Class CJKBigramFilter
- 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.TokenFilter
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- org.apache.lucene.analysis.cjk.CJKBigramFilter
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
public final class CJKBigramFilter extends TokenFilter
Forms bigrams of CJK terms that are generated from StandardTokenizer or ICUTokenizer.CJK types are set by these tokenizers, but you can also use
CJKBigramFilter(TokenStream, int)
to explicitly control which of the CJK scripts are turned into bigrams.By default, when a CJK character has no adjacent characters to form a bigram, it is output in unigram form. If you want to always output both unigrams and bigrams, set the
outputUnigrams
flag inCJKBigramFilter(TokenStream, int, boolean)
. This can be used for a combined unigram+bigram approach.In all cases, all non-CJK input is passed thru unmodified.
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Nested Class Summary
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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 java.lang.String
DOUBLE_TYPE
when we emit a bigram, its then marked as this typestatic int
HAN
bigram flag for Han Ideographsstatic int
HANGUL
bigram flag for Hangulstatic int
HIRAGANA
bigram flag for Hiraganastatic int
KATAKANA
bigram flag for Katakanastatic java.lang.String
SINGLE_TYPE
when we emit a unigram, its then marked as this type
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Constructor Summary
Constructors Constructor Description CJKBigramFilter(TokenStream in)
CJKBigramFilter(TokenStream in, int flags)
CJKBigramFilter(TokenStream in, int flags, boolean outputUnigrams)
Create a new CJKBigramFilter, specifying which writing systems should be bigrammed, and whether or not unigrams should also be output.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
incrementToken()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.void
reset()
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
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Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end
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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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HAN
public static final int HAN
bigram flag for Han Ideographs- See Also:
- Constant Field Values
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HIRAGANA
public static final int HIRAGANA
bigram flag for Hiragana- See Also:
- Constant Field Values
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KATAKANA
public static final int KATAKANA
bigram flag for Katakana- See Also:
- Constant Field Values
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HANGUL
public static final int HANGUL
bigram flag for Hangul- See Also:
- Constant Field Values
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DOUBLE_TYPE
public static final java.lang.String DOUBLE_TYPE
when we emit a bigram, its then marked as this type- See Also:
- Constant Field Values
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SINGLE_TYPE
public static final java.lang.String SINGLE_TYPE
when we emit a unigram, its then marked as this type- See Also:
- Constant Field Values
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Constructor Detail
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CJKBigramFilter
public CJKBigramFilter(TokenStream in)
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CJKBigramFilter
public CJKBigramFilter(TokenStream in, int flags)
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CJKBigramFilter
public CJKBigramFilter(TokenStream in, int flags, boolean outputUnigrams)
Create a new CJKBigramFilter, specifying which writing systems should be bigrammed, and whether or not unigrams should also be output.
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Method Detail
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incrementToken
public boolean incrementToken() throws java.io.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:
java.io.IOException
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reset
public void reset() throws java.io.IOException
Description copied from class:TokenFilter
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
.Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.
If you override this method, always call
super.reset()
, otherwise some internal state will not be correctly reset (e.g.,Tokenizer
will throwIllegalStateException
on further usage).NOTE: The default implementation chains the call to the input TokenStream, so be sure to call
super.reset()
when overriding this method.- Overrides:
reset
in classTokenFilter
- Throws:
java.io.IOException
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