src/java/org/apache/lucene/analysis/standard/StandardFilter.java

package org.apache.lucene.analysis.standard;

/* ====================================================================
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 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
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 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
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 *    if and wherever such third-party acknowledgments normally appear.
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 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import org.apache.lucene.analysis.*;

/** Normalizes tokens extracted with {@link StandardTokenizer}. */

public final class StandardFilter extends TokenFilter
  implements StandardTokenizerConstants  {


  /** Construct filtering <i>in</i>. */
  public StandardFilter(TokenStream in) {
    input = in;
  }

  private static final String APOSTROPHE_TYPE = tokenImage[APOSTROPHE];
  private static final String ACRONYM_TYPE = tokenImage[ACRONYM];
  
  /** Returns the next token in the stream, or null at EOS.
   * <p>Removes <tt>'s</tt> from the end of words.
   * <p>Removes dots from acronyms.
   */
  public final org.apache.lucene.analysis.Token next() throws java.io.IOException {
    org.apache.lucene.analysis.Token t = input.next();

    if (t == null)
      return null;

    String text = t.termText();
    String type = t.type();

    if (type == APOSTROPHE_TYPE &&		  // remove 's
	(text.endsWith("'s") || text.endsWith("'S"))) {
      return new org.apache.lucene.analysis.Token
	(text.substring(0,text.length()-2),
	 t.startOffset(), t.endOffset(), type);

    } else if (type == ACRONYM_TYPE) {		  // remove dots
      StringBuffer trimmed = new StringBuffer();
      for (int i = 0; i < text.length(); i++) {
	char c = text.charAt(i);
	if (c != '.')
	  trimmed.append(c);
      }
      return new org.apache.lucene.analysis.Token
	(trimmed.toString(), t.startOffset(), t.endOffset(), type);

    } else {
      return t;
    }
  }
}