Stemmer.java

package 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 {

  /**
   * 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();  
  }
}