Class ASCIIFoldingFilter
- 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.ASCIIFoldingFilter
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
public final class ASCIIFoldingFilter extends TokenFilter
This class converts alphabetic, numeric, and symbolic Unicode characters which are not in the first 127 ASCII characters (the "Basic Latin" Unicode block) into their ASCII equivalents, if one exists. Characters from the following Unicode blocks are converted; however, only those characters with reasonable ASCII alternatives are converted:- C1 Controls and Latin-1 Supplement: http://www.unicode.org/charts/PDF/U0080.pdf
- Latin Extended-A: http://www.unicode.org/charts/PDF/U0100.pdf
- Latin Extended-B: http://www.unicode.org/charts/PDF/U0180.pdf
- Latin Extended Additional: http://www.unicode.org/charts/PDF/U1E00.pdf
- Latin Extended-C: http://www.unicode.org/charts/PDF/U2C60.pdf
- Latin Extended-D: http://www.unicode.org/charts/PDF/UA720.pdf
- IPA Extensions: http://www.unicode.org/charts/PDF/U0250.pdf
- Phonetic Extensions: http://www.unicode.org/charts/PDF/U1D00.pdf
- Phonetic Extensions Supplement: http://www.unicode.org/charts/PDF/U1D80.pdf
- General Punctuation: http://www.unicode.org/charts/PDF/U2000.pdf
- Superscripts and Subscripts: http://www.unicode.org/charts/PDF/U2070.pdf
- Enclosed Alphanumerics: http://www.unicode.org/charts/PDF/U2460.pdf
- Dingbats: http://www.unicode.org/charts/PDF/U2700.pdf
- Supplemental Punctuation: http://www.unicode.org/charts/PDF/U2E00.pdf
- Alphabetic Presentation Forms: http://www.unicode.org/charts/PDF/UFB00.pdf
- Halfwidth and Fullwidth Forms: http://www.unicode.org/charts/PDF/UFF00.pdf
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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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Constructor Summary
Constructors Constructor Description ASCIIFoldingFilter(TokenStream input)
ASCIIFoldingFilter(TokenStream input, boolean preserveOriginal)
Create a newASCIIFoldingFilter
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
foldToASCII(char[] input, int length)
Converts characters above ASCII to their ASCII equivalents.static int
foldToASCII(char[] input, int inputPos, char[] output, int outputPos, int length)
Converts characters above ASCII to their ASCII equivalents.boolean
incrementToken()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.boolean
isPreserveOriginal()
Does the filter preserve the original tokens?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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Constructor Detail
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ASCIIFoldingFilter
public ASCIIFoldingFilter(TokenStream input)
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ASCIIFoldingFilter
public ASCIIFoldingFilter(TokenStream input, boolean preserveOriginal)
Create a newASCIIFoldingFilter
.- Parameters:
input
- TokenStream to filterpreserveOriginal
- should the original tokens be kept on the input stream with a 0 position increment from the folded tokens?
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Method Detail
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isPreserveOriginal
public boolean isPreserveOriginal()
Does the filter preserve the original tokens?
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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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foldToASCII
public void foldToASCII(char[] input, int length)
Converts characters above ASCII to their ASCII equivalents. For example, accents are removed from accented characters.- Parameters:
input
- The string to foldlength
- The number of characters in the input string
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foldToASCII
public static final int foldToASCII(char[] input, int inputPos, char[] output, int outputPos, int length)
Converts characters above ASCII to their ASCII equivalents. For example, accents are removed from accented characters.- Parameters:
input
- The characters to foldinputPos
- Index of the first character to foldoutput
- The result of the folding. Should be of size >=length * 4
.outputPos
- Index of output where to put the result of the foldinglength
- The number of characters to fold- Returns:
- length of output
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