com.mckoi.util
Class Cache

java.lang.Object
  extended by com.mckoi.util.Cache

public class Cache
extends java.lang.Object

Represents a cache of Objects. A Cache is similar to a Hashtable, in that you can 'add' and 'get' objects from the container given some key. However a cache may remove objects from the container when it becomes too full.

The cache scheme uses a doubly linked-list hashtable. The most recently accessed objects are moved to the start of the list. The end elements in the list are wiped if the cache becomes too full.

Author:
Tobias Downer

Constructor Summary
Cache()
           
Cache(int max_size)
           
Cache(int max_size, int clean_percentage)
           
Cache(int hash_size, int max_size, int clean_percentage)
          The Constructors.
 
Method Summary
protected  void checkClean()
          This is called whenever at Object is put into the cache.
protected  int clean()
          Cleans away some old elements in the cache.
 void clear()
           
 java.lang.Object get(java.lang.Object key)
          If the cache contains the cell with the given key, this method will return the object.
protected  int getHashSize()
          Deprecated.  
 int nodeCount()
          Returns the number of nodes that are currently being stored in the cache.
protected  void notifyGetWalks(long total_walks, long total_get_ops)
          Notifies that some statistical information about the hash map has updated.
protected  void notifyWipingNode(java.lang.Object ob)
          Notifies that the given object has been wiped from the cache by the clean up procedure.
 void put(java.lang.Object key, java.lang.Object ob)
          Puts an Object into the cache with the given key.
 java.lang.Object remove(java.lang.Object key)
          Ensures that there is no cell with the given key in the cache.
 void removeAll()
          Clear the cache of all the entries.
protected  boolean shouldWipeMoreNodes()
          Returns true if the clean-up method that periodically cleans up the cache, should clean up more elements from the cache.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Cache

public Cache(int hash_size,
             int max_size,
             int clean_percentage)
The Constructors. It takes a maximum size the cache can grow to, and the percentage of the cache that is wiped when it becomes too full.


Cache

public Cache(int max_size,
             int clean_percentage)

Cache

public Cache(int max_size)

Cache

public Cache()
Method Detail

getHashSize

protected final int getHashSize()
Deprecated. 

Creates the HashMap object to store objects in this cache. This is available to be overwritten.


checkClean

protected void checkClean()
This is called whenever at Object is put into the cache. This method should determine if the cache should be cleaned and call the clean method if appropriate.


shouldWipeMoreNodes

protected boolean shouldWipeMoreNodes()
Returns true if the clean-up method that periodically cleans up the cache, should clean up more elements from the cache.


notifyWipingNode

protected void notifyWipingNode(java.lang.Object ob)
Notifies that the given object has been wiped from the cache by the clean up procedure.


notifyGetWalks

protected void notifyGetWalks(long total_walks,
                              long total_get_ops)
Notifies that some statistical information about the hash map has updated. This should be used to compile statistical information about the number of walks a 'get' operation takes to retreive an entry from the hash.

This method is called every 8192 gets.


nodeCount

public final int nodeCount()
Returns the number of nodes that are currently being stored in the cache.


put

public final void put(java.lang.Object key,
                      java.lang.Object ob)
Puts an Object into the cache with the given key.


get

public final java.lang.Object get(java.lang.Object key)
If the cache contains the cell with the given key, this method will return the object. If the cell is not in the cache, it returns null.


remove

public final java.lang.Object remove(java.lang.Object key)
Ensures that there is no cell with the given key in the cache. This is useful for ensuring the cache does not contain out-dated information.


removeAll

public void removeAll()
Clear the cache of all the entries.


clear

public void clear()

clean

protected final int clean()
Cleans away some old elements in the cache. This method walks from the end, back 'wipe_count' elements putting each object on the recycle stack.