org.apache.commons.collections.map

Class AbstractHashedMap

java.lang.Object

java.util.AbstractMap

org.apache.commons.collections.map.AbstractHashedMap

All Implemented Interfaces:

java.util.Map, IterableMap

Direct Known Subclasses:

AbstractLinkedMap, AbstractReferenceMap, CaseInsensitiveMap, HashedMap, IdentityMap

public class AbstractHashedMap
extends java.util.AbstractMap
implements IterableMap

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 behaviour, 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 v4.0.

Since:

Commons Collections 3.0

Nested Class Summary

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

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

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

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

Method Summary

Modifier and Type	Method and Description
void	clear() Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.
boolean	containsKey(java.lang.Object key) Checks whether the map contains the specified key.
boolean	containsValue(java.lang.Object value) Checks whether the map contains the specified value.
java.util.Set	entrySet() Gets the entrySet view of the map.
boolean	equals(java.lang.Object obj) Compares this map with another.
java.lang.Object	get(java.lang.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.
java.util.Set	keySet() Gets the keySet view of the map.
MapIterator	mapIterator() Gets an iterator over the map.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Puts a key-value mapping into this map.
void	putAll(java.util.Map map) Puts all the values from the specified map into this map.
java.lang.Object	remove(java.lang.Object key) Removes the specified mapping from this map.
int	size() Gets the size of the map.
java.lang.String	toString() Gets the map as a String.
java.util.Collection	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 Detail

get

public java.lang.Object get(java.lang.Object key)

Gets the value mapped to the key specified.

Specified by:

get in interface java.util.Map

Overrides:

get in class java.util.AbstractMap

Parameters:

key - the key

Returns:

the mapped value, null if no match

size

public int size()

Gets the size of the map.

Specified by:

size in interface java.util.Map

Overrides:

size in class java.util.AbstractMap

Returns:

the size

isEmpty

public boolean isEmpty()

Checks whether the map is currently empty.

Specified by:

isEmpty in interface java.util.Map

Overrides:

isEmpty in class java.util.AbstractMap

Returns:

true if the map is currently size zero

containsKey

public boolean containsKey(java.lang.Object key)

Checks whether the map contains the specified key.

Specified by:

containsKey in interface java.util.Map

Overrides:

containsKey in class java.util.AbstractMap

Parameters:

key - the key to search for

Returns:

true if the map contains the key

containsValue

public boolean containsValue(java.lang.Object value)

Checks whether the map contains the specified value.

Specified by:

containsValue in interface java.util.Map

Overrides:

containsValue in class java.util.AbstractMap

Parameters:

value - the value to search for

Returns:

true if the map contains the value

put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object value)

Puts a key-value mapping into this map.

Specified by:

put in interface java.util.Map

Overrides:

put in class java.util.AbstractMap

Parameters:

key - the key to add

value - the value to add

Returns:

the value previously mapped to this key, null if none

putAll

public void putAll(java.util.Map 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 java.util.Map

Overrides:

putAll in class java.util.AbstractMap

Parameters:

map - the map to add

Throws:

java.lang.NullPointerException - if the map is null

remove

public java.lang.Object remove(java.lang.Object key)

Removes the specified mapping from this map.

Specified by:

remove in interface java.util.Map

Overrides:

remove in class java.util.AbstractMap

Parameters:

key - the mapping to remove

Returns:

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

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 java.util.Map

Overrides:

clear in class java.util.AbstractMap

mapIterator

public MapIterator 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 IterableMap

Returns:

the map iterator

entrySet

public java.util.Set 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 java.util.Map

Specified by:

entrySet in class java.util.AbstractMap

Returns:

the entrySet view

keySet

public java.util.Set 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 java.util.Map

Overrides:

keySet in class java.util.AbstractMap

Returns:

the keySet view

values

public java.util.Collection 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 java.util.Map

Overrides:

values in class java.util.AbstractMap

Returns:

the values view

equals

public boolean equals(java.lang.Object obj)

Compares this map with another.

Specified by:

equals in interface java.util.Map

Overrides:

equals in class java.util.AbstractMap

Parameters:

obj - the object to compare to

Returns:

true if equal

hashCode

public int hashCode()

Gets the standard Map hashCode.

Specified by:

hashCode in interface java.util.Map

Overrides:

hashCode in class java.util.AbstractMap

Returns:

the hash code defined in the Map interface

toString

public java.lang.String toString()

Gets the map as a String.

Overrides:

toString in class java.util.AbstractMap

Returns:

a string version of the map