org.exolab.castor.persist
Class LRU

java.lang.Object
  org.exolab.castor.persist.LRU

Direct Known Subclasses:

LRU.CountLimited, LRU.NoCache, LRU.TimeLimited, LRU.Unlimited

public abstract class LRU

extends java.lang.Object

Base interface for all least-recently-used cache.

Author:

Thomas Yip

Nested Class Summary

static class	LRU.CountLimited CountLimited is a count limted least-recently-used Map.
static class	LRU.NoCache NoCache is a Map which dispose all object right the way.
static class	LRU.TimeLimited TimeLimited is a time limted least-recently-used Map.
static class	LRU.Unlimited UnLimited is Map which implements the LRU interface.

Field Summary

static int	CACHE_COUNT_LIMITED Map type of Count-Limited least-recently-used as caching mechanism.
static int	CACHE_NONE Map type for no caching as the caching mechanism.
static int	CACHE_TIME_LIMITED Map type of Time-Limited least-recently-used is used as caching mechanism.
static int	CACHE_UNLIMITED Map type of unlimited cache as caching mechanism.
static int	DEFAULT_PARAM Specify the default LRU parameter
static int	DEFAULT_TYPE Specify the default LRU mechanism

Constructor Summary

LRU()

Method Summary

static LRU	create(int type, int param) Factory method to create a LRU map of specified type.
abstract java.util.Enumeration	elements() Returns an enumeration of the values in this LRU map.
abstract java.lang.Object	get(java.lang.Object key) Returns the value to which the specified key is mapped in this hashtable.
static int	mapType(java.lang.String type) Map the type in String into an int to represent the lru cache type.
abstract java.lang.Object	put(java.lang.Object key, java.lang.Object value) Maps the specified key to the specified value in this hashtable.
abstract java.lang.Object	remove(java.lang.Object key) Removes the key (and its corresponding value) from this hashtable.

Methods inherited from class java.lang.Object

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

Field Detail

CACHE_NONE

public static final int CACHE_NONE

Map type for no caching as the caching mechanism. All object put into the map will be discarded.

See Also:

Constant Field Values

CACHE_COUNT_LIMITED

public static final int CACHE_COUNT_LIMITED

Map type of Count-Limited least-recently-used as caching mechanism. Object Lock which is not hold by any transcation will be put in the cache, until the cache is full and other object overwritten it.

See Also:

Constant Field Values

CACHE_TIME_LIMITED

public static final int CACHE_TIME_LIMITED

Map type of Time-Limited least-recently-used is used as caching mechanism. Object Lock which is not hold by any transcation will be put in the cache, until timeout is reached.

See Also:

Constant Field Values

CACHE_UNLIMITED

public static final int CACHE_UNLIMITED

Map type of unlimited cache as caching mechanism. Object Lock which is not hold by any transcation will be put in the cache for later use.

See Also:

Constant Field Values

DEFAULT_TYPE

public static final int DEFAULT_TYPE

Specify the default LRU mechanism

See Also:

Constant Field Values

DEFAULT_PARAM

public static final int DEFAULT_PARAM

Specify the default LRU parameter

See Also:

Constant Field Values

Constructor Detail

LRU

public LRU()

Method Detail

put

public abstract java.lang.Object put(java.lang.Object key,
                                     java.lang.Object value)

Maps the specified key to the specified value in this hashtable. Neither the key nor the value can be null.

The value can be retrieved by calling the get method with a key that is equal to the original key, before it is diposed by the least-recently-used map.

Parameters:

key - the hashtable key.

value - the value.

Returns:

the previous value of the specified key in this hashtable, or null if it did not have one.

Throws:

java.lang.NullPointerException - if the key or value is null.

get

public abstract java.lang.Object get(java.lang.Object key)

Returns the value to which the specified key is mapped in this hashtable.

Parameters:

key - - a key in the hashtable.

Returns:

the value to which the key is mapped in this hashtable; null if the key is not mapped to any value in this hashtable.

remove

public abstract java.lang.Object remove(java.lang.Object key)

Removes the key (and its corresponding value) from this hashtable. This method does nothing if the key is not in the hashtable.

Parameters:

key - the key that needs to be removed.

Returns:

the value to which the key had been mapped in this hashtable, or null if the key did not have a mapping.

elements

public abstract java.util.Enumeration elements()

Returns an enumeration of the values in this LRU map. Use the Enumeration methods on the returned object to fetch the elements sequentially.

Returns:

an enumeration of the values in this hashtable.

See Also:

Enumeration

create

public static LRU create(int type,
                         int param)

Factory method to create a LRU map of specified type.

Parameters:

type - mechanism type

param - capacity of the lru

mapType

public static int mapType(java.lang.String type)

Map the type in String into an int to represent the lru cache type.