wt.util
Class Cache

java.lang.Object
  java.util.AbstractMap
      wt.util.Cache

All Implemented Interfaces:

Map

public class Cache
extends AbstractMap

A fixed size, most recently used object cache. The caches size is set at construction, and only the most recently used entries are maintained. Each get or put operation makes that entry the most recently used. When putting new entries, if the cache is full, the least recently used entry is aged out of the cache.

Supported API: true
Extendable: false

Nested Class Summary

protected class

wt.util.Cache.CacheEntry Default implementation of Map.Entry

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

Map.Entry<K,V>

Constructor Summary

Cache(int size)
Construct a new fixed-size, most-recently-used cache.

Method Summary

void	clear() Clears the cache.
Enumeration	entries() Deprecated. Replaced by values().iterator() Supported API: true
Object	get(Object key) Get an entry from the cache.
Object	getAndRemove(Object key) Deprecated. Replaced by remove(Object) Supported API: true
Object	getAndReplace(Object key, Object value) Deprecated. Replaced by put(Object,Object) Supported API: true
Object	put(Object key, Object value) Put an entry in the cache.
Object	remove(Object key) Remove an entry from the cache.
String	toString() Returns string representation of the cache.

Methods inherited from class java.util.AbstractMap

clone, equals, hashCode, isEmpty, putAll, values

Methods inherited from class java.lang.Object

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

Constructor Detail

Cache

public Cache(int size)

Construct a new fixed-size, most-recently-used cache. Sparse arrays of ints are used to maintain linked lists in a memory efficient manner - the maximum size supported by this implementation is 715827882.

Supported API: true

Parameters:

size - the maximum number of entries stored in the cache.

Method Detail

get

public Object get(Object key)

Get an entry from the cache. Hit and miss statistics are updated.

Supported API: true

Specified by:

get in interface Map

Overrides:

get in class AbstractMap

Parameters:

key - the entry key

Returns:

the cached object or null if not found

put

public Object put(Object key,
                  Object value)

Put an entry in the cache. If an entry for the given key already exists, the previous value is discarded. This entry is considered the most recently used.

Supported API: true

Specified by:

put in interface Map

Overrides:

put in class AbstractMap

Parameters:

key - the entry key

value - the value to associate with the given key

Returns:

The previous value that mapped to the key, or null if there was no previous value

getAndReplace

public Object getAndReplace(Object key,
                            Object value)

Deprecated. Replaced by put(Object,Object)

Supported API: true

Get an entry from the cache and replace it with a new entry. The new entry is considered the most recently used. Hit and miss statistics are updated.

Parameters:

key - the entry key

value - the value to associate with the given key

Returns:

previous value

remove

public Object remove(Object key)

Remove an entry from the cache. Does nothing if the entry is not currently in the cache.

Supported API: true

Specified by:

remove in interface Map

Overrides:

remove in class AbstractMap

Parameters:

key - the entry key

getAndRemove

public Object getAndRemove(Object key)

Deprecated. Replaced by remove(Object)

Supported API: true

Get an entry from the cache and remove it at the same time. Does nothing if the entry is not currently in the cache. Hit and miss statistics are updated.

Parameters:

key - the entry key

Returns:

previous value

clear

public void clear()

Clears the cache. All entries are removed.

Supported API: true

Specified by:

clear in interface Map

Overrides:

clear in class AbstractMap

entries

public Enumeration entries()

Deprecated. Replaced by values().iterator()

Supported API: true

Returns an Enumeration of the values in the cache.

toString

public String toString()

Returns string representation of the cache. The string contains the default string representation of the object plus a summary of the current cache size, hits and misses counts, and aged out entry count.

Supported API: true

Overrides:

toString in class AbstractMap