org.apache.xerces.util

Class SoftReferenceSymbolTable

java.lang.Object

org.apache.xerces.util.SymbolTable

org.apache.xerces.util.SoftReferenceSymbolTable

public class SoftReferenceSymbolTable
extends SymbolTable

This symbol table uses SoftReferences to its String entries, which means that table entries that have no references to them can be garbage collected when memory is needed. Thus, in documents with very very large numbers of unique strings, using this SymbolTable will prevent an out of memory error from occurring.

Version:

$Id: SoftReferenceSymbolTable.java 1358350 2012-07-06 19:04:35Z mrglavas $

Author:

Peter McCracken, IBM

See Also:

SymbolTable

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	SoftReferenceSymbolTable.SREntry This class is a symbol table entry.
protected static class	SoftReferenceSymbolTable.SREntryData

Nested classes/interfaces inherited from class org.apache.xerces.util.SymbolTable

SymbolTable.Entry

Field Summary

Fields

Modifier and Type	Field and Description
protected SoftReferenceSymbolTable.SREntry[]	fBuckets

Fields inherited from class org.apache.xerces.util.SymbolTable

fCollisionThreshold, fCount, fHashMultipliers, fLoadFactor, fTableSize, fThreshold, MAX_HASH_COLLISIONS, MULTIPLIERS_MASK, MULTIPLIERS_SIZE, TABLE_SIZE

Constructor Summary

Constructors

Constructor and Description
SoftReferenceSymbolTable() Constructs a new, empty SymbolTable with a default initial capacity (101) and load factor, which is 0.75.
SoftReferenceSymbolTable(int initialCapacity) Constructs a new, empty SymbolTable with the specified initial capacity and default load factor, which is 0.75.
SoftReferenceSymbolTable(int initialCapacity, float loadFactor) Constructs a new, empty SymbolTable with the specified initial capacity and the specified load factor.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.String	addSymbol(char[] buffer, int offset, int length) Adds the specified symbol to the symbol table and returns a reference to the unique symbol.
java.lang.String	addSymbol(java.lang.String symbol) Adds the specified symbol to the symbol table and returns a reference to the unique symbol.
protected void	compact() Reduces the capacity of and internally reorganizes this SymbolTable, in order to accommodate and access its entries in a more memory efficient way.
boolean	containsSymbol(char[] buffer, int offset, int length) Returns true if the symbol table already contains the specified symbol.
boolean	containsSymbol(java.lang.String symbol) Returns true if the symbol table already contains the specified symbol.
protected void	rebalance() Randomly selects a new hash function and reorganizes this SymbolTable in order to more evenly distribute its entries across the table.
protected void	rehash() Increases the capacity of and internally reorganizes this SymbolTable, in order to accommodate and access its entries more efficiently.

Methods inherited from class org.apache.xerces.util.SymbolTable

hash, hash

Methods inherited from class java.lang.Object

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

Field Detail

fBuckets

protected SoftReferenceSymbolTable.SREntry[] fBuckets

Constructor Detail

SoftReferenceSymbolTable

public SoftReferenceSymbolTable(int initialCapacity,
                        float loadFactor)

Constructs a new, empty SymbolTable with the specified initial capacity and the specified load factor.

Parameters:

initialCapacity - the initial capacity of the SymbolTable.

loadFactor - the load factor of the SymbolTable.

Throws:

java.lang.IllegalArgumentException - if the initial capacity is less than zero, or if the load factor is nonpositive.

SoftReferenceSymbolTable

public SoftReferenceSymbolTable(int initialCapacity)

Constructs a new, empty SymbolTable with the specified initial capacity and default load factor, which is 0.75.

Parameters:

initialCapacity - the initial capacity of the hashtable.

Throws:

java.lang.IllegalArgumentException - if the initial capacity is less than zero.

SoftReferenceSymbolTable

public SoftReferenceSymbolTable()

Constructs a new, empty SymbolTable with a default initial capacity (101) and load factor, which is 0.75.

Method Detail

addSymbol

public java.lang.String addSymbol(java.lang.String symbol)

Adds the specified symbol to the symbol table and returns a reference to the unique symbol. If the symbol already exists, the previous symbol reference is returned instead, in order guarantee that symbol references remain unique.

Overrides:

addSymbol in class SymbolTable

Parameters:

symbol - The new symbol.

addSymbol

public java.lang.String addSymbol(char[] buffer,
                         int offset,
                         int length)

Adds the specified symbol to the symbol table and returns a reference to the unique symbol. If the symbol already exists, the previous symbol reference is returned instead, in order guarantee that symbol references remain unique.

Overrides:

addSymbol in class SymbolTable

Parameters:

buffer - The buffer containing the new symbol.

offset - The offset into the buffer of the new symbol.

length - The length of the new symbol in the buffer.

rehash

protected void rehash()

Increases the capacity of and internally reorganizes this SymbolTable, in order to accommodate and access its entries more efficiently. This method is called automatically when the number of keys in the SymbolTable exceeds this hashtable's capacity and load factor.

Overrides:

rehash in class SymbolTable

compact

protected void compact()

Reduces the capacity of and internally reorganizes this SymbolTable, in order to accommodate and access its entries in a more memory efficient way. This method is called automatically when the number of keys in the SymbolTable drops below 25% of this hashtable's load factor (as a result of SoftReferences which have been cleared).

rebalance

protected void rebalance()

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

Overrides:

rebalance in class SymbolTable

containsSymbol

public boolean containsSymbol(java.lang.String symbol)

Returns true if the symbol table already contains the specified symbol.

Overrides:

containsSymbol in class SymbolTable

Parameters:

symbol - The symbol to look for.

containsSymbol

public boolean containsSymbol(char[] buffer,
                     int offset,
                     int length)

Returns true if the symbol table already contains the specified symbol.

Overrides:

containsSymbol in class SymbolTable

Parameters:

buffer - The buffer containing the symbol to look for.

offset - The offset into the buffer.

length - The length of the symbol in the buffer.