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Class sun.server.util.LRUCache 

java.lang.Object
   |
   +----java.util.Dictionary
           |
           +----java.util.Hashtable
                   |
                   +----sun.server.util.LRUCache
public class LRUCache
extends Hashtable
The LRUCache is a bounded hashtable where the least recently used entries are purged from the hashtable to make room for new ones. The objects stored are all mandated to implement the cacheable interface. This LRUCache is bounded by a configurable size. Whenever a new Cacheable object is inserted, its made sure that the size of the cache remains below the configured maximum. If the maximum would be exceeded by adding this new element, old least recently used elements are thrown out until the enough room is made for the new element. If enough room cannot be made for the new element, an OutOfMemory exception is thrown.

See Also:
Cacheable

Constructor Index

o LRUCache(int)
Constructs a new, empty LRUCache.
o LRUCache(int, float, int)
Constructs a new, empty LRUCache with the specified initial capacity, the specified load factor and the specified max number of entries.
o LRUCache(int, int)
Constructs a new, empty LRUCache with the specified initial capacity.

Method Index

o get(Object)
Gets the object associated with the specified key in the hashtable.
o getAvailableSize()
The total amount of free space available in the cache for storing new elements
o getTotalSize()
The total size this cache was configured with at construction time.
o put(Object, Cacheable)
Puts the specified element into the hashtable, using the specified key.
o put(Object, Object)
Only Cacheable entries can be stored in this cache.
o remove(Object)
Removes the element corresponding to the key.

Constructors

o LRUCache 
 public LRUCache(int initialCapacity,
                 float loadFactor,
                 int maxSize)
Constructs a new, empty LRUCache with the specified initial capacity, the specified load factor and the specified max number of entries.

Parameters:
initialCapacity - the initial number of buckets
loadFactor - a number between 0.0 and 1.0, it defines the threshold for rehashing the LRUCache into a bigger one.
maxSize - - the maximum size this cache can grow to. Once this size limit is reached, entries will be thrown away in LRU to make space for new entries in the cache.
Throws: IllegalArgumentException
If the initial capacity is less than or equal to zero.
Throws: IllegalArgumentException
If the load factor is less than or equal to zero.
o LRUCache 
 public LRUCache(int initialCapacity,
                 int maxSize)
Constructs a new, empty LRUCache with the specified initial capacity.

Parameters:
initialCapacity - the initial number of buckets
maxSize - - the maximum size this cache can grow to. Once this size limit is reached, entries will be thrown away in LRU to make space for new entries in the cache.
o LRUCache 
 public LRUCache(int maxSize)
Constructs a new, empty LRUCache. A default capacity and load factor is used. Note that the LRUCache will automatically grow when it gets full.

Parameters:
maxSize - - the maximum size this cache can grow to. Once this size limit is reached, entries will be thrown away in LRU to make space for new entries in the cache.

Methods

o put 
 public synchronized Object put(Object key,
                                Cacheable c)
Puts the specified element into the hashtable, using the specified key. The element may be retrieved by doing a get() with the same key. The key and the element cannot be null.

Parameters:
key - the specified key in the hashtable
value - the specified element that implements the Cacheable interface
Returns:
the old value of the key, or null if it did not have one.
Throws: NullPointerException
If the value of the element is equal to null.
Throws: OutOfMemoryError
If the cache cannot accomodate the size of the object.
See Also:
get
o put 
 public synchronized Object put(Object key,
                                Object value)
Only Cacheable entries can be stored in this cache. An attempt to insert anything else results in an IllegalArgumentException

Parameters:
key - the specified key in the hashtable
value - the specified element that implements the Cacheable interface
Returns:
the old value of the key, or null if it did not have one.
Throws: IllegalArgumentException
if Object does not implement Cacheable
Overrides:
put in class Hashtable
See Also:
get
o get 
 public synchronized Object get(Object key)
Gets the object associated with the specified key in the hashtable.

Parameters:
key - the specified key
Returns:
s the element for the key or null if the key is not defined in the hash table.
Overrides:
get in class Hashtable
See Also:
put
o remove 
 public synchronized Object remove(Object key)
Removes the element corresponding to the key. Does nothing if the key is not present.

Parameters:
key - the key that needs to be removed
Returns:
the value of key, or null if the key was not found.
Overrides:
remove in class Hashtable
o getAvailableSize 
 public int getAvailableSize()
The total amount of free space available in the cache for storing new elements

o getTotalSize 
 public int getTotalSize()
The total size this cache was configured with at construction time. 

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