Package org.apache.commons.collections4.map

Class AbstractHashedMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

org.apache.commons.collections4.map.AbstractHashedMap<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:

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

Direct Known Subclasses:

AbstractLinkedMap, AbstractReferenceMap, CaseInsensitiveMap, HashedMap

public class AbstractHashedMap<K,V>
extends AbstractMap<K,V>
implements IterableMap<K,V>

An abstract implementation of a hash-based map which provides numerous points for subclasses to override.

This class implements all the features necessary for a subclass hash-based map. Key-value entries are stored in instances of the HashEntry class, which can be overridden and replaced. The iterators can similarly be replaced, without the need to replace the KeySet, EntrySet and Values view classes.

Overridable methods are provided to change the default hashing behavior, and to change how entries are added to and removed from the map. Hopefully, all you need for unusual subclasses is here.

NOTE: From Commons Collections 3.1 this class extends AbstractMap. This is to provide backwards compatibility for ReferenceMap between v3.0 and v3.1. This extends clause will be removed in v5.0.

Since:

3.0

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

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

Map.Entry<K,V>

Method Summary

Modifier and Type	Method	Description
void	clear()	Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.
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.
V	get(Object key)	Gets the value mapped to the key specified.
int	hashCode()	Gets the standard Map hashCode.
boolean	isEmpty()	Checks whether the map is currently empty.
Set<K>	keySet()	Gets the keySet view of the map.
MapIterator<K,V>	mapIterator()	Gets an iterator over the map.
V	put(K key, V value)	Puts a key-value mapping into this map.
void	putAll(Map<? extends K,? extends V> map)	Puts all the values from the specified map into this map.
V	remove(Object key)	Removes the specified mapping from this map.
int	size()	Gets the size of the map.
String	toString()	Gets the map as a String.
Collection<V>	values()	Gets the values view of the map.

Methods inherited from class java.lang.Object

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

clear

public void clear()

Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.

Specified by:

clear in interface Map<K,V>

Specified by:

clear in interface Put<K,V>

Overrides:

clear in class AbstractMap<K,V>

See Also:

• Map.clear()

containsKey

public boolean containsKey(Object key)

Checks whether the map contains the specified key.

Specified by:

containsKey in interface Get<K,V>

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractMap<K,V>

Parameters:

key - the key to search for

Returns:

true if the map contains the key

See Also:

• Map.containsKey(Object)

containsValue

public boolean containsValue(Object value)

Checks whether the map contains the specified value.

Specified by:

containsValue in interface Get<K,V>

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class AbstractMap<K,V>

Parameters:

value - the value to search for

Returns:

true if the map contains the value

See Also:

• Map.containsValue(Object)

entrySet

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

Gets the entrySet view of the map. Changes made to the view affect this map. To simply iterate through the entries, use mapIterator().

Specified by:

entrySet in interface Get<K,V>

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in class AbstractMap<K,V>

Returns:

the entrySet view

See Also:

• Map.entrySet()

equals

public boolean equals(Object obj)

Compares this map with another.

Specified by:

equals in interface Map<K,V>

Overrides:

equals in class AbstractMap<K,V>

Parameters:

obj - the object to compare to

Returns:

true if equal

get

public V get(Object key)

Gets the value mapped to the key specified.

Specified by:

get in interface Get<K,V>

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMap<K,V>

Parameters:

key - the key

Returns:

the mapped value, null if no match

See Also:

• Map.get(Object)

hashCode

public int hashCode()

Gets the standard Map hashCode.

Specified by:

hashCode in interface Map<K,V>

Overrides:

hashCode in class AbstractMap<K,V>

Returns:

the hash code defined in the Map interface

isEmpty

public boolean isEmpty()

Checks whether the map is currently empty.

Specified by:

isEmpty in interface Get<K,V>

Specified by:

isEmpty in interface Map<K,V>

Overrides:

isEmpty in class AbstractMap<K,V>

Returns:

true if the map is currently size zero

See Also:

• Map.isEmpty()

keySet

public Set<K> keySet()

Gets the keySet view of the map. Changes made to the view affect this map. To simply iterate through the keys, use mapIterator().

Specified by:

keySet in interface Get<K,V>

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class AbstractMap<K,V>

Returns:

the keySet view

See Also:

• Map.keySet()

mapIterator

public MapIterator<K,V> mapIterator()

Gets an iterator over the map. Changes made to the iterator affect this map.

A MapIterator returns the keys in the map. It also provides convenient methods to get the key and value, and set the value. It avoids the need to create an entrySet/keySet/values object. It also avoids creating the Map.Entry object.

Specified by:

mapIterator in interface IterableGet<K,V>

Returns:

the map iterator

put

public V put(K key,
 V value)

Puts a key-value mapping into this map.

Specified by:

put in interface Map<K,V>

Specified by:

put in interface Put<K,V>

Overrides:

put in class AbstractMap<K,V>

Parameters:

key - the key to add

value - the value to add

Returns:

the value previously mapped to this key, null if none

See Also:

• Map.put(Object, Object)

putAll

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

Puts all the values from the specified map into this map.

This implementation iterates around the specified map and uses put(Object, Object).

Specified by:

putAll in interface Map<K,V>

Specified by:

putAll in interface Put<K,V>

Overrides:

putAll in class AbstractMap<K,V>

Parameters:

map - the map to add

Throws:

NullPointerException - if the map is null

See Also:

• Map.putAll(Map)

remove

public V remove(Object key)

Removes the specified mapping from this map.

Specified by:

remove in interface Get<K,V>

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractMap<K,V>

Parameters:

key - the mapping to remove

Returns:

the value mapped to the removed key, null if key not in map

See Also:

• Map.remove(Object)

size

public int size()

Gets the size of the map.

Specified by:

size in interface Get<K,V>

Specified by:

size in interface Map<K,V>

Overrides:

size in class AbstractMap<K,V>

Returns:

the size

See Also:

• Map.size()

toString

public String toString()

Gets the map as a String.

Overrides:

toString in class AbstractMap<K,V>

Returns:

a string version of the map

values

public Collection<V> values()

Gets the values view of the map. Changes made to the view affect this map. To simply iterate through the values, use mapIterator().

Specified by:

values in interface Get<K,V>

Specified by:

values in interface Map<K,V>

Overrides:

values in class AbstractMap<K,V>

Returns:

the values view

See Also:

• Map.values()