Package org.apache.commons.collections4.map

Class UnmodifiableMap<K,V>

java.lang.Object

org.apache.commons.collections4.map.AbstractIterableMap<K,V>

org.apache.commons.collections4.map.AbstractMapDecorator<K,V>

org.apache.commons.collections4.map.UnmodifiableMap<K,V>

Type Parameters:

K - the type of the keys in this map

V - the type of the values in this map

All Implemented Interfaces:

Serializable, Map<K,V>, Get<K,V>, IterableGet<K,V>, IterableMap<K,V>, Put<K,V>, Unmodifiable

public final class UnmodifiableMap<K,V>
extends AbstractMapDecorator<K,V>
implements Unmodifiable, Serializable

Decorates another Map to ensure it can't be altered.

This class is Serializable from Commons Collections 3.1.

Attempts to modify it will result in an UnsupportedOperationException.

Since:

3.0

See Also:

• Serialized Form

Nested Class Summary

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

Map.Entry<K extends Object,V extends Object>

Method Summary

Modifier and Type	Method	Description
void	clear()
Set<Map.Entry<K,V>>	entrySet()
Set<K>	keySet()
MapIterator<K,V>	mapIterator()	Obtains a MapIterator over the map.
V	put(K key, V value)	Note that the return type is Object, rather than V as in the Map interface.
void	putAll(Map<? extends K,? extends V> mapToCopy)
V	remove(Object key)
static <K, V> Map<K,V>	unmodifiableMap(Map<? extends K,? extends V> map)	Factory method to create an unmodifiable map.
Collection<V>	values()

Methods inherited from class org.apache.commons.collections4.map.AbstractMapDecorator

containsKey, containsValue, decorated, equals, get, hashCode, isEmpty, size, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Method Details

unmodifiableMap

public static <K,
V> Map<K,V> unmodifiableMap(Map<? extends K,? extends V> map)

Factory method to create an unmodifiable map.

Type Parameters:

K - the key type

V - the value type

Parameters:

map - the map to decorate, must not be null

Returns:

a new unmodifiable map

Throws:

NullPointerException - if map is null

Since:

4.0

clear

public void clear()

Specified by:

clear in interface Map<K,V>

Specified by:

clear in interface Put<K,V>

Overrides:

clear in class AbstractMapDecorator<K,V>

See Also:

• Map.clear()

entrySet

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

Specified by:

entrySet in interface Get<K,V>

Specified by:

entrySet in interface Map<K,V>

Overrides:

entrySet in class AbstractMapDecorator<K,V>

Returns:

a set view of the mappings contained in this map

See Also:

• Map.entrySet()

keySet

public Set<K> keySet()

Specified by:

keySet in interface Get<K,V>

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class AbstractMapDecorator<K,V>

Returns:

a set view of the keys contained in this map

See Also:

• Map.keySet()

mapIterator

public MapIterator<K,V> mapIterator()

Description copied from class: AbstractIterableMap

Obtains a 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.

 IterableMap<String,Integer> map = new HashedMap<String,Integer>();
 MapIterator<String,Integer> it = map.mapIterator();
 while (it.hasNext()) {
   String key = it.next();
   Integer value = it.getValue();
   it.setValue(value + 1);
 }
 

Specified by:

mapIterator in interface IterableGet<K,V>

Overrides:

mapIterator in class AbstractIterableMap<K,V>

Returns:

a map iterator

put

public V put(K key,
 V value)

Description copied from interface: Put

Note that the return type is Object, rather than V as in the Map interface. See the class Javadoc for further info.

Specified by:

put in interface Map<K,V>

Specified by:

put in interface Put<K,V>

Overrides:

put in class AbstractMapDecorator<K,V>

Parameters:

key - key with which the specified value is to be associated

value - value to be associated with the specified key

Returns:

the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key, if the implementation supports null values.)

See Also:

• Map.put(Object, Object)

putAll

public void putAll(Map<? extends K,? extends V> mapToCopy)

Specified by:

putAll in interface Map<K,V>

Specified by:

putAll in interface Put<K,V>

Overrides:

putAll in class AbstractMapDecorator<K,V>

Parameters:

mapToCopy - mappings to be stored in this map

See Also:

• Map.putAll(Map)

remove

public V remove(Object key)

Specified by:

remove in interface Get<K,V>

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractMapDecorator<K,V>

Parameters:

key - key whose mapping is to be removed from the map

Returns:

the previous value associated with key, or null if there was no mapping for key.

See Also:

• Map.remove(Object)

values

public Collection<V> values()

Specified by:

values in interface Get<K,V>

Specified by:

values in interface Map<K,V>

Overrides:

values in class AbstractMapDecorator<K,V>

Returns:

a collection view of the values contained in this map

See Also:

• Map.values()