mondrian.util
Class ObjectPool<T>

java.lang.Object
  mondrian.util.ObjectPool<T>

public class ObjectPool<T>
extends Object

An ObjectPool is a low-memory replacement for a HashSet. A HashSet contains a HashMap which in turn has an array of Entry objects, the Entry objects themselves, and the key and value objects. An ObjectPool has simply an array of objects and the objects themselves which server as both key and value.

This is like the String intern method, but works for an Object type and whereas the String intern method is global an ObjectPool can be used within a context and then garbage collected. Objects can not removed from an ObjectPool except by calling the clear method which removes all objects.

Just as with a HashSet's key objects, objects to be placed into an ObjectPool must implement the equals and hashCode methods.

This implementation is NOT thread safe.

Author:

Richard Emberson

Field Summary

protected static int	DEFAULT_CAPACITY
protected static double	DEFAULT_MAX_LOAD_FACTOR
protected static double	DEFAULT_MIN_LOAD_FACTOR
protected int	distinct The number of distinct associations in the map; its "size()".
protected static byte	FREE
protected int	freeEntries The number of table entries in state==FREE.
protected static byte	FULL
protected int	highWaterMark
protected double	maxLoadFactor The maximum load factor for the hashtable.
protected double	minLoadFactor The minimum load factor for the hashtable.
protected T[]	values

Constructor Summary

ObjectPool()

ObjectPool(int initialCapacity)

ObjectPool(int initialCapacity, double minLoadFactor, double maxLoadFactor)

Method Summary

T	add(T key) Adds an object to the ObjectPool if it is not already in the pool or returns the object that is already in the pool that matches the object being added.
protected int	chooseGrowCapacity(int size, double minLoad, double maxLoad)
protected int	chooseHighWaterMark(int capacity, double maxLoad)
protected int	chooseLowWaterMark(int capacity, double minLoad)
void	clear() Removes all objects from the pool but keeps the current size of the internal storage.
boolean	contains(T key) Returns true it the Object is already in the ObjectPool and false otherwise.
protected boolean	equals(T t, T key)
protected int	hash(T key)
protected int	indexOfInsertion(T key)
Iterator<T>	iterator() Returns an Iterator of this ObjectPool.
protected int	nextPrime(int desiredCapacity)
protected void	rehash(int newCapacity)
protected void	setUp(int initialCapacity, double minLoadFactor, double maxLoadFactor)
int	size() Return the number of entries in the ObjectPool.
void	trimToSize() Reduce the size of the internal arrays to a size just big enough to hold the current set of entries.

Methods inherited from class java.lang.Object

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

Field Detail

FREE

protected static final byte FREE

See Also:

Constant Field Values

FULL

protected static final byte FULL

See Also:

Constant Field Values

DEFAULT_CAPACITY

protected static final int DEFAULT_CAPACITY

See Also:

Constant Field Values

DEFAULT_MIN_LOAD_FACTOR

protected static final double DEFAULT_MIN_LOAD_FACTOR

See Also:

Constant Field Values

DEFAULT_MAX_LOAD_FACTOR

protected static final double DEFAULT_MAX_LOAD_FACTOR

See Also:

Constant Field Values

distinct

protected int distinct

The number of distinct associations in the map; its "size()".

highWaterMark

protected int highWaterMark

minLoadFactor

protected double minLoadFactor

The minimum load factor for the hashtable.

maxLoadFactor

protected double maxLoadFactor

The maximum load factor for the hashtable.

values

protected T[] values

freeEntries

protected int freeEntries

The number of table entries in state==FREE.

Constructor Detail

ObjectPool

public ObjectPool()

ObjectPool

public ObjectPool(int initialCapacity)

ObjectPool

public ObjectPool(int initialCapacity,
                  double minLoadFactor,
                  double maxLoadFactor)

Method Detail

size

public int size()

Return the number of entries in the ObjectPool.

Returns:

number of entries.

trimToSize

public void trimToSize()

Reduce the size of the internal arrays to a size just big enough to hold the current set of entries. Generally, this should only be called after all entries have been added. Calling this causes a new, smaller array to be allocated, the objects are copied to the new array and then the old array is free to be garbage collected; there is a small time when both arrays are in memory.

contains

public boolean contains(T key)

Returns true it the Object is already in the ObjectPool and false otherwise.

Parameters:

key - Object to test if member already or not.

Returns:

true is already member

add

public T add(T key)

Adds an object to the ObjectPool if it is not already in the pool or returns the object that is already in the pool that matches the object being added.

Parameters:

key - Object to add to pool

Returns:

Equivalent object, if it exists, otherwise key

clear

public void clear()

Removes all objects from the pool but keeps the current size of the internal storage.

iterator

public Iterator<T> iterator()

Returns an Iterator of this ObjectPool. The order of the Objects returned by the Iterator can not be counted on to be in the same order as they were inserted into the ObjectPool. The Iterator returned does not support the removal of ObjectPool members.

chooseGrowCapacity

protected int chooseGrowCapacity(int size,
                                 double minLoad,
                                 double maxLoad)

chooseHighWaterMark

protected final int chooseHighWaterMark(int capacity,
                                        double maxLoad)

chooseLowWaterMark

protected final int chooseLowWaterMark(int capacity,
                                       double minLoad)

nextPrime

protected int nextPrime(int desiredCapacity)

setUp

protected void setUp(int initialCapacity,
                     double minLoadFactor,
                     double maxLoadFactor)

hash

protected int hash(T key)

equals

protected boolean equals(T t,
                         T key)

indexOfInsertion

protected int indexOfInsertion(T key)

rehash

protected void rehash(int newCapacity)