content: package org.apache.lucene.analysis.miscellaneous;
  
  /**
   * 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 java.io.IOException;
  import java.util.Map;
  
  import org.apache.lucene.analysis.CharArrayMap;
  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.util.Version;
  
  /**
   * Provides the ability to override any {@link KeywordAttribute} aware stemmer
   * with custom dictionary-based stemming.
   */
  public final class StemmerOverrideFilter extends TokenFilter {
    private final CharArrayMap<String> dictionary;
    
    private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
    private final KeywordAttribute keywordAtt = addAttribute(KeywordAttribute.class);
    
    /**
     * Create a new StemmerOverrideFilter, performing dictionary-based stemming
     * with the provided <code>dictionary</code>.
     * <p>
     * Any dictionary-stemmed terms will be marked with {@link KeywordAttribute}
     * so that they will not be stemmed with stemmers down the chain.
     * </p>
     */
    public StemmerOverrideFilter(Version matchVersion, TokenStream input,
        Map<?,String> dictionary) {
      super(input);
      this.dictionary = dictionary instanceof CharArrayMap ? 
          (CharArrayMap<String>) dictionary : CharArrayMap.copy(matchVersion, dictionary);
    }
  
    @Override
    public boolean incrementToken() throws IOException {
      if (input.incrementToken()) {
        if (!keywordAtt.isKeyword()) { // don't muck with already-keyworded terms
          String stem = dictionary.get(termAtt.buffer(), 0, termAtt.length());
          if (stem != null) {
            termAtt.setEmpty().append(stem);
            keywordAtt.setKeyword(true);
          }
        }
        return true;
      } else {
        return false;
      }
    }
  }
  