ASCIIFoldingFilter

extends TokenFilter

java.lang.Object
↳	org.apache.lucene.util.AttributeSource
	↳	org.apache.lucene.analysis.TokenStream
		↳	org.apache.lucene.analysis.TokenFilter
			↳	org.apache.lucene.analysis.ASCIIFoldingFilter

Class Overview

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

See: http://en.wikipedia.org/wiki/Latin_characters_in_Unicode The set of character conversions supported by this class is a superset of those supported by Lucene's ISOLatin1AccentFilter which strips accents from Latin1 characters. For example, 'à' will be replaced by 'a'.

Summary

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Inherited Fields

From class org.apache.lucene.analysis.TokenFilter

Public Constructors
	ASCIIFoldingFilter(TokenStream input)

Public Methods
void	foldToASCII(char[] input, 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.

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Inherited Methods

From class org.apache.lucene.analysis.TokenFilter

From class org.apache.lucene.analysis.TokenStream

From class org.apache.lucene.util.AttributeSource

From class java.lang.Object

From interface java.io.Closeable

Public Constructors

public ASCIIFoldingFilter (TokenStream input)

Public Methods

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 fold
length	The number of characters in the input string

public boolean incrementToken ()

Consumers (i.e., IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate AttributeImpls 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 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 addAttribute(Class) and getAttribute(Class), references to all AttributeImpls 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 incrementToken().

Returns

false for end of stream; true otherwise

Throws

IOException

Classes