edu.tum.cs.commons.cache
Class SoftRefCacheBase<I,H,E,X extends Exception>

java.lang.Object
  edu.tum.cs.commons.cache.CacheBase<I,H,E,X>
      edu.tum.cs.commons.cache.SoftRefCacheBase<I,H,E,X>

Type Parameters:

I - the index type of the cache

H - the hash map key type

E - the type stored in the cache

X - the type of exception thrown by the CacheBase.obtainItem(Object) method. Use the NeverThrownRuntimeException if no exception will be thrown.

Direct Known Subclasses:

SoftRefStraightCacheBase

public abstract class SoftRefCacheBase<I,H,E,X extends Exception>
extends CacheBase<I,H,E,X>

A base class for dynamic caches based on SoftReferences. If identifiers itself are suitable hash keys, use class SoftRefStraightCacheBase.

The implementation is memory-sensitive, i.e. it dynamically removes entries from the cache if the virtual machine is short on memory. However, this dynamic is completely transparent to the user.

Note: To make this cache efficient the virtual machine must work in server mode.

Version:

$Rev: 26268 $

Author:

Florian Deissenboeck, Tilman Seifert, $Author: juergens $

Rating:

GREEN Hash: A74130243CAE0E00D2C6A51DDFEA68A0

Field Summary

protected HashMap<H,SoftReference<E>>

cache The actual cache.

Constructor Summary

SoftRefCacheBase()

Method Summary

E	getItem(I identifier) Obtain an item from the cache.
static String	getStatistics() Returns a statistics string with information about cache hits and misses for debugging purposes.

Methods inherited from class edu.tum.cs.commons.cache.CacheBase

getHashKey, obtainItem

Methods inherited from class java.lang.Object

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

Field Detail

cache

protected final HashMap<H,SoftReference<E>> cache

The actual cache.

Constructor Detail

SoftRefCacheBase

public SoftRefCacheBase()

Method Detail

getItem

public E getItem(I identifier)
          throws X extends Exception

Obtain an item from the cache. If the item was not cached yet, it will be cached.

Specified by:

getItem in class CacheBase<I,H,E,X extends Exception>

Parameters:

identifier - an object identifying the item to retrieve from the cache. This class' implementation works with a hash map so identifiers must adhere to the conventions for Object.hashcode().

Returns:

The item.

Throws:

X extends Exception

getStatistics

public static String getStatistics()

Returns a statistics string with information about cache hits and misses for debugging purposes. As this is implemented in a static way results are only valid if only a single instance of the specific cache class exists.