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.Unlike ICUTokenizer, StandardTokenizer does not split at script boundaries. Korean Hangul characters are treated the same as many other scripts' letters, and as a result, StandardTokenizer can produce tokens that mix Hangul and non-Hangul characters, e.g. "한국abc". Such mixed-script tokens are typed as
<ALPHANUM>
rather than<HANGUL>
, and as a result, will not be converted to bigrams by CJKBigramFilter. 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.State
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Field Summary
Fields Modifier and Type Field Description (package private) int[]
buffer
(package private) int
bufferLen
private java.lang.Object
doHan
private java.lang.Object
doHangul
private java.lang.Object
doHiragana
private java.lang.Object
doKatakana
static java.lang.String
DOUBLE_TYPE
when we emit a bigram, it's then marked as this type(package private) int[]
endOffset
private boolean
exhausted
static int
HAN
bigram flag for Han Ideographsprivate static java.lang.String
HAN_TYPE
static int
HANGUL
bigram flag for Hangulprivate static java.lang.String
HANGUL_TYPE
static int
HIRAGANA
bigram flag for Hiraganaprivate static java.lang.String
HIRAGANA_TYPE
(package private) int
index
static int
KATAKANA
bigram flag for Katakanaprivate static java.lang.String
KATAKANA_TYPE
(package private) int
lastEndOffset
private AttributeSource.State
loneState
private boolean
ngramState
private static java.lang.Object
NO
private OffsetAttribute
offsetAtt
private boolean
outputUnigrams
private PositionIncrementAttribute
posIncAtt
private PositionLengthAttribute
posLengthAtt
static java.lang.String
SINGLE_TYPE
when we emit a unigram, it's then marked as this type(package private) int[]
startOffset
private CharTermAttribute
termAtt
private TypeAttribute
typeAtt
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Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
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Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
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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 private boolean
doNext()
looks at next input token, returning false is none is availableprivate void
flushBigram()
Flushes a bigram token to output from our buffer This is the normal case, e.g.private void
flushUnigram()
Flushes a unigram token to output from our buffer.private boolean
hasBufferedBigram()
True if we have multiple codepoints sitting in our bufferprivate boolean
hasBufferedUnigram()
True if we have a single codepoint sitting in our buffer, where its future (whether it is emitted as unigram or forms a bigram) depends upon not-yet-seen inputs.boolean
incrementToken()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.private void
refill()
refills buffers with new data from the current 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, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, 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, it's 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, it's then marked as this type- See Also:
- Constant Field Values
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HAN_TYPE
private static final java.lang.String HAN_TYPE
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HIRAGANA_TYPE
private static final java.lang.String HIRAGANA_TYPE
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KATAKANA_TYPE
private static final java.lang.String KATAKANA_TYPE
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HANGUL_TYPE
private static final java.lang.String HANGUL_TYPE
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NO
private static final java.lang.Object NO
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doHan
private final java.lang.Object doHan
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doHiragana
private final java.lang.Object doHiragana
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doKatakana
private final java.lang.Object doKatakana
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doHangul
private final java.lang.Object doHangul
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outputUnigrams
private final boolean outputUnigrams
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ngramState
private boolean ngramState
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termAtt
private final CharTermAttribute termAtt
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typeAtt
private final TypeAttribute typeAtt
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offsetAtt
private final OffsetAttribute offsetAtt
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posIncAtt
private final PositionIncrementAttribute posIncAtt
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posLengthAtt
private final PositionLengthAttribute posLengthAtt
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buffer
int[] buffer
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startOffset
int[] startOffset
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endOffset
int[] endOffset
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bufferLen
int bufferLen
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index
int index
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lastEndOffset
int lastEndOffset
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exhausted
private boolean exhausted
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loneState
private AttributeSource.State loneState
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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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doNext
private boolean doNext() throws java.io.IOException
looks at next input token, returning false is none is available- Throws:
java.io.IOException
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refill
private void refill()
refills buffers with new data from the current token.
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flushBigram
private void flushBigram()
Flushes a bigram token to output from our buffer This is the normal case, e.g. ABC -> AB BC
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flushUnigram
private void flushUnigram()
Flushes a unigram token to output from our buffer. This happens when we encounter isolated CJK characters, either the whole CJK string is a single character, or we encounter a CJK character surrounded by space, punctuation, english, etc, but not beside any other CJK.
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hasBufferedBigram
private boolean hasBufferedBigram()
True if we have multiple codepoints sitting in our buffer
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hasBufferedUnigram
private boolean hasBufferedUnigram()
True if we have a single codepoint sitting in our buffer, where its future (whether it is emitted as unigram or forms a bigram) depends upon not-yet-seen inputs.
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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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