org.apache.lucene.analysis.icu

## Class ICUFoldingFilter

- java.lang.Object
- - org.apache.lucene.util.AttributeSource
  - - org.apache.lucene.analysis.TokenStream
    - - org.apache.lucene.analysis.TokenFilter
      - - org.apache.lucene.analysis.icu.ICUNormalizer2Filter
        - - org.apache.lucene.analysis.icu.ICUFoldingFilter

- All Implemented Interfaces:
    Closeable, AutoCloseable

      public final class ICUFoldingFilter
      extends ICUNormalizer2Filter

  A TokenFilter that applies search term folding to Unicode text, applying foldings from UTR#30 Character Foldings.

  This filter applies the following foldings from the report to unicode text:

  - Accent removal
  - Case folding
  - Canonical duplicates folding
  - Dashes folding
  - Diacritic removal (including stroke, hook, descender)
  - Greek letterforms folding
  - Han Radical folding
  - Hebrew Alternates folding
  - Jamo folding
  - Letterforms folding
  - Math symbol folding
  - Multigraph Expansions: All
  - Native digit folding
  - No-break folding
  - Overline folding
  - Positional forms folding
  - Small forms folding
  - Space folding
  - Spacing Accents folding
  - Subscript folding
  - Superscript folding
  - Suzhou Numeral folding
  - Symbol folding
  - Underline folding
  - Vertical forms folding
  - Width folding

  Additionally, Default Ignorables are removed, and text is normalized to NFKC. All foldings, case folding, and normalization mappings are applied recursively to ensure a fully folded and normalized result.

  A normalizer with additional settings such as a filter that lists characters not to be normalized can be passed in the constructor.

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

      `AttributeSource.State`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static com.ibm.icu.text.Normalizer2` | `NORMALIZER` A normalizer for search term folding to Unicode text, applying foldings from UTR#30 Character Foldings.

    - ### Fields inherited from class org.apache.lucene.analysis.TokenFilter

      `input`

    - ### Fields inherited from class org.apache.lucene.analysis.TokenStream

      `DEFAULT_TOKEN_ATTRIBUTE_FACTORY`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ICUFoldingFilter(TokenStream input)` Create a new ICUFoldingFilter on the specified input
    `ICUFoldingFilter(TokenStream input, com.ibm.icu.text.Normalizer2 normalizer)` Create a new ICUFoldingFilter on the specified input with the specified normalizer

  - ### Method Summary

    - ### Methods inherited from class org.apache.lucene.analysis.icu.ICUNormalizer2Filter

      `incrementToken`

    - ### Methods inherited from class org.apache.lucene.analysis.TokenFilter

      `close, end, reset`

    - ### 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`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### NORMALIZER

          public static final com.ibm.icu.text.Normalizer2 NORMALIZER

      A normalizer for search term folding to Unicode text, applying foldings from UTR#30 Character Foldings.

  - ### Constructor Detail

    - #### ICUFoldingFilter

          public ICUFoldingFilter(TokenStream input)

      Create a new ICUFoldingFilter on the specified input

    - #### ICUFoldingFilter

          public ICUFoldingFilter(TokenStream input,
                                  com.ibm.icu.text.Normalizer2 normalizer)

      Create a new ICUFoldingFilter on the specified input with the specified normalizer

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