Class JapaneseKatakanaStemFilter
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Unwrappable<TokenStream>
TokenFilter
that normalizes common katakana spelling variations ending in a long sound
character by removing this character (U+30FC). Only katakana words longer than a minimum length
are stemmed (default is four).
Note that only full-width katakana characters are supported. Please use a CJKWidthFilter
to convert half-width katakana to full-width
before using this filter.
In order to prevent terms from being stemmed, use an instance of SetKeywordMarkerFilter
or a custom TokenFilter
that sets the KeywordAttribute
before this TokenStream
.
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Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final int
private static final char
private final KeywordAttribute
private final int
private final CharTermAttribute
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionboolean
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.private boolean
isKatakana
(char[] term, int length) private int
stem
(char[] term, int length) Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end, reset, unwrap
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState, toString
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Field Details
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DEFAULT_MINIMUM_LENGTH
public static final int DEFAULT_MINIMUM_LENGTH- See Also:
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HIRAGANA_KATAKANA_PROLONGED_SOUND_MARK
private static final char HIRAGANA_KATAKANA_PROLONGED_SOUND_MARK- See Also:
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termAttr
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keywordAttr
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minimumKatakanaLength
private final int minimumKatakanaLength
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Constructor Details
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JapaneseKatakanaStemFilter
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JapaneseKatakanaStemFilter
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Method Details
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incrementToken
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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stem
private int stem(char[] term, int length) -
isKatakana
private boolean isKatakana(char[] term, int length)
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