Class CharTokenizer

An abstract base class for simple, character-oriented tokenizers.

You must specify the required LuceneVersion compatibility when creating CharTokenizer:

A new CharTokenizer API has been introduced with Lucene 3.1. This API moved from UTF-16 code units to UTF-32 codepoints to eventually add support for supplementary characters. The old char based API has been deprecated and should be replaced with the int based methods IsTokenChar(Int32) and Normalize(Int32).

As of Lucene 3.1 each CharTokenizer - constructor expects a LuceneVersion argument. Based on the given LuceneVersion either the new API or a backwards compatibility layer is used at runtime. For LuceneVersion < 3.1 the backwards compatibility layer ensures correct behavior even for indexes build with previous versions of Lucene. If a LuceneVersion >= 3.1 is used CharTokenizer requires the new API to be implemented by the instantiated class. Yet, the old char based API is not required anymore even if backwards compatibility must be preserved. CharTokenizer subclasses implementing the new API are fully backwards compatible if instantiated with LuceneVersion < 3.1.

Note: If you use a subclass of CharTokenizer with LuceneVersion >= 3.1 on an index build with a version < 3.1, created tokens might not be compatible with the terms in your index.

Inheritance
System.Object
AttributeSource
TokenStream
Tokenizer
CharTokenizer
LetterTokenizer
WhitespaceTokenizer
IndicTokenizer
RussianLetterTokenizer
Implements
IDisposable
Inherited Members
Namespace: Lucene.Net.Analysis.Util
Assembly: Lucene.Net.Analysis.Common.dll
Syntax
public abstract class CharTokenizer : Tokenizer, IDisposable

Constructors

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CharTokenizer(LuceneVersion, AttributeSource.AttributeFactory, TextReader)

Creates a new CharTokenizer instance

Declaration
public CharTokenizer(LuceneVersion matchVersion, AttributeSource.AttributeFactory factory, TextReader input)
Parameters
Type Name Description
LuceneVersion matchVersion

Lucene version to match

AttributeSource.AttributeFactory factory

the attribute factory to use for this Tokenizer

TextReader input

the input to split up into tokens

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CharTokenizer(LuceneVersion, TextReader)

Creates a new CharTokenizer instance

Declaration
public CharTokenizer(LuceneVersion matchVersion, TextReader input)
Parameters
Type Name Description
LuceneVersion matchVersion

Lucene version to match

TextReader input

the input to split up into tokens

Methods

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End()

Declaration
public override sealed void End()
Overrides
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IncrementToken()

Declaration
public override sealed bool IncrementToken()
Returns
Type Description
System.Boolean
Overrides
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IsTokenChar(Int32)

Returns true iff a codepoint should be included in a token. This tokenizer generates as tokens adjacent sequences of codepoints which satisfy this predicate. Codepoints for which this is false are used to define token boundaries and are not included in tokens.

Declaration
protected abstract bool IsTokenChar(int c)
Parameters
Type Name Description
System.Int32 c
Returns
Type Description
System.Boolean
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Normalize(Int32)

Called on each token character to normalize it before it is added to the token. The default implementation does nothing. Subclasses may use this to, e.g., lowercase tokens.

Declaration
protected virtual int Normalize(int c)
Parameters
Type Name Description
System.Int32 c
Returns
Type Description
System.Int32
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Reset()

Declaration
public override void Reset()
Overrides

Implements

IDisposable