org.apache.lucene.analysis.ja

Class JapaneseTokenizer

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.Tokenizer

org.apache.lucene.analysis.ja.JapaneseTokenizer

All Implemented Interfaces:

Closeable

public final class JapaneseTokenizer
extends Tokenizer

Tokenizer for Japanese that uses morphological analysis.

This tokenizer sets a number of additional attributes:

• BaseFormAttribute containing base form for inflected adjectives and verbs.
• PartOfSpeechAttribute containing part-of-speech.
• ReadingAttribute containing reading and pronunciation.
• InflectionAttribute containing additional part-of-speech information for inflected forms.

This tokenizer uses a rolling Viterbi search to find the least cost segmentation (path) of the incoming characters. For tokens that appear to be compound (> length 2 for all Kanji, or > length 7 for non-Kanji), we see if there is a 2nd best segmentation of that token after applying penalties to the long tokens. If so, and the Mode is JapaneseTokenizer.Mode.SEARCH, we output the alternate segmentation as well.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	JapaneseTokenizer.Mode Tokenization mode: this determines how the tokenizer handles compound and unknown words.
static class	JapaneseTokenizer.Type Token type reflecting the original source of this token

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

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

Fields

Modifier and Type	Field and Description
static JapaneseTokenizer.Mode	DEFAULT_MODE Default tokenization mode.

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

input

Constructor Summary

Constructors

Constructor and Description
JapaneseTokenizer(Reader input, UserDictionary userDictionary, boolean discardPunctuation, JapaneseTokenizer.Mode mode) Create a new JapaneseTokenizer.

Method Summary

Methods

Modifier and Type	Method and Description
void	end()
boolean	incrementToken()
void	reset()
void	setGraphvizFormatter(GraphvizFormatter dotOut) Expert: set this to produce graphviz (dot) output of the Viterbi lattice
void	setReader(Reader input)

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

close, correctOffset

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

Field Detail

DEFAULT_MODE

public static final JapaneseTokenizer.Mode DEFAULT_MODE

Default tokenization mode. Currently this is JapaneseTokenizer.Mode.SEARCH.

Constructor Detail

JapaneseTokenizer

public JapaneseTokenizer(Reader input,
                 UserDictionary userDictionary,
                 boolean discardPunctuation,
                 JapaneseTokenizer.Mode mode)

Create a new JapaneseTokenizer.

Parameters:

input - Reader containing text

userDictionary - Optional: if non-null, user dictionary.

discardPunctuation - true if punctuation tokens should be dropped from the output.

mode - tokenization mode.

Method Detail

setGraphvizFormatter

public void setGraphvizFormatter(GraphvizFormatter dotOut)

Expert: set this to produce graphviz (dot) output of the Viterbi lattice

setReader

public void setReader(Reader input)
               throws IOException

Overrides:

setReader in class Tokenizer

Throws:

IOException

reset

public void reset()
           throws IOException

Overrides:

reset in class TokenStream

Throws:

IOException

end

public void end()

Overrides:

end in class TokenStream

incrementToken

public boolean incrementToken()
                       throws IOException

Specified by:

incrementToken in class TokenStream

Throws:

IOException