content: package org.apache.lucene.analysis.ru;
  
  /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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.KeywordMarkerFilter;// for javadoc
  import org.apache.lucene.analysis.LowerCaseFilter; // for javadoc
  import org.apache.lucene.analysis.TokenFilter;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.tokenattributes.KeywordAttribute;
  import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
  import org.apache.lucene.analysis.ru.RussianStemmer;//javadoc @link
  import org.apache.lucene.analysis.snowball.SnowballFilter; // javadoc @link
  
  import java.io.IOException;
  
  /**
   * A {@link TokenFilter} that stems Russian words. 
   * <p>
   * The implementation was inspired by GermanStemFilter.
   * The input should be filtered by {@link LowerCaseFilter} before passing it to RussianStemFilter ,
   * because RussianStemFilter only works with lowercase characters.
   * </p>
   * <p>
   * To prevent terms from being stemmed use an instance of
   * {@link KeywordMarkerFilter} or a custom {@link TokenFilter} that sets
   * the {@link KeywordAttribute} before this {@link TokenStream}.
   * </p>
   * @see KeywordMarkerFilter
   * @deprecated Use {@link SnowballFilter} with 
   * {@link org.tartarus.snowball.ext.RussianStemmer} instead, which has the
   * same functionality. This filter will be removed in Lucene 4.0
   */
  @Deprecated
  public final class RussianStemFilter extends TokenFilter
  {
      /**
       * The actual token in the input stream.
       */
      private RussianStemmer stemmer = new RussianStemmer();
  
      private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
      private final KeywordAttribute keywordAttr = addAttribute(KeywordAttribute.class);
  
      public RussianStemFilter(TokenStream in)
      {
          super(in);
      }
      /**
       * Returns the next token in the stream, or null at EOS
       */
      @Override
      public final boolean incrementToken() throws IOException
      {
        if (input.incrementToken()) {
          if(!keywordAttr.isKeyword()) {
            final String term = termAtt.toString();
            final String s = stemmer.stem(term);
            if (s != null && !s.equals(term))
              termAtt.setEmpty().append(s);
          }
          return true;
        } else {
          return false;
        }
      }
  
  
      /**
       * Set a alternative/custom {@link RussianStemmer} for this filter.
       */
      public void setStemmer(RussianStemmer stemmer)
      {
          if (stemmer != null)
          {
              this.stemmer = stemmer;
          }
      }
  }
  