All Implemented Interfaces:
Closeable, AutoCloseable, Unwrappable<TokenStream>

public final class CJKWidthFilter extends TokenFilter
A TokenFilter that normalizes CJK width differences:
  • Folds fullwidth ASCII variants into the equivalent basic latin
  • Folds halfwidth Katakana variants into the equivalent kana

NOTE: this filter can be viewed as a (practical) subset of NFKC/NFKD Unicode normalization. See the normalization support in the ICU package for full normalization.

  • Field Details

    • termAtt

      private CharTermAttribute termAtt
    • KANA_NORM

      private static final char[] KANA_NORM
    • KANA_COMBINE_VOICED

      private static final byte[] KANA_COMBINE_VOICED
    • KANA_COMBINE_HALF_VOICED

      private static final byte[] KANA_COMBINE_HALF_VOICED
  • Constructor Details

    • CJKWidthFilter

      public CJKWidthFilter(TokenStream input)
  • Method Details

    • incrementToken

      public 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 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 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) and AttributeSource.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 TokenStream.incrementToken().

      Specified by:
      incrementToken in class TokenStream
      Returns:
      false for end of stream; true otherwise
      Throws:
      IOException
    • combine

      private static boolean combine(char[] text, int pos, char ch)
      returns true if we successfully combined the voice mark