content: package org.apache.lucene.analysis.de;
  // This file is encoded in UTF-8
  
  /**
   * 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.File;
  import java.io.IOException;
  import java.io.Reader;
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  
  import org.apache.lucene.analysis.Analyzer;
  import org.apache.lucene.analysis.CharArraySet;
  import org.apache.lucene.analysis.LowerCaseFilter;
  import org.apache.lucene.analysis.KeywordMarkerFilter;
  import org.apache.lucene.analysis.StopFilter;
  import org.apache.lucene.analysis.StopwordAnalyzerBase;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.Tokenizer;
  import org.apache.lucene.analysis.WordlistLoader;
  import org.apache.lucene.analysis.snowball.SnowballFilter;
  import org.apache.lucene.analysis.standard.StandardAnalyzer;
  import org.apache.lucene.analysis.standard.StandardFilter;
  import org.apache.lucene.analysis.standard.StandardTokenizer;
  import org.apache.lucene.util.IOUtils;
  import org.apache.lucene.util.Version;
  import org.tartarus.snowball.ext.German2Stemmer;
  
  /**
   * {@link Analyzer} for German language. 
   * <p>
   * 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.
   * </p>
   * 
   * <a name="version"/>
   * <p>You must specify the required {@link Version}
   * compatibility when creating GermanAnalyzer:
   * <ul>
   *   <li> As of 3.1, Snowball stemming is done with SnowballFilter, and 
   *        Snowball stopwords are used by default.
   *   <li> As of 2.9, StopFilter preserves position
   *        increments
   * </ul>
   * 
   * <p><b>NOTE</b>: This class uses the same {@link Version}
   * dependent settings as {@link StandardAnalyzer}.</p>
   */
  public final class GermanAnalyzer extends StopwordAnalyzerBase {
    
    /**
     * List of typical german stopwords.
     * @deprecated use {@link #getDefaultStopSet()} instead
     */
    @Deprecated
    public final static String[] GERMAN_STOP_WORDS = {
      "einer", "eine", "eines", "einem", "einen",
      "der", "die", "das", "dass", "daß",
      "du", "er", "sie", "es",
      "was", "wer", "wie", "wir",
      "und", "oder", "ohne", "mit",
      "am", "im", "in", "aus", "auf",
      "ist", "sein", "war", "wird",
      "ihr", "ihre", "ihres",
      "als", "für", "von", "mit",
      "dich", "dir", "mich", "mir",
      "mein", "sein", "kein",
      "durch", "wegen", "wird"
    };
    
    /** File containing default German stopwords. */
    public final static String DEFAULT_STOPWORD_FILE = "german_stop.txt";
    
    /**
     * Returns a set of default German-stopwords 
     * @return a set of default German-stopwords 
     */
    public static final Set<?> getDefaultStopSet(){
      return DefaultSetHolder.DEFAULT_SET;
    }
    
    private static class DefaultSetHolder {
      /** @deprecated remove in Lucene 5.0 */
      @Deprecated
      private static final Set<?> DEFAULT_SET_30 = CharArraySet.unmodifiableSet(new CharArraySet(
          Version.LUCENE_CURRENT, Arrays.asList(GERMAN_STOP_WORDS), false));
      private static final Set<?> DEFAULT_SET;
      static {
        try {
          DEFAULT_SET = WordlistLoader.getSnowballWordSet(IOUtils.getDecodingReader(SnowballFilter.class, 
              DEFAULT_STOPWORD_FILE, IOUtils.CHARSET_UTF_8), Version.LUCENE_CURRENT);
        } catch (IOException ex) {
          // default set should always be present as it is part of the
          // distribution (JAR)
          throw new RuntimeException("Unable to load default stopword set");
        }
      }
    }
  
    /**
     * Contains the stopwords used with the {@link StopFilter}.
     */
   
    /**
     * Contains words that should be indexed but not stemmed.
     */
    // TODO make this final in 3.1
    private Set<?> exclusionSet;
  
    /**
     * Builds an analyzer with the default stop words:
     * {@link #getDefaultStopSet()}.
     */
    public GermanAnalyzer(Version matchVersion) {
      this(matchVersion,
          matchVersion.onOrAfter(Version.LUCENE_31) ? DefaultSetHolder.DEFAULT_SET
              : DefaultSetHolder.DEFAULT_SET_30);
    }
    
