de.jakop.lotus.domingo.cache

Class WeakCache

java.lang.Object

de.jakop.lotus.domingo.cache.AbstractBaseCache

de.jakop.lotus.domingo.cache.WeakCache

All Implemented Interfaces:

Cache, Serializable

public final class WeakCache
extends AbstractBaseCache
implements Serializable

Weak Cache.

This implementation of the Cache interface uses a WeakHashMap to store the keys. The values are stored as WeakReferences.

Note that this implementation is synchronized. Multiple threads can access this map concurrently.

Author:

Kurt Riede

See Also:

WeakHashMap, WeakReference, Serialized Form

Constructor Summary

Constructors

Constructor and Description
WeakCache() Creates a new WeakCache object.

Method Summary

Modifier and Type	Method and Description
void	clear() Removes all mappings from this map (optional operation).
boolean	containsKey(Object key) Checks if a given key exists in the cache.
protected Map	createMap() Creates the map to be used with the cache.
Object	get(Object key) Returns an object with a given key from the cache.
Set	keySet() Returns a set view of the keys contained in this cache.
void	put(Object key, Object value) Puts an object with a key into the cache.
Object	remove(Object key) Removes the mapping for this key from this cache if present (optional operation).
Collection	values() Returns a collection view of the values contained in this cache.

Methods inherited from class de.jakop.lotus.domingo.cache.AbstractBaseCache

getMap, size

Methods inherited from class java.lang.Object

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

Constructor Detail

WeakCache

public WeakCache()

Creates a new WeakCache object.

Method Detail

createMap

protected Map createMap()

Creates the map to be used with the cache.

Concrete classes must implement this method and create a concrete map for the cache.

Specified by:

createMap in class AbstractBaseCache

Returns:

a map for the cache

See Also:

AbstractBaseCache.createMap()

put

public void put(Object key,
                Object value)

Puts an object with a key into the cache.

Specified by:

put in interface Cache

Parameters:

key - the key

value - the object

See Also:

Cache.put(java.lang.Object, java.lang.Object), WeakReference, Cache.put(java.lang.Object, java.lang.Object)

get

public Object get(Object key)

Returns an object with a given key from the cache.

Specified by:

get in interface Cache

Parameters:

key - the key

Returns:

object with given key

See Also:

Cache.get(java.lang.Object)

containsKey

public boolean containsKey(Object key)

Checks if a given key exists in the cache.

Specified by:

containsKey in interface Cache

Parameters:

key - the key

Returns:

true if the given key exists in the cache, else false

See Also:

Cache.containsKey(java.lang.Object)

remove

public Object remove(Object key)

Removes the mapping for this key from this cache if present (optional operation).

This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, its value is obtained with its getValue operation, the entry is removed from the Collection (and the backing cache) with the iterator's remove operation, and the saved value is returned. If the iteration terminates without finding such an entry, null is returned. Note that this implementation requires linear time in the size of the cache; many implementations will override this method.

Specified by:

remove in interface Cache

Parameters:

key - key whose mapping is to be removed from the cache.

Returns:

previous value associated with specified key, or null if there was no entry for key. (A null return can also indicate that the cache previously associated null with the specified key, if the implementation supports null values.)

See Also:

Cache.remove(java.lang.Object)

clear

public void clear()

Removes all mappings from this map (optional operation).

Specified by:

clear in interface Cache

See Also:

Cache.clear()

keySet

public Set keySet()

Returns a set view of the keys contained in this cache. The set is backed by the cache, so changes to the cache are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from this cache, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

keySet in interface Cache

Returns:

a set view of the keys contained in this cache.

See Also:

Cache.keySet()

values

public Collection values()

Returns a collection view of the values contained in this cache. The collection is backed by the cache, so changes to the cache are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from this cache, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

values in interface Cache

Returns:

a collection view of the values contained in this cache.

See Also:

Cache.values()