content: package org.apache.lucene.analysis.standard;
  
  /**
   * 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.TokenFilter;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
  import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
  import org.apache.lucene.util.Version;
  
  /**
   * Normalizes tokens extracted with {@link StandardTokenizer}.
   */
  public class StandardFilter extends TokenFilter {
    private final Version matchVersion;
    
    /** @deprecated Use {@link #StandardFilter(Version, TokenStream)} instead. */
    @Deprecated
    public StandardFilter(TokenStream in) {
      this(Version.LUCENE_30, in);
    }
    
    public StandardFilter(Version matchVersion, TokenStream in) {
      super(in);
      this.matchVersion = matchVersion;
    }
    
    private static final String APOSTROPHE_TYPE = ClassicTokenizer.TOKEN_TYPES[ClassicTokenizer.APOSTROPHE];
    private static final String ACRONYM_TYPE = ClassicTokenizer.TOKEN_TYPES[ClassicTokenizer.ACRONYM];
  
    // this filters uses attribute type
    private final TypeAttribute typeAtt = addAttribute(TypeAttribute.class);
    private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
    
    @Override
    public final boolean incrementToken() throws IOException {
      if (matchVersion.onOrAfter(Version.LUCENE_31))
        return input.incrementToken(); // TODO: add some niceties for the new grammar
      else
        return incrementTokenClassic();
    }
    
    public final boolean incrementTokenClassic() throws IOException {
      if (!input.incrementToken()) {
        return false;
      }
  
      final char[] buffer = termAtt.buffer();
      final int bufferLength = termAtt.length();
      final String type = typeAtt.type();
  
      if (type == APOSTROPHE_TYPE &&      // remove 's
          bufferLength >= 2 &&
          buffer[bufferLength-2] == '\'' &&
          (buffer[bufferLength-1] == 's' || buffer[bufferLength-1] == 'S')) {
        // Strip last 2 characters off
        termAtt.setLength(bufferLength - 2);
      } else if (type == ACRONYM_TYPE) {      // remove dots
        int upto = 0;
        for(int i=0;i<bufferLength;i++) {
          char c = buffer[i];
          if (c != '.')
            buffer[upto++] = c;
        }
        termAtt.setLength(upto);
      }
  
      return true;
    }
  }
  