org.knopflerfish.util

Class CacheMap<K,V>

java.lang.Object

org.knopflerfish.util.CacheMap<K,V>

All Implemented Interfaces:

java.io.Serializable, java.util.Map<K,V>

public class CacheMap<K,V>
extends java.lang.Object
implements java.util.Map<K,V>, java.io.Serializable

Timeout version of a HashMap.

Entries in the map have a limited life-length, and the get method will only return the stored object during a limited time period.

After the timeout period, the object will be removed.

See Also:

CachedObject, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

java.util.Map.Entry<K,V>

Field Summary

Fields

Modifier and Type	Field and Description
protected long	timeout

Constructor Summary

Constructors

Constructor and Description
CacheMap() Create a map with default timeout period.
CacheMap(long timeout) Create a map with a specified timeout period.

Method Summary

Methods

Modifier and Type	Method and Description
void	clear()
boolean	containsKey(java.lang.Object key) Check if an object exists in the map.
boolean	containsValue(java.lang.Object value)
java.util.Set<java.util.Map.Entry<K,V>>	entrySet()
V	get(java.lang.Object key) Get an object from the map.
boolean	isEmpty()
java.util.Set<K>	keySet()
V	put(K key, V value) Store an object in the map.
void	putAll(java.util.Map<? extends K,? extends V> m)
V	remove(java.lang.Object key)
int	size()
void	update() Force timeout check on all items in map and remove all expired keys and objects.
java.util.Collection<V>	values()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

equals, hashCode

Field Detail

timeout

protected long timeout

Constructor Detail

CacheMap

public CacheMap()

Create a map with default timeout period.

Equivalent to CacheMap(CachedObject.DEFAULT_TIMEOUT)

See Also:

CachedObject.DEFAULT_TIMEOUT, CachedObject

CacheMap

public CacheMap(long timeout)

Create a map with a specified timeout period.

After an object has been stored in the map using put, it will only be available for timeout milliseconds. After that period, get will return null

Parameters:

timeout - timeout period in milliseconds for cached objects.

Method Detail

get

public V get(java.lang.Object key)

Get an object from the map. If the object's timeout period has expired, remove it from the map and return null.

Note: Since the timeout check is done for each cached object, be careful when looping over a map using iterators or other sequences of get. The result from a new get can become null faster than you might think. Thus always check for null return values from get.

Specified by:

get in interface java.util.Map<K,V>

containsKey

public boolean containsKey(java.lang.Object key)

Check if an object exists in the map. If non-existent or expired, return false.

Specified by:

containsKey in interface java.util.Map<K,V>

put

public V put(K key,
    V value)

Store an object in the map. The object's timeout period will start from the current system time.

Specified by:

put in interface java.util.Map<K,V>

update

public void update()

Force timeout check on all items in map and remove all expired keys and objects.

Normally, the timeout check is only done at get calls, but if necessary (for example at periodic complete printouts or before loops) you can (and probably want to) force a timeout check on all cached objects.

size

public int size()

Specified by:

size in interface java.util.Map<K,V>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface java.util.Map<K,V>

containsValue

public boolean containsValue(java.lang.Object value)

Specified by:

containsValue in interface java.util.Map<K,V>

remove

public V remove(java.lang.Object key)

Specified by:

remove in interface java.util.Map<K,V>

putAll

public void putAll(java.util.Map<? extends K,? extends V> m)

Specified by:

putAll in interface java.util.Map<K,V>

clear

public void clear()

Specified by:

clear in interface java.util.Map<K,V>

keySet

public java.util.Set<K> keySet()

Specified by:

keySet in interface java.util.Map<K,V>

values

public java.util.Collection<V> values()

Specified by:

values in interface java.util.Map<K,V>

entrySet

public java.util.Set<java.util.Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface java.util.Map<K,V>