org.limewire.collection
Class ForgetfulHashMap<K,V>

java.lang.Object
  java.util.AbstractMap<K,V>
      java.util.HashMap<K,V>
          org.limewire.collection.ForgetfulHashMap<K,V>

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>

public class ForgetfulHashMap<K,V>
extends HashMap<K,V>

A mapping that "forgets" keys and values using a FIFO replacement policy, much like a cache.

More formally, a ForgetfulHashMap is a sequence of key-value pairs [ (K1, V1), ... (KN, VN) ] ordered from youngest to oldest. When inserting a new pair, (KN, VN) is discarded if N is greater than a size (this threshold is fixed when the table is constructed). However, this property may not hold if keys are re-mapped to different values; if you need to re-map keys to different values, use FixedsizeForgetfulHashMap.

Technically, this is not a valid subtype of HashMap (since items can be removed), but HashMap makes implementation easy.

This class is not thread-safe.

    ForgetfulHashMap<String, String> fhm = new ForgetfulHashMap<String, String>(2);
    fhm.put("myKey1", "Abby");
    fhm.put("myKey2", "Bob");
    System.out.println(fhm);
    fhm.put("myKey3", "Chris");
    System.out.println(fhm);
    fhm.put("myKey3", "replace");
    System.out.println(fhm);

    Output:  
        {myKey2=Bob, myKey1=Abby}
        {myKey2=Bob, myKey3=Chris}
        {myKey3=replace}

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

ForgetfulHashMap(int size)
Create a new ForgetfulHashMap that holds only the last "size" entries.

Method Summary

V	put(K key, V value)
void	putAll(Map<? extends K,? extends V> t) Calls put on all keys in t.

Methods inherited from class java.util.HashMap

clear, clone, containsKey, containsValue, entrySet, get, isEmpty, keySet, 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

equals, hashCode

Constructor Detail

ForgetfulHashMap

public ForgetfulHashMap(int size)

Create a new ForgetfulHashMap that holds only the last "size" entries.

Parameters:

size - the number of entries to hold

Throws:

IllegalArgumentException - if size is less < 1.

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>

putAll

public void putAll(Map<? extends K,? extends V> t)

Calls put on all keys in t. See put(Object, Object) for specification.

Specified by:

putAll in interface Map<K,V>

Overrides:

putAll in class HashMap<K,V>