oracle.javatools.util
Class Maps.CacheStrategy<K,V>

java.lang.Object
  oracle.javatools.util.Maps.CacheStrategy<K,V>

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

Maps.BoundedLruCacheStrategy, Maps.UnboundedCacheStrategy

Enclosing class:

Maps

public abstract static class Maps.CacheStrategy<K,V>
extends java.lang.Object
implements java.io.Serializable

An abstract caching strategy for a cache map.

Implementations override one or more methods of this class to configure the cache map, to track its contents, and to evict stale values.

Implementations can configure the following immutable properties of the cache map:

• the initial capacity;
• the load factor;
• the type of reference used for values, strong, soft, or weak;
• whether the map maintains a canonical mapping, narrowly defined here to mean whether, for a given key, the map will always return the same value so long as a reference to the value is held outside the map.

Two methods that are of particular use in implementing an eviction strategy are Maps.CacheMap.getEldestEntry() and Maps.CacheMap.evictEntry(oracle.javatools.util.Maps.LinkedEntry).

See Also:

Serialized Form

Field Summary

static Maps.CacheMap.Canonicity	CANONICAL
static int	DEFAULT_INITIAL_CAPACITY
static float	DEFAULT_LOAD_FACTOR
static Maps.CacheMap.Strength	HARD Deprecated. Use STRONG.
static Maps.CacheMap.Canonicity	NONCANONICAL Deprecated. Use NOT_CANONICAL.
static Maps.CacheMap.Canonicity	NOT_CANONICAL
static Maps.CacheMap.Strength	SOFT
static Maps.CacheMap.Strength	STRONG
static Maps.CacheMap.Strength	WEAK

Constructor Summary

protected

Maps.CacheStrategy(int initialCapacity, float loadFactor, Maps.CacheMap.Canonicity canonicity, Maps.CacheMap.Strength defaultStrength) Constructs a cache strategy.

Method Summary

protected Maps.LinkedEntry<K,V>	createDefaultEntry(int hashCode, K key, V value, Maps.LinkedEntry<K,V> next)
protected Maps.LinkedEntry<K,V>	createEntry(int hashCode, K key, V value, Maps.LinkedEntry<K,V> next, java.lang.ref.ReferenceQueue<V> queue)
protected Maps.LinkedEntry<K,V>	createEvictedEntry(int hashCode, K key, V value, Maps.LinkedEntry<K,V> next, java.lang.ref.ReferenceQueue<V> queue)
protected Maps.LinkedEntry<K,V>	createSoftEntry(int hashCode, K key, V value, Maps.LinkedEntry<K,V> next, java.lang.ref.ReferenceQueue<V> queue)
protected Maps.LinkedEntry<K,V>	createWeakEntry(int hashCode, K key, V value, Maps.LinkedEntry<K,V> next, java.lang.ref.ReferenceQueue<V> queue)
protected void	entryAccessed(Maps.CacheMap<K,V> map, Maps.LinkedEntry<K,V> entry) Invoked when the value of an existing entry is accessed by Maps.AbstractHashMap.get(java.lang.Object).
protected void	entryAdded(Maps.CacheMap<K,V> map, Maps.LinkedEntry<K,V> entry) Invoked when a new entry is added to this map, when entries are added by Maps.AbstractHashMap.put(K, V).
protected void	entryChanged(Maps.CacheMap<K,V> map, Maps.LinkedEntry<K,V> oldEntry, V oldValue, Maps.LinkedEntry<K,V> newEntry) Invoked when the value of an existing entry is changed or when entries are changed by Maps.AbstractHashMap.put(K, V).
protected void	entryEvicted(Maps.CacheMap<K,V> map, Maps.LinkedEntry<K,V> entry) Invoked when an existing entry is evicted by Maps.AbstractLinkedHashMap.evictEntry(E).
protected void	entryPurged(Maps.CacheMap<K,V> map, Maps.LinkedEntry<K,V> entry) Invoked when an existing entry is purged after its value has been garbage collected.
protected void	entryRemoved(Maps.CacheMap<K,V> map, Maps.LinkedEntry<K,V> entry) Invoked when an existing entry is removed by a remove method of this map, of a view collection of this map, or of an iterator of a view collection of this map The Maps.CacheMap implementation never invokes entryRemoved(oracle.javatools.util.Maps.CacheMap, oracle.javatools.util.Maps.LinkedEntry) when entries are removed by the Maps.CacheMap.clear() method of this map, or of a view collection of this map.
Maps.CacheMap.Canonicity	getCanonicity() Gets whether the cache maps canonically.
Maps.CacheMap.Strength	getDefaultStrength() Gets the value reference type of the cache map.
int	getInitialCapacity() Gets the initial capacity of the cache map.
float	getLoadFactor() Gets the load factor of the cache map.
protected void	mapChanged(Maps.CacheMap<K,V> map) Invoked when the map has changed, when entries are added, removed, or accessed.
protected void	mapConstructed(Maps.CacheMap<K,V> map) Invoked when the map has constructed.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_INITIAL_CAPACITY

