org.apache.xerces.util

Class SymbolHash

java.lang.Object

org.apache.xerces.util.SymbolHash

public class SymbolHash
extends Object

This class is an unsynchronized hash table primary used for String to Object mapping.

The hash code uses the same algorithm as SymbolTable class.

Version:

$Id$

Author:

Elena Litani

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	SymbolHash.Entry This class is a key table entry.

Field Summary

Fields

Modifier and Type	Field and Description
protected SymbolHash.Entry[]	fBuckets Buckets.
protected int[]	fHashMultipliers Array of randomly selected hash function multipliers or null if the default String.hashCode() function should be used.
protected int	fNum Number of elements.
protected int	fTableSize Actual table size
protected static int	MAX_HASH_COLLISIONS Maximum hash collisions per bucket.
protected static int	MULTIPLIERS_MASK
protected static int	MULTIPLIERS_SIZE
protected static int	TABLE_SIZE Default table size.

Constructor Summary

Constructors

Constructor and Description
SymbolHash() Constructs a key table with the default size.
SymbolHash(int size) Constructs a key table with a given size.

Method Summary

Modifier and Type	Method and Description
void	clear() Remove all key/value association.
Object	get(Object key) Get the value associated with the given key.
Object[]	getEntries() Return key/value pairs of all entries in the map
int	getLength() Get the number of key/value pairs stored in this table.
int	getValues(Object[] elements, int from) Add all values to the given array.
protected int	hash(Object key) Returns a hashcode value for the specified key.
SymbolHash	makeClone() Make a clone of this object.
void	put(Object key, Object value) Adds the key/value mapping to the key table.
protected void	rebalance() Randomly selects a new hash function and reorganizes this SymbolHash in order to more evenly distribute its entries across the table.
protected void	rehash() Increases the capacity of and internally reorganizes this SymbolHash, in order to accommodate and access its entries more efficiently.
protected SymbolHash.Entry	search(Object key, int bucket)

Methods inherited from class java.lang.Object

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

Field Detail

TABLE_SIZE

protected static final int TABLE_SIZE

Default table size.

See Also:

Constant Field Values

MAX_HASH_COLLISIONS

protected static final int MAX_HASH_COLLISIONS

Maximum hash collisions per bucket.

See Also:

Constant Field Values

MULTIPLIERS_SIZE

protected static final int MULTIPLIERS_SIZE

See Also:

Constant Field Values

MULTIPLIERS_MASK

protected static final int MULTIPLIERS_MASK

See Also:

Constant Field Values

fTableSize

protected int fTableSize

Actual table size

fBuckets

protected SymbolHash.Entry[] fBuckets

Buckets.

fNum

protected int fNum

Number of elements.

fHashMultipliers

protected int[] fHashMultipliers

Array of randomly selected hash function multipliers or null if the default String.hashCode() function should be used.

Constructor Detail

SymbolHash

public SymbolHash()

Constructs a key table with the default size.

SymbolHash

public SymbolHash(int size)

Constructs a key table with a given size.

Parameters:

size - the size of the key table.

Method Detail

put

public void put(Object key,
                Object value)

Adds the key/value mapping to the key table. If the key already exists, the previous value associated with this key is overwritten by the new value.

Parameters:

key -

value -

get

public Object get(Object key)

Get the value associated with the given key.

Parameters:

key -

Returns:

the value associated with the given key.

getLength

public int getLength()

Get the number of key/value pairs stored in this table.

Returns:

the number of key/value pairs stored in this table.

getValues

public int getValues(Object[] elements,
                     int from)

Add all values to the given array. The array must have enough entry.

Parameters:

elements - the array to store the elements

from - where to start store element in the array

Returns:

number of elements copied to the array

getEntries

public Object[] getEntries()

Return key/value pairs of all entries in the map

makeClone

public SymbolHash makeClone()

Make a clone of this object.

clear

public void clear()

Remove all key/value association. This tries to save a bit of GC'ing by at least keeping the fBuckets array around.

search

protected SymbolHash.Entry search(Object key,
                                  int bucket)

hash

protected int hash(Object key)

Returns a hashcode value for the specified key.

Parameters:

key - The key to hash.

rehash

protected void rehash()

Increases the capacity of and internally reorganizes this SymbolHash, in order to accommodate and access its entries more efficiently. This method is called automatically when the number of keys in the SymbolHash exceeds its number of buckets.

rebalance

protected void rebalance()

Randomly selects a new hash function and reorganizes this SymbolHash in order to more evenly distribute its entries across the table. This method is called automatically when the number keys in one of the SymbolHash's buckets exceeds MAX_HASH_COLLISIONS.