edu.tum.cs.commons.collections
Class ArrayBackedMap<K,V>

java.lang.Object
  edu.tum.cs.commons.collections.ArrayBackedMap<K,V>

All Implemented Interfaces:

Map<K,V>

Direct Known Subclasses:

ArrayBackedStringMap

public class ArrayBackedMap<K,V>
extends Object
implements Map<K,V>

A map implementation based on unsorted arrays. This is by far more memory efficient than the usual map implementations and has reasonable performance for small maps. Note that this map violates the map interface by just returning copies for the set accessor methods (entrySet(), values(), keySet()), i.e. they are not backed by the map.

Implementation hints:

• Nearly all operations require a full traversal of the array (resp. PairList).
• Iteration is performed backwards, to avoid frequent calls to size() method. This also gives more efficient access to recently added elements.
• This class is prepared to support subclasses with more specific keys with more efficient key handling. Thus all keys inserted are preprocessed and comparison of keys can be overwritten.

Version:

$Rev: 28496 $

Author:

hummelb, $Author: deissenb $

Rating:

GREEN Hash: FD4724FBA572E6336FD0EE8890B9CD58

Nested Class Summary

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

Map.Entry<K,V>

Constructor Summary

ArrayBackedMap()
Constructs a new map with an initial capacity of 4.

ArrayBackedMap(int initialCapacity)
Constructor.

Method Summary

protected boolean	areEqual(K key1, K key2) Template method for comparing two keys for equality.
void	clear()
boolean	containsKey(Object key)
boolean	containsValue(Object value)
Set<Map.Entry<K,V>>	entrySet()
V	get(Object key)
protected K	internKey(Object key) Template method for calculating an internal key representation.
boolean	isEmpty()
Set<K>	keySet()
V	put(K key, V value)
void	putAll(Map<? extends K,? extends V> m)
V	remove(Object key)
int	size()
Collection<V>	values()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode

Constructor Detail

ArrayBackedMap

public ArrayBackedMap()

Constructs a new map with an initial capacity of 4.

ArrayBackedMap

public ArrayBackedMap(int initialCapacity)

Constructor.

Method Detail

clear

public void clear()

Specified by:

clear in interface Map<K,V>

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map<K,V>

internKey

protected K internKey(Object key)
               throws ClassCastException

Template method for calculating an internal key representation. The default implementation just performs a cast. This method may throw a class cast exception if the provided key is not an instance of the key type.

Throws:

ClassCastException - if the provided key is not of a suitable class.

areEqual

protected boolean areEqual(K key1,
                           K key2)

Template method for comparing two keys for equality.

get

public V get(Object key)

Specified by:

get in interface Map<K,V>

put

public V put(K key,
             V value)

Specified by:

put in interface Map<K,V>

remove

public V remove(Object key)

Specified by:

remove in interface Map<K,V>

containsValue

public boolean containsValue(Object value)

Specified by:

containsValue in interface Map<K,V>

entrySet

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

Specified by:

entrySet in interface Map<K,V>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map<K,V>

keySet

public Set<K> keySet()

Specified by:

keySet in interface Map<K,V>

putAll

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

Specified by:

putAll in interface Map<K,V>

size

public int size()

Specified by:

size in interface Map<K,V>

values

public Collection<V> values()

Specified by:

values in interface Map<K,V>