org.apache.lucene.analysis.de
Class GermanNormalizationFilter

java.lang.Object
  org.apache.lucene.util.AttributeSource
      org.apache.lucene.analysis.TokenStream
          org.apache.lucene.analysis.TokenFilter
              org.apache.lucene.analysis.de.GermanNormalizationFilter

All Implemented Interfaces:

Closeable

public final class GermanNormalizationFilter
extends 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

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

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

input

Constructor Summary

GermanNormalizationFilter(TokenStream input)

Method Summary

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

Methods inherited from class java.lang.Object

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

Constructor Detail

GermanNormalizationFilter

public GermanNormalizationFilter(TokenStream input)

Method Detail

incrementToken

public boolean incrementToken()
                       throws IOException

Specified by:

incrementToken in class TokenStream

Throws:

IOException