    /**
     * Builds an analyzer with the given stop words 
     * 
     * @param matchVersion
     *          lucene compatibility version
     * @param stopwords
     *          a stopword set
     */
    public GermanAnalyzer(Version matchVersion, Set<?> stopwords) {
      this(matchVersion, stopwords, CharArraySet.EMPTY_SET);
    }
    
    /**
     * Builds an analyzer with the given stop words
     * 
     * @param matchVersion
     *          lucene compatibility version
     * @param stopwords
     *          a stopword set
     * @param stemExclusionSet
     *          a stemming exclusion set
     */
    public GermanAnalyzer(Version matchVersion, Set<?> stopwords, Set<?> stemExclusionSet) {
      super(matchVersion, stopwords);
      exclusionSet = CharArraySet.unmodifiableSet(CharArraySet.copy(matchVersion, stemExclusionSet));
    }
  
    /**
     * Builds an analyzer with the given stop words.
     * @deprecated use {@link #GermanAnalyzer(Version, Set)}
     */
    @Deprecated
    public GermanAnalyzer(Version matchVersion, String... stopwords) {
      this(matchVersion, StopFilter.makeStopSet(matchVersion, stopwords));
    }
  
    /**
     * Builds an analyzer with the given stop words.
     * @deprecated use {@link #GermanAnalyzer(Version, Set)}
     */
    @Deprecated
    public GermanAnalyzer(Version matchVersion, Map<?,?> stopwords) {
      this(matchVersion, stopwords.keySet());
      
    }
  
    /**
     * Builds an analyzer with the given stop words.
     * @deprecated use {@link #GermanAnalyzer(Version, Set)}
     */
    @Deprecated
    public GermanAnalyzer(Version matchVersion, File stopwords) throws IOException {
      this(matchVersion, WordlistLoader.getWordSet(
          IOUtils.getDecodingReader(stopwords, IOUtils.CHARSET_UTF_8), matchVersion));
    }
  
    /**
     * Builds an exclusionlist from an array of Strings.
     * @deprecated use {@link #GermanAnalyzer(Version, Set, Set)} instead
     */
    @Deprecated
    public void setStemExclusionTable(String[] exclusionlist) {
      exclusionSet = StopFilter.makeStopSet(matchVersion, exclusionlist);
      setPreviousTokenStream(null); // force a new stemmer to be created
    }
  
    /**
     * Builds an exclusionlist from a {@link Map}
     * @deprecated use {@link #GermanAnalyzer(Version, Set, Set)} instead
     */
    @Deprecated
    public void setStemExclusionTable(Map<?,?> exclusionlist) {
      exclusionSet = new HashSet<Object>(exclusionlist.keySet());
      setPreviousTokenStream(null); // force a new stemmer to be created
    }
  
    /**
     * Builds an exclusionlist from the words contained in the given file.
     * @deprecated use {@link #GermanAnalyzer(Version, Set, Set)} instead
     */
    @Deprecated
    public void setStemExclusionTable(File exclusionlist) throws IOException {
      exclusionSet = WordlistLoader.getWordSet(IOUtils.getDecodingReader(exclusionlist,
          IOUtils.CHARSET_UTF_8), matchVersion);
      setPreviousTokenStream(null); // force a new stemmer to be created
    }
  
    /**
     * Creates
     * {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
     * used to tokenize all the text in the provided {@link Reader}.
     * 
     * @return {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
     *         built from a {@link StandardTokenizer} filtered with
     *         {@link StandardFilter}, {@link LowerCaseFilter}, {@link StopFilter}
     *         , {@link KeywordMarkerFilter} if a stem exclusion set is
     *         provided, and {@link SnowballFilter}
     */
    @Override
    protected TokenStreamComponents createComponents(String fieldName,
        Reader reader) {
      final Tokenizer source = new StandardTokenizer(matchVersion, reader);
      TokenStream result = new StandardFilter(matchVersion, source);
      result = new LowerCaseFilter(matchVersion, result);
      result = new StopFilter( matchVersion, result, stopwords);
      result = new KeywordMarkerFilter(result, exclusionSet);
      if (matchVersion.onOrAfter(Version.LUCENE_31))
        result = new SnowballFilter(result, new German2Stemmer());
      else
        result = new GermanStemFilter(result);
      return new TokenStreamComponents(source, result);
    }
  }
  