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Lucene example source code file (ElisionFilter.java)

This example Lucene source code file (ElisionFilter.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

chararrayset, chararrayset, chartermattribute, default_articles, deprecated, deprecated, elisionfilter, elisionfilter, io, ioexception, override, set, set, tokenfilter, tokenstream, util

The Lucene ElisionFilter.java source code

package org.apache.lucene.analysis.fr;

/**
 * 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.Set;
import java.util.Arrays;
import org.apache.lucene.analysis.standard.StandardTokenizer; // for javadocs
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.util.Version;

/**
 * Removes elisions from a {@link TokenStream}. For example, "l'avion" (the plane) will be
 * tokenized as "avion" (plane).
 * 
 * @see <a href="http://fr.wikipedia.org/wiki/%C3%89lision">Elision in Wikipedia
 */
public final class ElisionFilter extends TokenFilter {
  private CharArraySet articles = CharArraySet.EMPTY_SET;
  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
  private static final CharArraySet DEFAULT_ARTICLES = CharArraySet.unmodifiableSet(
      new CharArraySet(Version.LUCENE_CURRENT, Arrays.asList(
          "l", "m", "t", "qu", "n", "s", "j"), true));
  
  private static char[] apostrophes = {'\'', '\u2019'};
  
  /**
   * Set the stopword articles
   * @param matchVersion the lucene backwards compatibility version
   * @param articles a set of articles
   * @deprecated use {@link #ElisionFilter(Version, TokenStream, Set)} instead
   */
  @Deprecated
  public void setArticles(Version matchVersion, Set<?> articles) {
    this.articles = CharArraySet.unmodifiableSet(
        CharArraySet.copy(matchVersion, articles));
  }

  /**
   * Set the stopword articles
   * @param articles a set of articles
   * @deprecated use {@link #setArticles(Version, Set)} instead
   */
  @Deprecated
  public void setArticles(Set<?> articles) {
    setArticles(Version.LUCENE_CURRENT, articles);
  }
  /**
   * Constructs an elision filter with standard stop words
   */
  public ElisionFilter(Version matchVersion, TokenStream input) {
    this(matchVersion, input, DEFAULT_ARTICLES);
  }

  /**
   * Constructs an elision filter with standard stop words
   * @deprecated use {@link #ElisionFilter(Version, TokenStream)} instead
   */
  @Deprecated
  public ElisionFilter(TokenStream input) {
    this(Version.LUCENE_30, input);
  }

  /**
   * Constructs an elision filter with a Set of stop words
   * @deprecated use {@link #ElisionFilter(Version, TokenStream, Set)} instead
   */
  @Deprecated
  public ElisionFilter(TokenStream input, Set<?> articles) {
    this(Version.LUCENE_30, input, articles);
  }
  
  /**
   * Constructs an elision filter with a Set of stop words
   * @param matchVersion the lucene backwards compatibility version
   * @param input the source {@link TokenStream}
   * @param articles a set of stopword articles
   */
  public ElisionFilter(Version matchVersion, TokenStream input, Set<?> articles) {
    super(input);
    this.articles = CharArraySet.unmodifiableSet(
        new CharArraySet(matchVersion, articles, true));
  }

  /**
   * Constructs an elision filter with an array of stop words
   * @deprecated use {@link #ElisionFilter(Version, TokenStream, Set)} instead
   */
  @Deprecated
  public ElisionFilter(TokenStream input, String[] articles) {
    this(Version.LUCENE_CURRENT, input,
        new CharArraySet(Version.LUCENE_CURRENT,
            Arrays.asList(articles), true));
  }

  /**
   * Increments the {@link TokenStream} with a {@link CharTermAttribute} without elisioned start
   */
  @Override
  public final boolean incrementToken() throws IOException {
    if (input.incrementToken()) {
      char[] termBuffer = termAtt.buffer();
      int termLength = termAtt.length();

      int minPoz = Integer.MAX_VALUE;
      for (int i = 0; i < apostrophes.length; i++) {
        char apos = apostrophes[i];
        // The equivalent of String.indexOf(ch)
        for (int poz = 0; poz < termLength ; poz++) {
          if (termBuffer[poz] == apos) {
            minPoz = Math.min(poz, minPoz);
            break;
          }
        }
      }

      // An apostrophe has been found. If the prefix is an article strip it off.
      if (minPoz != Integer.MAX_VALUE
          && articles.contains(termAtt.buffer(), 0, minPoz)) {
        termAtt.copyBuffer(termAtt.buffer(), minPoz + 1, termAtt.length() - (minPoz + 1));
      }

      return true;
    } else {
      return false;
    }
  }
}

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