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Lucene example source code file (StopwordAnalyzerBase.java)

This example Lucene source code file (StopwordAnalyzerBase.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, class, io, ioexception, reusableanalyzerbase, set, set, stopwordanalyzerbase, stopwordanalyzerbase, string, util, version, version

The Lucene StopwordAnalyzerBase.java source code

/**
 * 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.
 */

package org.apache.lucene.analysis;

import java.io.IOException;
import java.util.Set;

import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.ReusableAnalyzerBase;
import org.apache.lucene.analysis.WordlistLoader;
import org.apache.lucene.util.Version;

/**
 * Base class for Analyzers that need to make use of stopword sets. 
 * 
 */
public abstract class StopwordAnalyzerBase extends ReusableAnalyzerBase {

  /**
   * An immutable stopword set
   */
  protected final CharArraySet stopwords;

  protected final Version matchVersion;

  /**
   * Returns the analyzer's stopword set or an empty set if the analyzer has no
   * stopwords
   * 
   * @return the analyzer's stopword set or an empty set if the analyzer has no
   *         stopwords
   */
  public Set<?> getStopwordSet() {
    return stopwords;
  }

  /**
   * Creates a new instance initialized with the given stopword set
   * 
   * @param version
   *          the Lucene version for cross version compatibility
   * @param stopwords
   *          the analyzer's stopword set
   */
  protected StopwordAnalyzerBase(final Version version, final Set<?> stopwords) {
    matchVersion = version;
    // analyzers should use char array set for stopwords!
    this.stopwords = stopwords == null ? CharArraySet.EMPTY_SET : CharArraySet
        .unmodifiableSet(CharArraySet.copy(version, stopwords));
  }

  /**
   * Creates a new Analyzer with an empty stopword set
   * 
   * @param version
   *          the Lucene version for cross version compatibility
   */
  protected StopwordAnalyzerBase(final Version version) {
    this(version, null);
  }

  /**
   * Creates a CharArraySet from a file resource associated with a class. (See
   * {@link Class#getResourceAsStream(String)}).
   * 
   * @param ignoreCase
   *          <code>true if the set should ignore the case of the
   *          stopwords, otherwise <code>false
   * @param aClass
   *          a class that is associated with the given stopwordResource
   * @param resource
   *          name of the resource file associated with the given class
   * @param comment
   *          comment string to ignore in the stopword file
   * @return a CharArraySet containing the distinct stopwords from the given
   *         file
   * @throws IOException
   *           if loading the stopwords throws an {@link IOException}
   */
  protected static CharArraySet loadStopwordSet(final boolean ignoreCase,
      final Class<? extends ReusableAnalyzerBase> aClass, final String resource,
      final String comment) throws IOException {
    final Set<String> wordSet = WordlistLoader.getWordSet(aClass, resource,
        comment);
    final CharArraySet set = new CharArraySet(Version.LUCENE_31, wordSet.size(), ignoreCase);
    set.addAll(wordSet);
    return set;
  }

}

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