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.
Method Summary |
boolean |
incrementToken()
Consumers (i.e., IndexWriter ) use this method to advance the stream to
the next token. |
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 |
GermanNormalizationFilter
public GermanNormalizationFilter(TokenStream input)
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 AttributeImpl
s 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 AttributeImpl
s 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