DefaultCache (Core XMPP Server 4.3.1 API)

java.lang.Object
- org.jivesoftware.util.cache.DefaultCache<K,V>

All Implemented Interfaces:

Map<K,V>, Cache<K,V>
```
public class DefaultCache<K extends Serializable,V extends Serializable>
extends Object
implements Cache<K,V>
```
Default, non-distributed implementation of the Cache interface. The algorithm for cache is as follows: a HashMap is maintained for fast object lookup. Two linked lists are maintained: one keeps objects in the order they are accessed from cache, the other keeps objects in the order they were originally added to cache. When objects are added to cache, they are first wrapped by a CacheObject which maintains the following pieces of information:
- The size of the object (in bytes).
- A pointer to the node in the linked list that maintains accessed order for the object. Keeping a reference to the node lets us avoid linear scans of the linked list.
- A pointer to the node in the linked list that maintains the age of the object in cache. Keeping a reference to the node lets us avoid linear scans of the linked list.
To get an object from cache, a hash lookup is performed to get a reference to the CacheObject that wraps the real object we are looking for. The object is subsequently moved to the front of the accessed linked list and any necessary cache cleanups are performed. Cache deletion and expiration is performed as needed.
Author:

Matt Tucker

Nested Class Summary
- Nested classes/interfaces inherited from interface java.util.Map
  Map.Entry<K,V>

Field Summary

Fields
Modifier and Type	Field and Description
`protected LinkedList<K>`	`ageList` Linked list to maintain time that cache objects were initially added to the cache, most recently added to oldest added.
`protected long`	`cacheHits` Maintain the number of cache hits and misses.
`protected long`	`cacheMisses` Maintain the number of cache hits and misses.
`protected LinkedList<K>`	`lastAccessedList` Linked list to maintain order that cache objects are accessed in, most used to least used.
`protected Map<K,org.jivesoftware.util.cache.DefaultCache.CacheObject<V>>`	`map` The map the keys and values are stored in.
`protected long`	`maxLifetime` Maximum length of time objects can exist in cache before expiring.

Constructor Summary

Constructors
Constructor and Description
`DefaultCache(String name, long maxSize, long maxLifetime)` Create a new default cache and specify the maximum size of for the cache in bytes, and the maximum lifetime of objects.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`clear()`
`boolean`	`containsKey(Object key)`
`boolean`	`containsValue(Object value)`
`protected void`	`cullCache()` Removes objects from cache if the cache is too full.
`protected void`	`deleteExpiredEntries()` Clears all entries out of cache where the entries are older than the maximum defined age.
`Set<Map.Entry<K,V>>`	`entrySet()`
`V`	`get(Object key)`
`long`	`getCacheCulls(Duration duration)`
`long`	`getCacheHits()` Returns the number of cache hits.
`long`	`getCacheMisses()` Returns the number of cache misses.
`int`	`getCacheSize()` Returns the size of the cache contents in bytes.
`long`	`getMaxCacheSize()` Returns the maximum size of the cache (in bytes).
`long`	`getMaxLifetime()` Returns the maximum number of milleseconds that any object can live in cache.
`String`	`getName()` Returns the name of this cache.
`boolean`	`isEmpty()`
`Set<K>`	`keySet()`
`V`	`put(K key, V value)`
`void`	`putAll(Map<? extends K,? extends V> map)`
`V`	`remove(Object key)`
`void`	`setMaxCacheSize(int maxCacheSize)` Sets the maximum size of the cache.
`void`	`setMaxLifetime(long maxLifetime)` Sets the maximum number of milleseconds that any object can live in cache.
`void`	`setName(String name)` Sets the name of this cache.
`int`	`size()`
`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
compute, computeIfAbsent, computeIfPresent, equals, forEach, getOrDefault, hashCode, merge, putIfAbsent, remove, replace, replace, replaceAll

