content: 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</a>
     * @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;
    }
  }
  