Class ICUNormalizer2Filter
- 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.icu.ICUNormalizer2Filter
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- All Implemented Interfaces:
Closeable
,AutoCloseable
- Direct Known Subclasses:
ICUFoldingFilter
public class ICUNormalizer2Filter extends TokenFilter
Normalize token text with ICU'sNormalizer2
With this filter, you can normalize text in the following ways:
- NFKC Normalization, Case Folding, and removing Ignorables (the default)
- Using a standard Normalization mode (NFC, NFD, NFKC, NFKD)
- Based on rules from a custom normalization mapping.
If you use the defaults, this filter is a simple way to standardize Unicode text in a language-independent way for search:
- The case folding that it does can be seen as a replacement for LowerCaseFilter: For example, it handles cases such as the Greek sigma, so that "Μάϊος" and "ΜΆΪΟΣ" will match correctly.
- The normalization will standardizes different forms of the same character in Unicode. For example, CJK full-width numbers will be standardized to their ASCII forms.
- Ignorables such as Zero-Width Joiner and Variation Selectors are removed. These are typically modifier characters that affect display.
- See Also:
Normalizer2
,FilteredNormalizer2
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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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Field Summary
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Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
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Constructor Summary
Constructors Constructor Description ICUNormalizer2Filter(TokenStream input)
Create a new Normalizer2Filter that combines NFKC normalization, Case Folding, and removes Default Ignorables (NFKC_Casefold)ICUNormalizer2Filter(TokenStream input, com.ibm.icu.text.Normalizer2 normalizer)
Create a new Normalizer2Filter with the specified Normalizer2
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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
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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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ICUNormalizer2Filter
public ICUNormalizer2Filter(TokenStream input)
Create a new Normalizer2Filter that combines NFKC normalization, Case Folding, and removes Default Ignorables (NFKC_Casefold)
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ICUNormalizer2Filter
public ICUNormalizer2Filter(TokenStream input, com.ibm.icu.text.Normalizer2 normalizer)
Create a new Normalizer2Filter with the specified Normalizer2- Parameters:
input
- streamnormalizer
- normalizer to use
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Method Detail
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incrementToken
public final boolean incrementToken() throws 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:
IOException
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