org.hd.d.pg2k.svrCore
Class MemoryTools.SimpleLRUMap<K,V>

java.lang.Object
  org.hd.d.pg2k.svrCore.MemoryTools.SimpleLRUMap<K,V>

Enclosing class:

MemoryTools

public static final class MemoryTools.SimpleLRUMap<K,V>
extends java.lang.Object

Simplified thread-safe map with fixed capacity that discards excess items in LRU (Least Recently Used) order. This provides a map with a fixed upper size. Attempts to insert more items than the capacity will result in old items being removed in LRU order, thus leaving the newest items in the cache.

Each put() or get() makes its key/value pair the most-recently used and thus the last to be removed from the map of current key/value pairs when a series of put()s forces the map to overflow.

Thread-safe.

A lock can be held on instances of this object to make compound operations atomic.

Does not support the full Map interface.

defaultLoadFactor

private static final float defaultLoadFactor

Default load factor.

See Also:

Constant Field Values

lhm

private final java.util.LinkedHashMap<K,V> lhm

Underlying (non-thread-safe) LinkedHashMap on which this is based; never null.

name

private final java.lang.String name

Optional name for diagnostics; can be null.

MemoryTools.SimpleLRUMap

public MemoryTools.SimpleLRUMap(int maxCapacity,
                                java.lang.String name)

Create an instance with given (positive) maximum size and the default load factor.

MemoryTools.SimpleLRUMap

public MemoryTools.SimpleLRUMap(int maxCapacity,
                                float loadFactor,
                                java.lang.String name)

Create an instance with given (positive) maximum size and load factor.

get

public V get(K key)

Get an entry from the map, making it the Most Recently Used; null if no such element.

put

public V put(K key,
             V value)

Put an entry in the map, making it the Most Recently Used, returning previous value if any.

remove

public V remove(K key)

Remove an entry from the map and return the removed value, if any, else null.

clear

public void clear()

Clear the map.

getCopy

public java.util.Map<K,V> getCopy()

Take a copy of the map contents, which does not alter LRU; never null.

size

public int size()

Return the number of entries in the map; non-negative.

toString

public java.lang.String toString()

Provide a human-readable summary of status. Useful for debugging/tuning, for example.

Overrides:

toString in class java.lang.Object