Stemmer.java

/**
 *  OpenKM, Open Document Management System (http://www.openkm.com)
 *  Copyright (c) 2006-2011  Paco Avila & Josep Llort
 *
 *  No bytes were intentionally harmed during the development of this application.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package com.openkm.kea.stemmers;

import java.io.*;

/**
 * Abstract class for stemmers.
 *
 * @author Eibe Frank (eibe@cs.waikato.ac.nz)
 * @version 1.0
 */
public abstract class Stemmer implements Serializable {

	private static final long serialVersionUID = 1L;

/**
   * Iterated stemming of the given word.
   */
  public abstract String stem(String str);

  /**
   * Stems everything in the given string.
   */
  public String stemString(String str) {
      str = str.toLowerCase();
      StringBuffer result = new StringBuffer();
      int start = -1;
      for (int j = 0; j < str.length(); j++) {
	  char c = str.charAt(j);
	  if (Character.isLetterOrDigit(c)) {
	      if (start == -1) {
		  start = j;
	      }
	  } else if (c == '\'') {
	      if (start == -1) {
		  result.append(c);
	      }
	  } else {
	      if (start != -1) {
		  result.append(stem(str.substring(start, j)));
		  start = -1;
	      }
	      result.append(c);
	  }
      }
      if (start != -1) {
	  result.append(stem(str.substring(start, str.length())));
      }
      return result.toString();  
  }
}