Class GermanNormalizationFilter

  • All Implemented Interfaces:
    Closeable, AutoCloseable

    public final class GermanNormalizationFilter
    extends org.apache.lucene.analysis.TokenFilter
    Normalizes German characters according to the heuristics of the German2 snowball algorithm. It allows for the fact that ä, ö and ü are sometimes written as ae, oe and ue.

    • 'ß' is replaced by 'ss'
    • 'ä', 'ö', 'ü' are replaced by 'a', 'o', 'u', respectively.
    • 'ae' and 'oe' are replaced by 'a', and 'o', respectively.
    • 'ue' is replaced by 'u', when not following a vowel or q.

    This is useful if you want this normalization without using the German2 stemmer, or perhaps no stemming at all.

    • Nested Class Summary

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

        org.apache.lucene.util.AttributeSource.AttributeFactory, org.apache.lucene.util.AttributeSource.State
    • Field Summary

      • Fields inherited from class org.apache.lucene.analysis.TokenFilter

        input
    • Constructor Summary

      Constructors 
      Constructor Description
      GermanNormalizationFilter​(org.apache.lucene.analysis.TokenStream input)  
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean 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, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString
    • Constructor Detail

      • GermanNormalizationFilter

        public GermanNormalizationFilter​(org.apache.lucene.analysis.TokenStream input)
    • Method Detail

      • incrementToken

        public boolean incrementToken()
                               throws IOException
        Specified by:
        incrementToken in class org.apache.lucene.analysis.TokenStream
        Throws:
        IOException