public static final int DEFAULT_INITIAL_CAPACITY

See Also:

Constant Field Values

DEFAULT_LOAD_FACTOR

public static final float DEFAULT_LOAD_FACTOR

See Also:

Constant Field Values

STRONG

public static final Maps.CacheMap.Strength STRONG

SOFT

public static final Maps.CacheMap.Strength SOFT

WEAK

public static final Maps.CacheMap.Strength WEAK

HARD

public static final Maps.CacheMap.Strength HARD

Deprecated. Use STRONG.

CANONICAL

public static final Maps.CacheMap.Canonicity CANONICAL

NOT_CANONICAL

public static final Maps.CacheMap.Canonicity NOT_CANONICAL

NONCANONICAL

public static final Maps.CacheMap.Canonicity NONCANONICAL

Deprecated. Use NOT_CANONICAL.

Constructor Detail

Maps.CacheStrategy

protected Maps.CacheStrategy(int initialCapacity,
                             float loadFactor,
                             Maps.CacheMap.Canonicity canonicity,
                             Maps.CacheMap.Strength defaultStrength)

Constructs a cache strategy.

Method Detail

getInitialCapacity

public int getInitialCapacity()

Gets the initial capacity of the cache map.

getLoadFactor

public float getLoadFactor()

Gets the load factor of the cache map.

getCanonicity

public Maps.CacheMap.Canonicity getCanonicity()

Gets whether the cache maps canonically.

getDefaultStrength

public Maps.CacheMap.Strength getDefaultStrength()

Gets the value reference type of the cache map.

createEntry

protected Maps.LinkedEntry<K,V> createEntry(int hashCode,
                                            K key,
                                            V value,
                                            Maps.LinkedEntry<K,V> next,
                                            java.lang.ref.ReferenceQueue<V> queue)

The Maps.CacheMap implementation delegates to createDefaultEntry(int, K, V, oracle.javatools.util.Maps.LinkedEntry), createSoftEntry(int, K, V, oracle.javatools.util.Maps.LinkedEntry, java.lang.ref.ReferenceQueue), or createWeakEntry(int, K, V, oracle.javatools.util.Maps.LinkedEntry, java.lang.ref.ReferenceQueue) as indicated by getDefaultStrength().

createDefaultEntry

protected Maps.LinkedEntry<K,V> createDefaultEntry(int hashCode,
                                                   K key,
                                                   V value,
                                                   Maps.LinkedEntry<K,V> next)

createSoftEntry

protected Maps.LinkedEntry<K,V> createSoftEntry(int hashCode,
                                                K key,
                                                V value,
                                                Maps.LinkedEntry<K,V> next,
                                                java.lang.ref.ReferenceQueue<V> queue)

createWeakEntry

protected Maps.LinkedEntry<K,V> createWeakEntry(int hashCode,
                                                K key,
                                                V value,
                                                Maps.LinkedEntry<K,V> next,
                                                java.lang.ref.ReferenceQueue<V> queue)

createEvictedEntry

protected Maps.LinkedEntry<K,V> createEvictedEntry(int hashCode,
                                                   K key,
                                                   V value,
                                                   Maps.LinkedEntry<K,V> next,
                                                   java.lang.ref.ReferenceQueue<V> queue)

mapConstructed

protected void mapConstructed(Maps.CacheMap<K,V> map)

Invoked when the map has constructed.

