net.tomp2p.utils

Class CacheMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<K,V>

java.util.LinkedHashMap<K,V>

net.tomp2p.utils.CacheMap<K,V>

Type Parameters:

K - The key

V - The value

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>

public class CacheMap<K,V>
extends LinkedHashMap<K,V>

The CacheMap is a LRU cache with a given capacity. The elements that do not fit into the cache will be removed. The flag updateEntryOnInsert will determine if put(Object, Object) or putIfAbsent(Object, Object) will be used. This is useful for entries that have timing information and that should not be updated if the same key is going to be used. This class extends LinkedHashMap, which means that this class is not thread safe.

Author:

Thomas Bocek

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Constructor Summary

Constructors

Constructor and Description
CacheMap(int maxEntries, boolean updateEntryOnInsert) Creates a new CacheMap with a fixed capacity.

Method Summary

Methods

Modifier and Type	Method and Description
V	put(K key, V value)
V	putIfAbsent(K key, V value) If the key is not associated with a value, associate it with the value.
protected boolean	removeEldestEntry(Map.Entry<K,V> eldest)

Methods inherited from class java.util.LinkedHashMap

clear, containsValue, get

Methods inherited from class java.util.HashMap

clone, containsKey, entrySet, isEmpty, keySet, putAll, remove, size, values

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

containsKey, entrySet, equals, hashCode, isEmpty, keySet, putAll, remove, size, values

Constructor Detail

CacheMap

public CacheMap(int maxEntries,
        boolean updateEntryOnInsert)

Creates a new CacheMap with a fixed capacity.

Parameters:

maxEntries - The number of entries that can be stored in this map

updateEntryOnInsert - Set to true to update (overwrite) values. Set false to not overwrite the values if there is a value present.

Method Detail

put

public V put(K key,
    V value)

Specified by:

put in interface Map<K,V>

Overrides:

put in class HashMap<K,V>

putIfAbsent

public V putIfAbsent(K key,
            V value)

If the key is not associated with a value, associate it with the value. This is the same as:

 if (!map.containsKey(key)) {
     return map.put(key, value);
 } else {
     return map.get(key);
 }
 

Parameters:

key - key with which the value is to be associated.

value - value to be associated with the key.

Returns:

previous value associated with key, or null if there was no mapping for this key.

removeEldestEntry

protected boolean removeEldestEntry(Map.Entry<K,V> eldest)

Overrides:

removeEldestEntry in class LinkedHashMap<K,V>