet view of the map. |
boolean |
equals(Object obj)
Compares this map with another. |
K |
firstKey()
Gets the first (and only) key in the map. |
V |
get(Object key)
Gets the value mapped to the key specified. |
K |
getKey()
Gets the key. |
V |
getValue()
Gets the value. |
int |
hashCode()
Gets the standard Map hashCode. |
boolean |
isEmpty()
Checks whether the map is currently empty, which it never is. |
protected boolean |
isEqualKey(Object key)
Compares the specified key to the stored key. |
protected boolean |
isEqualValue(Object value)
Compares the specified value to the stored value. |
boolean |
isFull()
Is the map currently full, always true. |
Set<K> |
keySet()
Gets the unmodifiable keySet view of the map. |
K |
lastKey()
Gets the last (and only) key in the map. |
OrderedMapIterator<K,V> |
mapIterator()
Obtains a MapIterator over the map. |
int |
maxSize()
Gets the maximum size of the map, always 1. |
K |
nextKey(K key)
Gets the next key after the key specified, always null. |
K |
previousKey(K key)
Gets the previous key before the key specified, always null. |
V |
put(K key,
V value)
Puts a key-value mapping into this map where the key must match the existing key. |
void |
putAll(Map<? extends K,? extends V> map)
Puts the values from the specified map into this map. |
V |
remove(Object key)
Unsupported operation. |
V |
setValue(V value)
Sets the value. |
int |
size()
Gets the size of the map, always 1. |
String |
toString()
Gets the map as a String. |
Collection<V> |
values()
Gets the unmodifiable values view of the map. |
Methods inherited from class java.lang.Object |
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finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
public SingletonMap()
null
to null
.
public SingletonMap(K key, V value)
key
- the key to usevalue
- the value to usepublic SingletonMap(KeyValue<K,V> keyValue)
KeyValue
.
keyValue
- the key value pair to usepublic SingletonMap(Map.Entry<K,V> mapEntry)
MapEntry
.
mapEntry
- the mapEntry to usepublic SingletonMap(Map<K,V> map)
map
- the map to copy, must be size 1
NullPointerException
- if the map is null
IllegalArgumentException
- if the size is not 1Method Detail |
---|
public K getKey()
getKey
in interface KeyValue<K,V>
public V getValue()
getValue
in interface KeyValue<K,V>
public V setValue(V value)
value
- the new value to set
public boolean isFull()
isFull
in interface BoundedMap<K,V>
public int maxSize()
maxSize
in interface BoundedMap<K,V>
public V get(Object key)
get
in interface Map<K,V>
get
in interface Get<K,V>
key
- the key
Map.get(Object)
public int size()
size
in interface Map<K,V>
size
in interface Get<K,V>
Map.size()
public boolean isEmpty()
isEmpty
in interface Map<K,V>
isEmpty
in interface Get<K,V>
Map.isEmpty()
public boolean containsKey(Object key)
containsKey
in interface Map<K,V>
containsKey
in interface Get<K,V>
key
- the key to search for
Map.containsKey(Object)
public boolean containsValue(Object value)
containsValue
in interface Map<K,V>
containsValue
in interface Get<K,V>
value
- the value to search for
Map.containsValue(Object)
public V put(K key, V value)
An IllegalArgumentException is thrown if the key does not match as the map is fixed size.
put
in interface Map<K,V>
put
in interface Put<K,V>
key
- the key to set, must be the key of the mapvalue
- the value to set
IllegalArgumentException
- if the key does not matchMap.put(Object, Object)
public void putAll(Map<? extends K,? extends V> map)
The map must be of size 0 or size 1. If it is size 1, the key must match the key of this map otherwise an IllegalArgumentException is thrown.
putAll
in interface Map<K,V>
putAll
in interface Put<K,V>
map
- the map to add, must be size 0 or 1, and the key must match
NullPointerException
- if the map is null
IllegalArgumentException
- if the key does not matchMap.putAll(Map)
public V remove(Object key)
remove
in interface Map<K,V>
remove
in interface Get<K,V>
key
- the mapping to remove
UnsupportedOperationException
- alwaysMap.remove(Object)
public void clear()
clear
in interface Map<K,V>
clear
in interface Put<K,V>
Map.clear()
public Set<Map.Entry<K,V>> entrySet()
setValue
affect this map.
To simply iterate through the entries, use mapIterator()
.
entrySet
in interface Map<K,V>
entrySet
in interface Get<K,V>
Map.entrySet()
public Set<K> keySet()
mapIterator()
.
keySet
in interface Map<K,V>
keySet
in interface Get<K,V>
Map.keySet()
public Collection<V> values()
mapIterator()
.
values
in interface Map<K,V>
values
in interface Get<K,V>
Map.values()
public OrderedMapIterator<K,V> mapIterator()
MapIterator
over the map.
A map iterator is an efficient way of iterating over maps. There is no need to access the entry set or use Map Entry objects.
IterableMapmap = new HashedMap (); MapIterator it = map.mapIterator(); while (it.hasNext()) { String key = it.next(); Integer value = it.getValue(); it.setValue(value + 1); }
mapIterator
in interface IterableGet<K,V>
mapIterator
in interface OrderedMap<K,V>
public K firstKey()
firstKey
in interface OrderedMap<K,V>
public K lastKey()
lastKey
in interface OrderedMap<K,V>
public K nextKey(K key)
nextKey
in interface OrderedMap<K,V>
key
- the next key
public K previousKey(K key)
previousKey
in interface OrderedMap<K,V>
key
- the next key
protected boolean isEqualKey(Object key)
key
- the key to compare
protected boolean isEqualValue(Object value)
value
- the value to compare
public SingletonMap<K,V> clone()
clone
in class Object
public boolean equals(Object obj)
equals
in interface Map<K,V>
equals
in class Object
obj
- the object to compare to
public int hashCode()
hashCode
in interface Map<K,V>
hashCode
in class Object
public String toString()
toString
in class Object
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