com.devexperts.util

Class StringCache

java.lang.Object

com.devexperts.util.StringCache

public class StringCache
extends Object

Caches strings and provides lookup methods by raw character data to avoid string construction. It is intended to be used in various parsers to reduce memory footprint and garbage.

The StringCache is a N-way set associative cache which distributes all strings into buckets based on hash function and then uses LRU algorithm within each bucket. The StringCache is a thread-safe, asynchronous, wait-free data structure.

Constructor Summary

Constructors

Constructor and Description
StringCache() Creates a StringCache with default parameters.
StringCache(int size) Creates a StringCache with the specified number of elements and default bucket size.
StringCache(int bucketNumber, int bucketSize) Creates a StringCache with the specified number of buckets and their size.

Method Summary

Modifier and Type	Method and Description
String	get(char[] c) Returns string from the cache that matches specified character sequence.
String	get(char[] c, int offset, int length) Returns string from the cache that matches specified character sequence.
String	get(CharSequence cs) Returns string from the cache that matches specified character sequence.
String	get(CharSequence cs, int offset, int length) Returns string from the cache that matches specified character sequence.
String	get(String s) Returns string from the cache that matches specified string.
String	get(String s, boolean copy) Returns string from the cache that matches specified string.
String	get(String s, int offset, int length) Returns string from the cache that matches specified character sequence.
String	getASCII(byte[] b) Returns string from the cache that matches specified character sequence.
String	getASCII(byte[] b, int offset, int length) Returns string from the cache that matches specified character sequence.
String	getShortString(long code) Returns string from the cache that matches specified character sequence.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

StringCache

public StringCache()

Creates a StringCache with default parameters.

StringCache

public StringCache(int size)

Creates a StringCache with the specified number of elements and default bucket size.

Parameters:

size - the number of elements

Throws:

IllegalArgumentException - if size is not positive or result in too large cache

StringCache

public StringCache(int bucketNumber,
                   int bucketSize)

Creates a StringCache with the specified number of buckets and their size.

NOTE: cache uses linear search within each bucket, so do not use very large bucket sizes.

Parameters:

bucketNumber - the number of buckets

bucketSize - the size of each bucket

Throws:

IllegalArgumentException - if parameters are not positive or result in too large cache

Method Detail

get

public String get(String s)

Returns string from the cache that matches specified string.

get

public String get(String s,
                  boolean copy)

Returns string from the cache that matches specified string. If copy parameter is true then specified string will be copied before being put to cache.

get

public String get(String s,
                  int offset,
                  int length)

Returns string from the cache that matches specified character sequence.

get

public String get(CharSequence cs)

Returns string from the cache that matches specified character sequence.

get

public String get(CharSequence cs,
                  int offset,
                  int length)

Returns string from the cache that matches specified character sequence.

get

public String get(char[] c)

Returns string from the cache that matches specified character sequence.

get

public String get(char[] c,
                  int offset,
                  int length)

Returns string from the cache that matches specified character sequence.

getASCII

public String getASCII(byte[] b)

Returns string from the cache that matches specified character sequence. This method uses only 7 lowest bits (ASCII range) of each character ignoring higher bits.

getASCII

public String getASCII(byte[] b,
                       int offset,
                       int length)

Returns string from the cache that matches specified character sequence. This method uses only 7 lowest bits (ASCII range) of each character ignoring higher bits.

getShortString

public String getShortString(long code)

Returns string from the cache that matches specified character sequence. This method uses string encoding technique defined in ShortString class.

toString

public String toString()

Overrides:

toString in class Object