package org.apache.lucene.analysis.fr;
/**
* Copyright 2004-2005 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import org.apache.lucene.analysis.Token;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import java.io.IOException;
import java.util.Hashtable;
import java.util.HashSet;
import java.util.Set;
/**
* A filter that stemms french words. It supports a table of words that should
* not be stemmed at all. The used stemmer can be changed at runtime after the
* filter object is created (as long as it is a FrenchStemmer).
*
* @author Patrick Talbot (based on Gerhard Schwarz work for German)
*/
public final class FrenchStemFilter extends TokenFilter {
/**
* The actual token in the input stream.
*/
private Token token = null;
private FrenchStemmer stemmer = null;
private Set exclusions = null;
public FrenchStemFilter( TokenStream in ) {
super(in);
stemmer = new FrenchStemmer();
}
/**
* Builds a FrenchStemFilter that uses an exclusiontable.
*
* @deprecated
*/
public FrenchStemFilter( TokenStream in, Hashtable exclusiontable ) {
this( in );
exclusions = new HashSet(exclusiontable.keySet());
}
public FrenchStemFilter( TokenStream in, Set exclusiontable ) {
this( in );
exclusions = exclusiontable;
}
/**
* @return Returns the next token in the stream, or null at EOS
*/
public final Token next()
throws IOException {
if ( ( token = input.next() ) == null ) {
return null;
}
// Check the exclusiontable
else if ( exclusions != null && exclusions.contains( token.termText() ) ) {
return token;
}
else {
String s = stemmer.stem( token.termText() );
// If not stemmed, dont waste the time creating a new token
if ( !s.equals( token.termText() ) ) {
return new Token( s, token.startOffset(), token.endOffset(), token.type());
}
return token;
}
}
/**
* Set a alternative/custom FrenchStemmer for this filter.
*/
public void setStemmer( FrenchStemmer stemmer ) {
if ( stemmer != null ) {
this.stemmer = stemmer;
}
}
/**
* Set an alternative exclusion list for this filter.
*/
public void setExclusionTable( Hashtable exclusiontable ) {
exclusions = new HashSet(exclusiontable.keySet());
}
}
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