org.ka2ddo.util

Class ShareableObjectCache<T>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractSet<T>

org.ka2ddo.util.ShareableObjectCache<T>

All Implemented Interfaces:

java.lang.Iterable<T>, java.util.Collection<T>, java.util.Set<T>

Direct Known Subclasses:

StringCache

public abstract class ShareableObjectCache<T>
extends java.util.AbstractSet<T>

This class provides an alternative to the Java PermGen heap section used for String.intern(), such that applications won't run out of Java PermGen space while still being able to share constant object declarations.

Author:

Andrew Pavlin, KA2DDO

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ShareableObjectCache() Constructs a new, empty ShareableObjectCache with the default initial capacity and load factor.
protected	ShareableObjectCache(int initialCapacity) Constructs a new, empty ShareableObjectCache with the given initial capacity and the default load factor (2.0).
protected	ShareableObjectCache(int initialCapacity, float loadFactor) Constructs a new, empty ShareableObjectCache with the given initial capacity and the given load factor.

Method Summary

Modifier and Type	Method and Description
boolean	add(T key) Associates the specified value with the specified key in this map.
void	clear() Removes all of the mappings from this map.
protected abstract java.lang.Class<?>	getType() Get data type of the objects stored in this ShareableObjectCache.
T	internKey(T t) Look for the specified key in the cache.
boolean	isEmpty() Returns true if this set contains no entries.
java.util.Iterator<T>	iterator() Returns an iterator over the elements contained in this collection.
boolean	remove(java.lang.Object key) Removes the entry for a key from this cache if it is present.
int	size() Returns the number of key-value mappings in this map.
java.lang.String	toString() Returns a string description of this collection.

Methods inherited from class java.util.AbstractSet

equals, hashCode, removeAll

Methods inherited from class java.util.AbstractCollection

addAll, contains, containsAll, retainAll, toArray, toArray

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Set

addAll, contains, containsAll, retainAll, spliterator, toArray, toArray

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

ShareableObjectCache

protected ShareableObjectCache(int initialCapacity,
                               float loadFactor)

Constructs a new, empty ShareableObjectCache with the given initial capacity and the given load factor.

Parameters:

initialCapacity - The initial capacity of the ShareableObjectCache

loadFactor - The load factor of the ShareableObjectCache

Throws:

java.lang.IllegalArgumentException - if the initial capacity is negative, or if the load factor is nonpositive.

ShareableObjectCache

protected ShareableObjectCache(int initialCapacity)

Constructs a new, empty ShareableObjectCache with the given initial capacity and the default load factor (2.0).

Parameters:

initialCapacity - The initial capacity of the ShareableObjectCache

Throws:

java.lang.IllegalArgumentException - if the initial capacity is negative

ShareableObjectCache

protected ShareableObjectCache()

Constructs a new, empty ShareableObjectCache with the default initial capacity and load factor.

Method Detail

size

public int size()

Returns the number of key-value mappings in this map. This result is a snapshot, and may not reflect unprocessed entries that will be removed before next attempted access because they are no longer referenced.

Specified by:

size in interface java.util.Collection<T>

Specified by:

size in interface java.util.Set<T>

Specified by:

size in class java.util.AbstractCollection<T>

isEmpty

public boolean isEmpty()

Returns true if this set contains no entries. This result is a snapshot, and may not reflect unprocessed entries that will be removed before next attempted access because they are no longer referenced.

Specified by:

isEmpty in interface java.util.Collection<T>

Specified by:

isEmpty in interface java.util.Set<T>

Overrides:

isEmpty in class java.util.AbstractCollection<T>

add

public boolean add(T key)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is preserved (since it is a duplicate, by the definition and purpose of this class).

Specified by:

add in interface java.util.Collection<T>

Specified by:

add in interface java.util.Set<T>

Overrides:

add in class java.util.AbstractCollection<T>

Parameters:

key - key with which the specified value is to be associated.

Returns:

boolean true if this was a new entry in the cache

internKey

public T internKey(T t)

Look for the specified key in the cache.

Parameters:

t - T hashable object

Returns:

cached equal-value of t (or t itself if never listed in cache before)

remove

public boolean remove(java.lang.Object key)

Removes the entry for a key from this cache if it is present. More formally, if this cache contains an entry for key k such that (key==null ? k==null : key.equals(k)), that mapping is removed. (The map can contain at most one such mapping.)

Returns the value to which this map previously associated the key, or null if the map contained no mapping for the key. A return value of null does not necessarily indicate that the map contained no mapping for the key; it's also possible that the map explicitly mapped the key to null.

The map will not contain a mapping for the specified key once the call returns.

Specified by:

remove in interface java.util.Collection<T>

Specified by:

remove in interface java.util.Set<T>

Overrides:

remove in class java.util.AbstractCollection<T>

Parameters:

key - key whose mapping is to be removed from the map

Returns:

boolean true if an entry formerly existed matching the key

clear

public void clear()

Removes all of the mappings from this map. The map will be empty after this call returns.

Specified by:

clear in interface java.util.Collection<T>

Specified by:

clear in interface java.util.Set<T>

Overrides:

clear in class java.util.AbstractCollection<T>

getType

protected abstract java.lang.Class<?> getType()

Get data type of the objects stored in this ShareableObjectCache.

Returns:

Class of stored objects

toString

public java.lang.String toString()

Returns a string description of this collection.

Overrides:

toString in class java.util.AbstractCollection<T>

Returns:

a string description of this collection

iterator

public java.util.Iterator<T> iterator()

Returns an iterator over the elements contained in this collection.

Specified by:

iterator in interface java.lang.Iterable<T>

Specified by:

iterator in interface java.util.Collection<T>

Specified by:

iterator in interface java.util.Set<T>

Specified by:

iterator in class java.util.AbstractCollection<T>

Returns:

an iterator over the elements contained in this collection