org.simpleframework.xml.util
Class LimitedCache<T>

java.lang.Object
  extended by java.util.AbstractMap<K,V>
      extended by java.util.HashMap<K,V>
          extended by java.util.LinkedHashMap<Object,T>
              extended by org.simpleframework.xml.util.LimitedCache<T>
All Implemented Interfaces:
Serializable, Cloneable, Map<Object,T>, Cache<T>

public class LimitedCache<T>
extends LinkedHashMap<Object,T>
implements Cache<T>

The LimitedCache interface is used to represent a cache that will store key value pairs. This implementation is backed by a LinkedHashMap so that only a specific number of elements can be stored in the cache at one time.

Author:
Niall Gallagher
See Also:
Serialized Form

Nested Class Summary
 
Nested classes/interfaces inherited from class java.util.AbstractMap
AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>
 
Constructor Summary
LimitedCache()
          Constructor of the LimitedCache object.
LimitedCache(int capacity)
          Constructor of the LimitedCache object.
 
Method Summary
 void cache(Object key, T value)
          This method is used to insert a key value mapping in to the cache.
 boolean contains(Object key)
          This is used to determine whether the specified key exists with in the cache.
 T fetch(Object key)
          This method is used to get the value from the cache that is mapped to the specified key.
protected  boolean removeEldestEntry(Map.Entry<Object,T> entry)
          This is used to remove the eldest entry from the cache.
 T take(Object key)
          This is used to exclusively take the value mapped to the specified key from the cache.
 
Methods inherited from class java.util.LinkedHashMap
clear, containsValue, get
 
Methods inherited from class java.util.HashMap
clone, containsKey, entrySet, isEmpty, keySet, put, putAll, remove, size, values
 
Methods inherited from class java.util.AbstractMap
equals, hashCode, toString
 
Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface org.simpleframework.xml.util.Cache
isEmpty
 
Methods inherited from interface java.util.Map
containsKey, entrySet, equals, hashCode, isEmpty, keySet, put, putAll, remove, size, values
 

Constructor Detail

LimitedCache

public LimitedCache()
Constructor of the LimitedCache object. This is used to create a cache with a fixed size. The strategy for this cache is least recently used. Any insert or fetch from the cache is considered to be a use.


LimitedCache

public LimitedCache(int capacity)
Constructor of the LimitedCache object. This is used to create a cache with a fixed size. The strategy for this cache is least recently used. Any insert or fetch from the cache is considered to be a use.

Parameters:
capacity - this is the capacity of the cache object
Method Detail

cache

public void cache(Object key,
                  T value)
This method is used to insert a key value mapping in to the cache. The value can later be retrieved or removed from the cache if desired. If the value associated with the key is null then nothing is stored within the cache.

Specified by:
cache in interface Cache<T>
Parameters:
key - this is the key to cache the provided value to
value - this is the value that is to be cached

take

public T take(Object key)
This is used to exclusively take the value mapped to the specified key from the cache. Invoking this is effectively removing the value from the cache.

Specified by:
take in interface Cache<T>
Parameters:
key - this is the key to acquire the cache value with
Returns:
this returns the value mapped to the specified key

fetch

public T fetch(Object key)
This method is used to get the value from the cache that is mapped to the specified key. If there is no value mapped to the specified key then this method will return a null.

Specified by:
fetch in interface Cache<T>
Parameters:
key - this is the key to acquire the cache value with
Returns:
this returns the value mapped to the specified key

contains

public boolean contains(Object key)
This is used to determine whether the specified key exists with in the cache. Typically this can be done using the fetch method, which will acquire the object.

Specified by:
contains in interface Cache<T>
Parameters:
key - this is the key to check within this segment
Returns:
true if the specified key is within the cache

removeEldestEntry

protected boolean removeEldestEntry(Map.Entry<Object,T> entry)
This is used to remove the eldest entry from the cache. The eldest entry is removed from the cache if the size of the map grows larger than the maximum entries permitted.

Overrides:
removeEldestEntry in class LinkedHashMap<Object,T>
Parameters:
entry - this is the eldest entry that can be removed
Returns:
this returns true if the entry should be removed