Class ScandinavianFoldingFilter
- 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.miscellaneous.ScandinavianFoldingFilter
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
,Unwrappable<TokenStream>
public final class ScandinavianFoldingFilter extends TokenFilter
This filter folds Scandinavian characters åÅäæÄÆ->a and öÖøØ->o. It also discriminate against use of double vowels aa, ae, ao, oe and oo, leaving just the first one.It's a semantically more destructive solution than
ScandinavianNormalizationFilter
but can in addition help with matching raksmorgas as räksmörgås.blåbærsyltetøj == blåbärsyltetöj == blaabaarsyltetoej == blabarsyltetoj räksmörgås == ræksmørgås == ræksmörgaos == raeksmoergaas == raksmorgas
Background: Swedish åäö are in fact the same letters as Norwegian and Danish åæø and thus interchangeable when used between these languages. They are however folded differently when people type them on a keyboard lacking these characters.
In that situation almost all Swedish people use a, a, o instead of å, ä, ö.
Norwegians and Danes on the other hand usually type aa, ae and oe instead of å, æ and ø. Some do however use a, a, o, oo, ao and sometimes permutations of everything above.
This filter solves that mismatch problem, but might also cause new.
- See Also:
ScandinavianNormalizationFilter
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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 private static char
aa
private static char
AA
private static char
ae
private static char
AE
private static char
ae_se
private static char
AE_se
private CharTermAttribute
charTermAttribute
private static char
oe
private static char
OE
private static char
oe_se
private static char
OE_se
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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 ScandinavianFoldingFilter(TokenStream input)
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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.-
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end, reset, unwrap
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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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charTermAttribute
private final CharTermAttribute charTermAttribute
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AA
private static final char AA
- See Also:
- Constant Field Values
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aa
private static final char aa
- See Also:
- Constant Field Values
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AE
private static final char AE
- See Also:
- Constant Field Values
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ae
private static final char ae
- See Also:
- Constant Field Values
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AE_se
private static final char AE_se
- See Also:
- Constant Field Values
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ae_se
private static final char ae_se
- See Also:
- Constant Field Values
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OE
private static final char OE
- See Also:
- Constant Field Values
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oe
private static final char oe
- See Also:
- Constant Field Values
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OE_se
private static final char OE_se
- See Also:
- Constant Field Values
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oe_se
private static final char oe_se
- See Also:
- Constant Field Values
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Constructor Detail
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ScandinavianFoldingFilter
public ScandinavianFoldingFilter(TokenStream input)
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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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