Module org.apache.lucene.analysis.common

Package org.apache.lucene.analysis.de

Class GermanAnalyzer

java.lang.Object

org.apache.lucene.analysis.Analyzer

org.apache.lucene.analysis.StopwordAnalyzerBase

org.apache.lucene.analysis.de.GermanAnalyzer

All Implemented Interfaces:

Closeable, AutoCloseable

public final class GermanAnalyzer
extends StopwordAnalyzerBase

Analyzer for German language.

Supports an external list of stopwords (words that will not be indexed at all) and an external list of exclusions (word that will not be stemmed, but indexed). A default set of stopwords is used unless an alternative list is specified, but the exclusion list is empty by default.

NOTE: This class uses the same Version dependent settings as StandardAnalyzer.

NOTE: This class does not decompound nouns, additional data files are needed, incompatible with the Apache 2.0 License. You can find these data files and example code for decompounding here.

Since:

3.1

See Also:

• https://github.com/uschindler/german-decompounder

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	GermanAnalyzer.DefaultSetHolder

Nested classes/interfaces inherited from class org.apache.lucene.analysis.Analyzer

Analyzer.ReuseStrategy, Analyzer.TokenStreamComponents

Field Summary

Fields

Modifier and Type	Field	Description
static final String	DEFAULT_STOPWORD_FILE	File containing default German stopwords.
private final CharArraySet	exclusionSet	Contains words that should be indexed but not stemmed.

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

stopwords

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

GLOBAL_REUSE_STRATEGY, PER_FIELD_REUSE_STRATEGY

Constructor Summary

Constructors

Constructor	Description
GermanAnalyzer()	Builds an analyzer with the default stop words: getDefaultStopSet().
GermanAnalyzer(CharArraySet stopwords)	Builds an analyzer with the given stop words
GermanAnalyzer(CharArraySet stopwords, CharArraySet stemExclusionSet)	Builds an analyzer with the given stop words

Method Summary

Modifier and Type	Method	Description
protected Analyzer.TokenStreamComponents	createComponents(String fieldName)	Creates Analyzer.TokenStreamComponents used to tokenize all the text in the provided Reader.
static final CharArraySet	getDefaultStopSet()	Returns a set of default German-stopwords
protected TokenStream	normalize(String fieldName, TokenStream in)	Wrap the given TokenStream in order to apply normalization filters.

Methods inherited from class org.apache.lucene.analysis.StopwordAnalyzerBase

getStopwordSet, loadStopwordSet, loadStopwordSet, loadStopwordSet

Methods inherited from class org.apache.lucene.analysis.Analyzer

attributeFactory, close, getOffsetGap, getPositionIncrementGap, getReuseStrategy, initReader, initReaderForNormalization, normalize, tokenStream, tokenStream

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DEFAULT_STOPWORD_FILE

public static final String DEFAULT_STOPWORD_FILE

File containing default German stopwords.

See Also:

• Constant Field Values

exclusionSet

private final CharArraySet exclusionSet

Contains words that should be indexed but not stemmed.

Constructor Details

GermanAnalyzer

public GermanAnalyzer()

Builds an analyzer with the default stop words: getDefaultStopSet().

GermanAnalyzer

public GermanAnalyzer(CharArraySet stopwords)

Builds an analyzer with the given stop words

Parameters:

stopwords - a stopword set

GermanAnalyzer

public GermanAnalyzer(CharArraySet stopwords,
 CharArraySet stemExclusionSet)

Builds an analyzer with the given stop words

Parameters:

stopwords - a stopword set

stemExclusionSet - a stemming exclusion set

Method Details

getDefaultStopSet

public static final CharArraySet getDefaultStopSet()

Returns a set of default German-stopwords

Returns:

a set of default German-stopwords

createComponents

protected Analyzer.TokenStreamComponents createComponents(String fieldName)

Creates Analyzer.TokenStreamComponents used to tokenize all the text in the provided Reader.

Specified by:

createComponents in class Analyzer

Parameters:

fieldName - the name of the fields content passed to the Analyzer.TokenStreamComponents sink as a reader

Returns:

Analyzer.TokenStreamComponents built from a StandardTokenizer filtered with LowerCaseFilter, StopFilter, SetKeywordMarkerFilter if a stem exclusion set is provided, GermanNormalizationFilter and GermanLightStemFilter

normalize

protected TokenStream normalize(String fieldName,
 TokenStream in)

Description copied from class: Analyzer

Wrap the given TokenStream in order to apply normalization filters. The default implementation returns the TokenStream as-is. This is used by Analyzer.normalize(String, String).

Overrides:

normalize in class Analyzer