org.apache.lucene.analysis.util
Class CharTokenizer

java.lang.Object
  org.apache.lucene.util.AttributeSource
      org.apache.lucene.analysis.TokenStream
          org.apache.lucene.analysis.Tokenizer
              org.apache.lucene.analysis.util.CharTokenizer

All Implemented Interfaces:

Closeable

Direct Known Subclasses:

IndicTokenizer, LetterTokenizer, RussianLetterTokenizer, WhitespaceTokenizer

public abstract class CharTokenizer
extends Tokenizer

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

You must specify the required Version compatibility when creating CharTokenizer:

• As of 3.1, CharTokenizer uses an int based API to normalize and detect token codepoints. See isTokenChar(int) and normalize(int) for details.

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(int) and normalize(int).

As of Lucene 3.1 each CharTokenizer - constructor expects a Version argument. Based on the given Version either the new API or a backwards compatibility layer is used at runtime. For Version < 3.1 the backwards compatibility layer ensures correct behavior even for indexes build with previous versions of Lucene. If a Version >= 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 Version < 3.1.

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

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

Fields inherited from class org.apache.lucene.analysis.Tokenizer

input

Constructor Summary

CharTokenizer(Version matchVersion, AttributeSource.AttributeFactory factory, Reader input)
Creates a new CharTokenizer instance

CharTokenizer(Version matchVersion, Reader input)
Creates a new CharTokenizer instance

Method Summary

void	end()
boolean	incrementToken()
protected abstract boolean	isTokenChar(int c) Returns true iff a codepoint should be included in a token.
protected int	normalize(int c) Called on each token character to normalize it before it is added to the token.
void	reset()

Methods inherited from class org.apache.lucene.analysis.Tokenizer

close, correctOffset, setReader

Methods inherited from class org.apache.lucene.util.AttributeSource

addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

CharTokenizer

public CharTokenizer(Version matchVersion,
                     Reader input)

Creates a new CharTokenizer instance

Parameters:

matchVersion - Lucene version to match

input - the input to split up into tokens

CharTokenizer

public CharTokenizer(Version matchVersion,
                     AttributeSource.AttributeFactory factory,
                     Reader input)

Creates a new CharTokenizer instance

Parameters:

matchVersion - Lucene version to match

factory - the attribute factory to use for this Tokenizer

input - the input to split up into tokens

Method Detail

isTokenChar

protected abstract boolean isTokenChar(int c)

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.

normalize

protected int normalize(int c)

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.

incrementToken

public final boolean incrementToken()
                             throws IOException

Specified by:

incrementToken in class TokenStream

Throws:

IOException

end

public final void end()
               throws IOException

Overrides:

end in class TokenStream

Throws:

IOException

reset

public void reset()
           throws IOException

Overrides:

reset in class Tokenizer

Throws:

IOException