org.apache.lucene.analysis.util
Class CharTokenizer

java.lang.Object
  extended by org.apache.lucene.util.AttributeSource
      extended by org.apache.lucene.analysis.TokenStream
          extended by org.apache.lucene.analysis.Tokenizer
              extended by 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:

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, AttributeSource source, 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
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

CharTokenizer

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

Parameters:
matchVersion - Lucene version to match See above
input - the input to split up into tokens

CharTokenizer

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

Parameters:
matchVersion - Lucene version to match See above
source - the attribute source to use for this Tokenizer
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 See above
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()
Overrides:
end in class TokenStream

reset

public void reset()
           throws IOException
Overrides:
reset in class TokenStream
Throws:
IOException


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