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Lucene example source code file (LowerCaseFilter.java)

This example Lucene source code file (LowerCaseFilter.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

characterutils, characterutils, chartermattribute, deprecated, io, ioexception, ioexception, lowercasefilter, lowercasefilter, override, tokenfilter, tokenstream, tokenstream

The Lucene LowerCaseFilter.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.IOException;

import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.util.CharacterUtils;
import org.apache.lucene.util.Version;

/**
 * Normalizes token text to lower case.
 * <a name="version"/>
 * <p>You must specify the required {@link Version}
 * compatibility when creating LowerCaseFilter:
 * <ul>
 *   <li> As of 3.1, supplementary characters are properly lowercased.
 * </ul>
 */
public final class LowerCaseFilter extends TokenFilter {
  private final CharacterUtils charUtils;
  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
  
  /**
   * Create a new LowerCaseFilter, that normalizes token text to lower case.
   * 
   * @param matchVersion See <a href="#version">above
   * @param in TokenStream to filter
   */
  public LowerCaseFilter(Version matchVersion, TokenStream in) {
    super(in);
    charUtils = CharacterUtils.getInstance(matchVersion);
  }
  
  /**
   * @deprecated Use {@link #LowerCaseFilter(Version, TokenStream)} instead.
   */
  @Deprecated
  public LowerCaseFilter(TokenStream in) {
    this(Version.LUCENE_30, in);
  }

  @Override
  public final boolean incrementToken() throws IOException {
    if (input.incrementToken()) {
      final char[] buffer = termAtt.buffer();
      final int length = termAtt.length();
      for (int i = 0; i < length;) {
       i += Character.toChars(
               Character.toLowerCase(
                   charUtils.codePointAt(buffer, i)), buffer, i);
      }
      return true;
    } else
      return false;
  }
}

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