The Maps.CacheStrategy implementation does nothing.

mapChanged

protected void mapChanged(Maps.CacheMap<K,V> map)

Invoked when the map has changed, when entries are added, removed, or accessed. This method is invoked before the associated entryAdded(oracle.javatools.util.Maps.CacheMap, oracle.javatools.util.Maps.LinkedEntry), entryRemoved(oracle.javatools.util.Maps.CacheMap, oracle.javatools.util.Maps.LinkedEntry), or entryAccessed(oracle.javatools.util.Maps.CacheMap, oracle.javatools.util.Maps.LinkedEntry) method is invoked.

The Maps.CacheStrategy implementation does nothing.

entryAdded

protected void entryAdded(Maps.CacheMap<K,V> map,
                          Maps.LinkedEntry<K,V> entry)

Invoked when a new entry is added to this map, when entries are added by Maps.AbstractHashMap.put(K, V).

The Maps.CacheStrategy implementation does nothing.

entryChanged

protected void entryChanged(Maps.CacheMap<K,V> map,
                            Maps.LinkedEntry<K,V> oldEntry,
                            V oldValue,
                            Maps.LinkedEntry<K,V> newEntry)

Invoked when the value of an existing entry is changed or when entries are changed by Maps.AbstractHashMap.put(K, V).

If the entry to change was mutable, its value is changed with Map.Entry#setValue and oldEntry and newEntry are the same object. If the entry to change was not mutable, a new entry must be created and oldEntry and newEntry are different objects.

When a client directly invokes the Map.Entry#setValue method of any of the Map.Entry implementations provided in this class, this method is not invoked (while this could be addressed, it would require each entry instance to hold a reference to its map).

The Maps.CacheStrategy implementation does nothing.

Parameters:

oldEntry - The existing entry that changed.

oldValue - The old value of the entry.

newEntry - The new entry, which may be the same as the old.

entryAccessed

protected void entryAccessed(Maps.CacheMap<K,V> map,
                             Maps.LinkedEntry<K,V> entry)

Invoked when the value of an existing entry is accessed by Maps.AbstractHashMap.get(java.lang.Object). Access to an entry by iterating a view collection of this map does not cause this method to be invoked.

The Maps.CacheStrategy implementation does nothing.

entryRemoved

protected void entryRemoved(Maps.CacheMap<K,V> map,
                            Maps.LinkedEntry<K,V> entry)

Invoked when an existing entry is removed by a remove method of this map, of a view collection of this map, or of an iterator of a view collection of this map

The Maps.CacheMap implementation never invokes entryRemoved(oracle.javatools.util.Maps.CacheMap, oracle.javatools.util.Maps.LinkedEntry) when entries are removed by the Maps.CacheMap.clear() method of this map, or of a view collection of this map.

The Maps.CacheStrategy implementation does nothing.

entryPurged

protected void entryPurged(Maps.CacheMap<K,V> map,
                           Maps.LinkedEntry<K,V> entry)

Invoked when an existing entry is purged after its value has been garbage collected.

The Maps.CacheMap implementation only ever invokes entryPurged(oracle.javatools.util.Maps.CacheMap, oracle.javatools.util.Maps.LinkedEntry) for entries which extend SoftReference or WeakReference and which register themselves with the ReferenceQueue returned by Maps.AbstractHashMap.getQueue(). Maps provides four such classes: Maps.SoftEntry, Maps.WeakEntry, Maps.SoftLinkedEntry, and Maps.WeakLinkedEntry.

The Maps.CacheStrategy implementation does nothing.

entryEvicted

protected void entryEvicted(Maps.CacheMap<K,V> map,
                            Maps.LinkedEntry<K,V> entry)

Invoked when an existing entry is evicted by Maps.AbstractLinkedHashMap.evictEntry(E).

If this map is canonical, eviction means the entry was converted to a weak reference and mapChanged(oracle.javatools.util.Maps.CacheMap) was not invoked. If the map is not canonical, eviction means the entry was removed and mapChanged(oracle.javatools.util.Maps.CacheMap) was invoked.

The Maps.CacheStrategy implementation does nothing.