- Field Detail
  - map
```
protected Map<K extends Serializable,org.jivesoftware.util.cache.DefaultCache.CacheObject<V extends Serializable>> map
```
    The map the keys and values are stored in.
  - lastAccessedList
```
protected LinkedList<K extends Serializable> lastAccessedList
```
    Linked list to maintain order that cache objects are accessed in, most used to least used.
  - ageList
```
protected LinkedList<K extends Serializable> ageList
```
    Linked list to maintain time that cache objects were initially added to the cache, most recently added to oldest added.
  - maxLifetime
```
protected long maxLifetime
```
    Maximum length of time objects can exist in cache before expiring.
  - cacheHits
```
protected long cacheHits
```
    Maintain the number of cache hits and misses. A cache hit occurs every time the get method is called and the cache contains the requested object. A cache miss represents the opposite occurrence.
    Keeping track of cache hits and misses lets one measure how efficient the cache is; the higher the percentage of hits, the more efficient.
  - cacheMisses
```
protected long cacheMisses
```
    Maintain the number of cache hits and misses. A cache hit occurs every time the get method is called and the cache contains the requested object. A cache miss represents the opposite occurrence.
    Keeping track of cache hits and misses lets one measure how efficient the cache is; the higher the percentage of hits, the more efficient.
- Constructor Detail
  - DefaultCache
```
public DefaultCache(String name,
                    long maxSize,
                    long maxLifetime)
```
    Create a new default cache and specify the maximum size of for the cache in bytes, and the maximum lifetime of objects.
    
    Parameters:
    
    name - a name for the cache.
    
    maxSize - the maximum size of the cache in bytes. -1 means the cache has no max size.
    
    maxLifetime - the maximum amount of time objects can exist in cache before being deleted. -1 means objects never expire.
- Method Detail
  - put
```
public V put(K key,
             V value)
```
    Specified by:
    
    put in interface Map<K extends Serializable,V extends Serializable>
  - get
```
public V get(Object key)
```
    Specified by:
    
    get in interface Map<K extends Serializable,V extends Serializable>
  - remove
```
public V remove(Object key)
```
    Specified by:
    
    remove in interface Map<K extends Serializable,V extends Serializable>
  - clear
```
public void clear()
```
    Specified by:
    
    clear in interface Map<K extends Serializable,V extends Serializable>
  - size
```
public int size()
```
    Specified by:
    
    size in interface Map<K extends Serializable,V extends Serializable>
  - isEmpty
```
public boolean isEmpty()
```
    Specified by:
    
    isEmpty in interface Map<K extends Serializable,V extends Serializable>
  - values
```
public Collection<V> values()
```
    Specified by:
    
    values in interface Map<K extends Serializable,V extends Serializable>
  - containsKey
```
public boolean containsKey(Object key)
```
    Specified by:
    
    containsKey in interface Map<K extends Serializable,V extends Serializable>
  - putAll
```
public void putAll(Map<? extends K,? extends V> map)
```
    Specified by:
    
    putAll in interface Map<K extends Serializable,V extends Serializable>
  - containsValue
```
public boolean containsValue(Object value)
```
    Specified by:
    
    containsValue in interface Map<K extends Serializable,V extends Serializable>
  - entrySet
```
public Set<Map.Entry<K,V>> entrySet()
```
    Specified by:
    
    entrySet in interface Map<K extends Serializable,V extends Serializable>
  - keySet
```
public Set<K> keySet()
```
    Specified by:
    
    keySet in interface Map<K extends Serializable,V extends Serializable>
  - getName
```
public String getName()
```
    Returns the name of this cache. The name is completely arbitrary and used only for display to administrators.
    
    Specified by:
    
    getName in interface Cache<K extends Serializable,V extends Serializable>
    
    Returns:
    
    the name of this cache.
  - setName
```
public void setName(String name)
```
    Sets the name of this cache.
    
    Specified by:
    
    setName in interface Cache<K extends Serializable,V extends Serializable>
    
    Parameters:
    
    name - the name of this cache.
  - getCacheHits
```
public long getCacheHits()
```
    Returns the number of cache hits. A cache hit occurs every time the get method is called and the cache contains the requested object.
    Keeping track of cache hits and misses lets one measure how efficient the cache is; the higher the percentage of hits, the more efficient.
    
