org.apache.lucene.analysis.cjk
Class CJKBigramFilter

java.lang.Object
  extended by org.apache.lucene.util.AttributeSource
      extended by org.apache.lucene.analysis.TokenStream
          extended by org.apache.lucene.analysis.TokenFilter
              extended by org.apache.lucene.analysis.cjk.CJKBigramFilter
All Implemented Interfaces:
Closeable

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 in CJKBigramFilter(TokenStream, int, boolean). This can be used for a combined unigram+bigram approach.

In all cases, all non-CJK input is passed thru unmodified.


Nested Class Summary
 
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
 
Field Summary
static String DOUBLE_TYPE
          when we emit a bigram, its then marked as this type
static int HAN
          bigram flag for Han Ideographs
static int HANGUL
          bigram flag for Hangul
static int HIRAGANA
          bigram flag for Hiragana
static int KATAKANA
          bigram flag for Katakana
static String SINGLE_TYPE
          when we emit a unigram, its then marked as this type
 
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
 
Constructor Summary
CJKBigramFilter(TokenStream in)
          Calls CJKBigramFilter(in, HAN | HIRAGANA | KATAKANA | HANGUL)
CJKBigramFilter(TokenStream in, int flags)
          Calls CJKBigramFilter(in, flags, false)
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.
 
Method Summary
 boolean incrementToken()
           
 void reset()
           
 
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end
 
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

HAN

public static final int HAN
bigram flag for Han Ideographs

See Also:
Constant Field Values

HIRAGANA

public static final int HIRAGANA
bigram flag for Hiragana

See Also:
Constant Field Values

KATAKANA

public static final int KATAKANA
bigram flag for Katakana

See Also:
Constant Field Values

HANGUL

public static final int HANGUL
bigram flag for Hangul

See Also:
Constant Field Values

DOUBLE_TYPE

public static final String DOUBLE_TYPE
when we emit a bigram, its then marked as this type

See Also:
Constant Field Values

SINGLE_TYPE

public static final String SINGLE_TYPE
when we emit a unigram, its then marked as this type

See Also:
Constant Field Values
Constructor Detail

CJKBigramFilter

public CJKBigramFilter(TokenStream in)
Calls CJKBigramFilter(in, HAN | HIRAGANA | KATAKANA | HANGUL)


CJKBigramFilter

public CJKBigramFilter(TokenStream in,
                       int flags)
Calls CJKBigramFilter(in, flags, false)


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.

Parameters:
flags - OR'ed set from HAN, HIRAGANA, KATAKANA, HANGUL
outputUnigrams - true if unigrams for the selected writing systems should also be output. when this is false, this is only done when there are no adjacent characters to form a bigram.
Method Detail

incrementToken

public boolean incrementToken()
                       throws IOException
Specified by:
incrementToken in class TokenStream
Throws:
IOException

reset

public void reset()
           throws IOException
Overrides:
reset in class TokenFilter
Throws:
IOException


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