ariba.util.core
Class MemoryOptimizedMap<K,V>

java.lang.Object
  ariba.util.core.MemoryOptimizedMap<K,V>

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>

public abstract class MemoryOptimizedMap<K,V>
extends Object
implements Map<K,V>, Cloneable, Serializable

This is a map implementation that is very memory efficient for very small maps. It is based on the observation that for very small maps, the general overhead can accumulate, especially if you have a lot of them. For example, this is the memory usage for some ways to store 2 pointers: Object w/ 2 members: 16 bytes Object[2] : 24 bytes Object w member which is an Object[2]: 40 bytes This map implementation uses a very simple linear search, which should not be an issue for the sizes in this map. The map switches over to a HashMap if it becomes too large. It behaves exactly like a regular map. Note that 2 methods in the EntrySet are not implemented, however those should be rarely used. Generally one needs to be very aware of how these maps are being used, so this class needs to be very carefully applied. Normally if you feel like you should use this class, you probably did something overall wrong, and should redesign your algorithms ...

See Also:

Serialized Form

Constructor Summary

MemoryOptimizedMap()

Method Summary

void	clear()
Object	clone()
boolean	containsKey(Object key)
boolean	containsValue(Object value)
static Map	deepOptimize(Map tab)
Set<Map.Entry<K,V>>	entrySet() Returns a collection view of the mappings contained in this map.
V	get(Object key)
static <K,V> Map<K,V>	getOptimizedMap(int size)
boolean	isEmpty()
Set<K>	keySet() Returns a set view of the keys contained in this map.
static <K,V> Map<K,V>	optimize(Map<K,V> tab)
static <K,V> Map<K,V>	optimize(Map<K,V> tab, boolean growOnly)
static void	optimizeInPlace(Map s)
V	put(K key, V value)
void	putAll(Map<? extends K,? extends V> t)
V	remove(Object key)
int	size()
Collection<V>	values() Returns a collection view of the values contained in this map.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

equals, hashCode

Constructor Detail

MemoryOptimizedMap

public MemoryOptimizedMap()

Method Detail

getOptimizedMap

public static <K,V> Map<K,V> getOptimizedMap(int size)

size

public int size()

Specified by:

size in interface Map<K,V>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map<K,V>

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map<K,V>

containsValue

public boolean containsValue(Object value)

Specified by:

containsValue in interface Map<K,V>

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>

putAll

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

Specified by:

putAll in interface Map<K,V>

clear

public void clear()

Specified by:

clear in interface Map<K,V>

optimize

public static <K,V> Map<K,V> optimize(Map<K,V> tab)

optimize

public static <K,V> Map<K,V> optimize(Map<K,V> tab,
                                      boolean growOnly)

deepOptimize

public static Map deepOptimize(Map tab)

optimizeInPlace

public static void optimizeInPlace(Map s)

keySet

public Set<K> keySet()

Returns a set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

keySet in interface Map<K,V>

Returns:

a set view of the keys contained in this map.

values

public Collection<V> values()

Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

values in interface Map<K,V>

Returns:

a collection view of the values contained in this map.

entrySet

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

Returns a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

entrySet in interface Map<K,V>

Returns:

a collection view of the mappings contained in this map.

See Also:

Map.Entry

clone

public Object clone()

Overrides:

clone in class Object