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pspdash
Class MRUCache  view MRUCache download MRUCache.java

java.lang.Object
  extended bypspdash.MRUCache
All Implemented Interfaces:
java.util.Map

public class MRUCache
extends java.lang.Object
implements java.util.Map

Simple implementation of a most-recently-used cache. Works like a hashtable, but only retains a fixed number of mappings. When too many key-value pairs are added, the least recently used pairs are flushed to remain under the user-set maximum capacity.


Nested Class Summary
 
Nested classes inherited from class java.util.Map
java.util.Map.Entry
 
Field Summary
private  java.util.Map cache
           
private  int maxCacheItems
           
private  java.util.LinkedList mruList
           
 
Constructor Summary
MRUCache()
           
MRUCache(int maxCapacity)
           
 
Method Summary
 void clear()
          Remove all entries from this Map (optional operation).
 boolean containsKey(java.lang.Object k)
          Returns true if this contains a mapping for the given key.
 boolean containsValue(java.lang.Object v)
          Returns true if this contains at least one mapping with the given value.
 java.util.Set entrySet()
          Returns a set view of the mappings in this Map.
 boolean equals(java.lang.Object obj)
          Compares the specified object with this map for equality.
 java.lang.Object get(java.lang.Object key)
          Returns the value mapped by the given key.
 int hashCode()
          Returns the hash code for this map.
 boolean isEmpty()
          Returns true if the map contains no mappings.
 java.util.Set keySet()
          Returns a set view of the keys in this Map.
 java.lang.Object put(java.lang.Object key, java.lang.Object value)
          Associates the given key to the given value (optional operation).
 void putAll(java.util.Map m)
          Copies all entries of the given map to this one (optional operation).
 java.lang.Object remove(java.lang.Object key)
          Removes the mapping for this key if present (optional operation).
 int size()
          Returns the number of key-value mappings in the map.
private  void touchItem(java.lang.Object key)
           
 java.util.Collection values()
          Returns a collection (or bag) view of the values in this Map.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

cache

private java.util.Map cache

mruList

private java.util.LinkedList mruList

maxCacheItems

private int maxCacheItems
Constructor Detail

MRUCache

public MRUCache()

MRUCache

public MRUCache(int maxCapacity)
Method Detail

touchItem

private void touchItem(java.lang.Object key)

hashCode

public int hashCode()
Description copied from interface: java.util.Map
Returns the hash code for this map. This is the sum of all hashcodes for each Map.Entry object in entrySet. This allows comparison of maps, regardless of implementation, and satisfies the contract of Object.hashCode.

Specified by:
hashCode in interface java.util.Map

equals

public boolean equals(java.lang.Object obj)
Description copied from interface: java.util.Map
Compares the specified object with this map for equality. Returns true if the other object is a Map with the same mappings, that is,
o instanceof Map && entrySet().equals(((Map) o).entrySet(); This allows comparison of maps, regardless of implementation.

Specified by:
equals in interface java.util.Map

size

public int size()
Description copied from interface: java.util.Map
Returns the number of key-value mappings in the map. If there are more than Integer.MAX_VALUE mappings, return Integer.MAX_VALUE.

Specified by:
size in interface java.util.Map

values

public java.util.Collection values()
Description copied from interface: java.util.Map
Returns a collection (or bag) view of the values in this Map. The collection is backed by the map, so that changes in one show up in the other. Modifications made while an iterator is in progress cause undefined behavior. If the collection supports removal, these methods remove the underlying mapping from the map: Iterator.remove, Collection.remove, removeAll, retainAll, and clear. Element addition, via add or addAll, is not supported via this collection.

Specified by:
values in interface java.util.Map

keySet

public java.util.Set keySet()
Description copied from interface: java.util.Map
Returns a set view of the keys in this Map. The set is backed by the map, so that changes in one show up in the other. Modifications made while an iterator is in progress cause undefined behavior. If the set supports removal, these methods remove the underlying mapping from the map: Iterator.remove, Set.remove, removeAll, retainAll, and clear. Element addition, via add or addAll, is not supported via this set.

Specified by:
keySet in interface java.util.Map

entrySet

public java.util.Set entrySet()
Description copied from interface: java.util.Map
Returns a set view of the mappings in this Map. Each element in the set is a Map.Entry. The set is backed by the map, so that changes in one show up in the other. Modifications made while an iterator is in progress cause undefined behavior. If the set supports removal, these methods remove the underlying mapping from the map: Iterator.remove, Set.remove, removeAll, retainAll, and clear. Element addition, via add or addAll, is not supported via this set.

Specified by:
entrySet in interface java.util.Map

isEmpty

public boolean isEmpty()
Description copied from interface: java.util.Map
Returns true if the map contains no mappings.

Specified by:
isEmpty in interface java.util.Map

containsValue

public boolean containsValue(java.lang.Object v)
Description copied from interface: java.util.Map
Returns true if this contains at least one mapping with the given value. In other words, returns true if a value v exists where (value == null ? v == null : value.equals(v)). This usually requires linear time.

Specified by:
containsValue in interface java.util.Map

containsKey

public boolean containsKey(java.lang.Object k)
Description copied from interface: java.util.Map
Returns true if this contains a mapping for the given key.

Specified by:
containsKey in interface java.util.Map

put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object value)
Description copied from interface: java.util.Map
Associates the given key to the given value (optional operation). If the map already contains the key, its value is replaced. Be aware that in a map that permits null values, a null return does not always imply that the mapping was created.

Specified by:
put in interface java.util.Map

get

public java.lang.Object get(java.lang.Object key)
Description copied from interface: java.util.Map
Returns the value mapped by the given key. Returns null if there is no mapping. However, in Maps that accept null values, you must rely on containsKey to determine if a mapping exists.

Specified by:
get in interface java.util.Map

remove

public java.lang.Object remove(java.lang.Object key)
Description copied from interface: java.util.Map
Removes the mapping for this key if present (optional operation). If the key is not present, this returns null. Note that maps which permit null values may also return null if the key was removed.

Specified by:
remove in interface java.util.Map

clear

public void clear()
Description copied from interface: java.util.Map
Remove all entries from this Map (optional operation).

Specified by:
clear in interface java.util.Map

putAll

public void putAll(java.util.Map m)
Description copied from interface: java.util.Map
Copies all entries of the given map to this one (optional operation). If the map already contains a key, its value is replaced.

Specified by:
putAll in interface java.util.Map