    Specified by:
    
    getCacheHits in interface Cache<K extends Serializable,V extends Serializable>
    
    Returns:
    
    the number of cache hits.
  - getCacheMisses
```
public long getCacheMisses()
```
    Returns the number of cache misses. A cache miss occurs every time the get method is called and the cache does not contain the requested object.
    Keeping track of cache hits and misses lets one measure how efficient the cache is; the higher the percentage of hits, the more efficient.
    
    Specified by:
    
    getCacheMisses in interface Cache<K extends Serializable,V extends Serializable>
    
    Returns:
    
    the number of cache hits.
  - getCacheSize
```
public int getCacheSize()
```
    Returns the size of the cache contents in bytes. This value is only a rough approximation, so cache users should expect that actual VM memory used by the cache could be significantly higher than the value reported by this method.
    
    Specified by:
    
    getCacheSize in interface Cache<K extends Serializable,V extends Serializable>
    
    Returns:
    
    the size of the cache contents in bytes.
  - getMaxCacheSize
```
public long getMaxCacheSize()
```
    Returns the maximum size of the cache (in bytes). If the cache grows larger than the max size, the least frequently used items will be removed. If the max cache size is set to -1, there is no size limit.
    
    Specified by:
    
    getMaxCacheSize in interface Cache<K extends Serializable,V extends Serializable>
    
    Returns:
    
    the maximum size of the cache (-1 indicates unlimited max size).
  - setMaxCacheSize
```
public void setMaxCacheSize(int maxCacheSize)
```
    Sets the maximum size of the cache. If the cache grows larger than the max size, the least frequently used items will be removed. If the max cache size is set to -1, there is no size limit.
    
    Specified by:
    
    setMaxCacheSize in interface Cache<K extends Serializable,V extends Serializable>
    
    Parameters:
    
    maxCacheSize - the maximum size of this cache (-1 indicates unlimited max size).
  - getMaxLifetime
```
public long getMaxLifetime()
```
    Returns the maximum number of milleseconds that any object can live in cache. Once the specified number of milleseconds passes, the object will be automatically expried from cache. If the max lifetime is set to -1, then objects never expire.
    
    Specified by:
    
    getMaxLifetime in interface Cache<K extends Serializable,V extends Serializable>
    
    Returns:
    
    the maximum number of milleseconds before objects are expired.
  - setMaxLifetime
```
public void setMaxLifetime(long maxLifetime)
```
    Sets the maximum number of milleseconds that any object can live in cache. Once the specified number of milleseconds passes, the object will be automatically expried from cache. If the max lifetime is set to -1, then objects never expire.
    
    Specified by:
    
    setMaxLifetime in interface Cache<K extends Serializable,V extends Serializable>
    
    Parameters:
    
    maxLifetime - the maximum number of milleseconds before objects are expired.
  - deleteExpiredEntries
```
protected void deleteExpiredEntries()
```
    Clears all entries out of cache where the entries are older than the maximum defined age.
  - cullCache
```
protected final void cullCache()
```
    Removes objects from cache if the cache is too full. "Too full" is defined as within 3% of the maximum cache size. Whenever the cache is is too big, the least frequently used elements are deleted until the cache is at least 10% empty.
  - getCacheCulls
```
public long getCacheCulls(Duration duration)
```

Class DefaultCache<K extends Serializable,V extends Serializable>

Nested Class Summary

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

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Field Detail

map

lastAccessedList

ageList

maxLifetime

cacheHits

cacheMisses

Constructor Detail

DefaultCache

Method Detail

put

get

remove

clear

size

isEmpty

values

containsKey

putAll

containsValue

entrySet

keySet

getName

setName

getCacheHits

getCacheMisses

getCacheSize

getMaxCacheSize

setMaxCacheSize

getMaxLifetime

setMaxLifetime

deleteExpiredEntries

cullCache

getCacheCulls