Lucene example source code file (StopAnalyzer.java)

This example Lucene source code file (StopAnalyzer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

english_stop_words_set, english_stop_words_set, file, io, ioexception, ioexception, lowercasetokenizer, reader, reader, set, stopanalyzer, stopanalyzer, stopfilter, stopwordanalyzerbase, tokenstreamcomponents, util

The Lucene StopAnalyzer.java source code

package org.apache.lucene.analysis;

/**
 * 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.Set;
import java.util.List;

import org.apache.lucene.util.Version;

/** Filters {@link LetterTokenizer} with {@link LowerCaseFilter} and {@link StopFilter}.
 *
 * <a name="version"/>
 * <p>You must specify the required {@link Version}
 * compatibility when creating StopAnalyzer:
 * <ul>
 *    <li> As of 3.1, StopFilter correctly handles Unicode 4.0
 *         supplementary characters in stopwords
 *   <li> As of 2.9, position increments are preserved
 * </ul>
*/

public final class StopAnalyzer extends StopwordAnalyzerBase {
  
  /** An unmodifiable set containing some common English words that are not usually useful
  for searching.*/
  public static final Set<?> ENGLISH_STOP_WORDS_SET;
  
  static {
    final List<String> stopWords = Arrays.asList(
      "a", "an", "and", "are", "as", "at", "be", "but", "by",
      "for", "if", "in", "into", "is", "it",
      "no", "not", "of", "on", "or", "such",
      "that", "the", "their", "then", "there", "these",
      "they", "this", "to", "was", "will", "with"
    );
    final CharArraySet stopSet = new CharArraySet(Version.LUCENE_CURRENT, 
        stopWords.size(), false);
    stopSet.addAll(stopWords);  
    ENGLISH_STOP_WORDS_SET = CharArraySet.unmodifiableSet(stopSet); 
  }
  
  /** Builds an analyzer which removes words in
   *  {@link #ENGLISH_STOP_WORDS_SET}.
   * @param matchVersion See <a href="#version">above
   */
  public StopAnalyzer(Version matchVersion) {
    this(matchVersion, ENGLISH_STOP_WORDS_SET);
  }

  /** Builds an analyzer with the stop words from the given set.
   * @param matchVersion See <a href="#version">above
   * @param stopWords Set of stop words */
  public StopAnalyzer(Version matchVersion, Set<?> stopWords) {
    super(matchVersion, stopWords);
  }

  /** Builds an analyzer with the stop words from the given file.
   * @see WordlistLoader#getWordSet(File)
   * @param matchVersion See <a href="#version">above
   * @param stopwordsFile File to load stop words from */
  public StopAnalyzer(Version matchVersion, File stopwordsFile) throws IOException {
    this(matchVersion, WordlistLoader.getWordSet(stopwordsFile));
  }

  /** Builds an analyzer with the stop words from the given reader.
   * @see WordlistLoader#getWordSet(Reader)
   * @param matchVersion See <a href="#version">above
   * @param stopwords Reader to load stop words from */
  public StopAnalyzer(Version matchVersion, Reader stopwords) throws IOException {
    this(matchVersion, WordlistLoader.getWordSet(stopwords));
  }

  /**
   * 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 LowerCaseTokenizer} filtered with
   *         {@link StopFilter}
   */
  @Override
  protected TokenStreamComponents createComponents(String fieldName,
      Reader reader) {
    final Tokenizer source = new LowerCaseTokenizer(matchVersion, reader);
    return new TokenStreamComponents(source, new StopFilter(matchVersion,
          source, stopwords));
  }
}