- All Implemented Interfaces:
public final class GermanNormalizationFilter extends TokenFilterNormalizes 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
Constructors Constructor Description
All Methods Instance Methods Concrete Methods Modifier and Type Method Description
IndexWriter) use this method to advance the stream to the next token.
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
public GermanNormalizationFilter(TokenStream input)
public boolean incrementToken() throws java.io.IOExceptionDescription copied from class:
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.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
- Specified by:
- false for end of stream; true otherwise