Class JapaneseTokenizer
- java.lang.Object
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- org.apache.lucene.util.AttributeSource
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- org.apache.lucene.analysis.TokenStream
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- org.apache.lucene.analysis.Tokenizer
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- org.apache.lucene.analysis.ja.JapaneseTokenizer
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- All Implemented Interfaces:
Closeable
,AutoCloseable
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.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
JapaneseTokenizer.Mode
Tokenization mode: this determines how the tokenizer handles compound and unknown words.-
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
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Field Summary
Fields Modifier and Type Field Description static JapaneseTokenizer.Mode
DEFAULT_MODE
Default tokenization mode.
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Constructor Summary
Constructors Constructor Description JapaneseTokenizer(Reader input, UserDictionary userDictionary, boolean discardPunctuation, JapaneseTokenizer.Mode mode)
Create a new JapaneseTokenizer.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
end()
This method is called by the consumer after the last token has been consumed, afterTokenStream.incrementToken()
returnedfalse
(using the newTokenStream
API).boolean
incrementToken()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.void
reset()
Resets this stream to the beginning.void
reset(Reader input)
Expert: Reset the tokenizer to a new reader.void
setGraphvizFormatter(GraphvizFormatter dotOut)
Expert: set this to produce graphviz (dot) output of the Viterbi lattice-
Methods inherited from class org.apache.lucene.analysis.Tokenizer
close, correctOffset
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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
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Field Detail
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DEFAULT_MODE
public static final JapaneseTokenizer.Mode DEFAULT_MODE
Default tokenization mode. Currently this isJapaneseTokenizer.Mode.SEARCH
.
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Constructor Detail
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JapaneseTokenizer
public JapaneseTokenizer(Reader input, UserDictionary userDictionary, boolean discardPunctuation, JapaneseTokenizer.Mode mode)
Create a new JapaneseTokenizer.- Parameters:
input
- Reader containing textuserDictionary
- Optional: if non-null, user dictionary.discardPunctuation
- true if punctuation tokens should be dropped from the output.mode
- tokenization mode.
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Method Detail
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setGraphvizFormatter
public void setGraphvizFormatter(GraphvizFormatter dotOut)
Expert: set this to produce graphviz (dot) output of the Viterbi lattice
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reset
public void reset(Reader input) throws IOException
Description copied from class:Tokenizer
Expert: Reset the tokenizer to a new reader. Typically, an analyzer (in its reusableTokenStream method) will use this to re-use a previously created tokenizer.- Overrides:
reset
in classTokenizer
- Throws:
IOException
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reset
public void reset() throws IOException
Description copied from class:TokenStream
Resets this stream to the beginning. This is an optional operation, so subclasses may or may not implement this method.TokenStream.reset()
is not needed for the standard indexing process. However, if the tokens of aTokenStream
are intended to be consumed more than once, it is necessary to implementTokenStream.reset()
. Note that if your TokenStream caches tokens and feeds them back again after a reset, it is imperative that you clone the tokens when you store them away (on the first pass) as well as when you return them (on future passes afterTokenStream.reset()
).- Overrides:
reset
in classTokenStream
- Throws:
IOException
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end
public void end()
Description copied from class:TokenStream
This method is called by the consumer after the last token has been consumed, afterTokenStream.incrementToken()
returnedfalse
(using the newTokenStream
API). Streams implementing the old API should upgrade to use this feature. This method can be used to perform any end-of-stream operations, such as setting the final offset of a stream. The final offset of a stream might differ from the offset of the last token eg in case one or more whitespaces followed after the last token, but aWhitespaceTokenizer
was used.- Overrides:
end
in classTokenStream
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incrementToken
public boolean incrementToken() throws IOException
Description copied from class:TokenStream
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriateAttributeImpl
s with the attributes of the next token.The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use
AttributeSource.captureState()
to create a copy of the current attribute state.This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to
AttributeSource.addAttribute(Class)
andAttributeSource.getAttribute(Class)
, references to allAttributeImpl
s that this stream uses should be retrieved during instantiation.To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in
TokenStream.incrementToken()
.- Specified by:
incrementToken
in classTokenStream
- Returns:
- false for end of stream; true otherwise
- Throws:
IOException
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