Package org.apache.mina.util

Class LazyInitializedCacheMap<K,V>

java.lang.Object

org.apache.mina.util.LazyInitializedCacheMap<K,V>

Type Parameters:

K - The key type

V - The value type

All Implemented Interfaces:

Map<K,V>

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

This map is specially useful when reads are much more frequent than writes and if the cost of instantiating the values is high like allocating an IoBuffer for example. Based on the final implementation of Memoizer written by Brian Goetz and Tim Peierls. This implementation will return an UnsupportedOperationException on each method that is not intended to be called by user code for performance reasons.

Since:

MINA 2.0.0-M2

Author:

Apache MINA Project

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
class	LazyInitializedCacheMap.NoopInitializer	This class provides a noop LazyInitializer meaning it will return the same object it received when instantiated.

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

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

Constructor Summary

Constructors

Constructor	Description
LazyInitializedCacheMap()	Default constructor.
LazyInitializedCacheMap(ConcurrentHashMap<K,LazyInitializer<V>> map)	This constructor allows to provide a fine tuned ConcurrentHashMap to stick with each special case the user needs.

Method Summary

Modifier and Type	Method	Description
void	clear()
boolean	containsKey(Object key)
boolean	containsValue(Object value)	Throws UnsupportedOperationException as this method would imply performance drops.
Set<Map.Entry<K,V>>	entrySet()	Throws UnsupportedOperationException as this method would imply performance drops.
V	get(Object key)
Collection<LazyInitializer<V>>	getValues()
boolean	isEmpty()
Set<K>	keySet()
V	put(K key, V value)
void	putAll(Map<? extends K,? extends V> m)
V	putIfAbsent(K key, LazyInitializer<V> value)	If the specified key is not already associated with a value, associate it with the given value.
V	remove(Object key)
int	size()
Collection<V>	values()	Throws UnsupportedOperationException as this method would imply performance drops.

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

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

Constructor Detail

LazyInitializedCacheMap

public LazyInitializedCacheMap()

Default constructor. Uses the default parameters to initialize its internal ConcurrentHashMap.

LazyInitializedCacheMap

public LazyInitializedCacheMap(ConcurrentHashMap<K,LazyInitializer<V>> map)

This constructor allows to provide a fine tuned ConcurrentHashMap to stick with each special case the user needs.

Parameters:

map - The map to use as a cache

Method Detail

get

public V get(Object key)

Specified by:

get in interface Map<K,V>

remove

public V remove(Object key)

Specified by:

remove in interface Map<K,V>

putIfAbsent

public V putIfAbsent(K key,
                     LazyInitializer<V> value)

If the specified key is not already associated with a value, associate it with the given value. This is equivalent to

   if (!map.containsKey(key))
       return map.put(key, value);
   else
       return map.get(key);

except that the action is performed atomically.

Parameters:

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

value - a lazy initialized value object.

Returns:

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

put

public V put(K key,
             V value)

Specified by:

put in interface Map<K,V>

containsValue

public boolean containsValue(Object value)

Throws UnsupportedOperationException as this method would imply performance drops.

Specified by:

containsValue in interface Map<K,V>

values

public Collection<V> values()

Throws UnsupportedOperationException as this method would imply performance drops.

Specified by:

values in interface Map<K,V>

entrySet

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

Throws UnsupportedOperationException as this method would imply performance drops.

Specified by:

entrySet in interface Map<K,V>

putAll

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

Specified by:

putAll in interface Map<K,V>

getValues

public Collection<LazyInitializer<V>> getValues()

Returns:

return the values from the cache

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>

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>

size

public int size()

Specified by:

size in interface Map<K,V>