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Lucene example source code file (HungarianLightStemmer.java)

This example Lucene source code file (HungarianLightStemmer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

hungarianlightstemmer, hungarianlightstemmer, suppresswarnings, suppresswarnings

The Lucene HungarianLightStemmer.java source code

package org.apache.lucene.analysis.hu;

/**
 * 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.
 */

/* 
 * This algorithm is updated based on code located at:
 * http://members.unine.ch/jacques.savoy/clef/
 * 
 * Full copyright for that code follows:
 */

/*
 * Copyright (c) 2005, Jacques Savoy
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this 
 * list of conditions and the following disclaimer. Redistributions in binary 
 * form must reproduce the above copyright notice, this list of conditions and
 * the following disclaimer in the documentation and/or other materials 
 * provided with the distribution. Neither the name of the author nor the names 
 * of its contributors may be used to endorse or promote products derived from 
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

import static org.apache.lucene.analysis.util.StemmerUtil.*;

/**
 * Light Stemmer for Hungarian.
 * <p>
 * This stemmer implements the "UniNE" algorithm in:
 * <i>Light Stemming Approaches for the French, Portuguese, German and Hungarian Languages
 * Jacques Savoy
 */
public class HungarianLightStemmer {
  public int stem(char s[], int len) {
    for (int i = 0; i < len; i++)
      switch(s[i]) {
        case 'á': s[i] = 'a'; break;
        case 'ë':
        case 'é': s[i] = 'e'; break;
        case 'í': s[i] = 'i'; break;
        case 'ó':
        case 'ő':
        case 'õ':
        case 'ö': s[i] = 'o'; break;
        case 'ú':
        case 'ű':
        case 'ũ':
        case 'û':
        case 'ü': s[i] = 'u'; break;
      }
    
    len = removeCase(s, len);
    len = removePossessive(s, len);
    len = removePlural(s, len);
    return normalize(s, len);
  }
  
  private int removeCase(char s[], int len) {
    if (len > 6 && endsWith(s, len, "kent"))
      return len - 4;
    
    if (len > 5) {
      if (endsWith(s, len, "nak") ||
          endsWith(s, len, "nek") ||
          endsWith(s, len, "val") ||
          endsWith(s, len, "vel") ||
          endsWith(s, len, "ert") ||
          endsWith(s, len, "rol") ||
          endsWith(s, len, "ban") ||
          endsWith(s, len, "ben") ||
          endsWith(s, len, "bol") ||
          endsWith(s, len, "nal") ||
          endsWith(s, len, "nel") ||
          endsWith(s, len, "hoz") ||
          endsWith(s, len, "hez") ||
          endsWith(s, len, "tol"))
        return len - 3;
      
      if (endsWith(s, len, "al") || endsWith(s, len, "el")) {
        if (!isVowel(s[len-3]) && s[len-3] == s[len-4])
          return len - 3;
      }
    }
    
    if (len > 4) {
      if (endsWith(s, len, "at") ||
          endsWith(s, len, "et") ||
          endsWith(s, len, "ot") ||
          endsWith(s, len, "va") ||
          endsWith(s, len, "ve") ||
          endsWith(s, len, "ra") ||
          endsWith(s, len, "re") ||
          endsWith(s, len, "ba") ||
          endsWith(s, len, "be") ||
          endsWith(s, len, "ul") ||
          endsWith(s, len, "ig"))
        return len - 2;
      
      if ((endsWith(s, len, "on") || endsWith(s, len, "en")) && !isVowel(s[len-3]))
          return len - 2;
      
      switch(s[len-1]) {
        case 't':
        case 'n': return len - 1;
        case 'a':
        case 'e': if (s[len-2] == s[len-3] && !isVowel(s[len-2])) return len - 2;
      }
    }
    
    return len;
  }

  private int removePossessive(char s[], int len) {
    if (len > 6) {
      if (!isVowel(s[len-5]) && 
         (endsWith(s, len, "atok") || 
          endsWith(s, len, "otok") || 
          endsWith(s, len, "etek")))
        return len - 4;
      
      if (endsWith(s, len, "itek") || endsWith(s, len, "itok"))
        return len - 4;
    }
    
    if (len > 5) {
      if (!isVowel(s[len-4]) &&
        (endsWith(s, len, "unk") ||
         endsWith(s, len, "tok") ||
         endsWith(s, len, "tek")))
        return len - 3;
      
      if (isVowel(s[len-4]) && endsWith(s, len, "juk"))
        return len - 3;
      
      if (endsWith(s, len, "ink"))
        return len - 3;
    }
    
    if (len > 4) {
      if (!isVowel(s[len-3]) &&
         (endsWith(s, len, "am") ||
          endsWith(s, len, "em") ||
          endsWith(s, len, "om") ||
          endsWith(s, len, "ad") ||
          endsWith(s, len, "ed") ||
          endsWith(s, len, "od") ||
          endsWith(s, len, "uk")))
        return len - 2;
      
      if (isVowel(s[len-3]) &&
         (endsWith(s, len, "nk") ||
          endsWith(s, len, "ja") ||
          endsWith(s, len, "je")))
        return len - 2;
      
      if (endsWith(s, len, "im") ||
          endsWith(s, len, "id") ||
          endsWith(s, len, "ik"))
        return len - 2;
    }
    
    if (len > 3)
      switch(s[len-1]) {
        case 'a':
        case 'e': if (!isVowel(s[len-2])) return len - 1; break;
        case 'm':
        case 'd': if (isVowel(s[len-2])) return len - 1; break;
        case 'i': return len - 1;
      }
    
    return len;
  }

  @SuppressWarnings("fallthrough")
  private int removePlural(char s[], int len) {
    if (len > 3 && s[len-1] == 'k')
      switch(s[len-2]) {
        case 'a':
        case 'o':
        case 'e': if (len > 4) return len - 2; /* intentional fallthru */
        default: return len - 1;
      }
    return len;
  }

  private int normalize(char s[], int len) {
    if (len > 3)
      switch(s[len-1]) {
        case 'a':
        case 'e':
        case 'i':
        case 'o': return len - 1;
      }
    return len;
  }

  private boolean isVowel(char ch) {
    switch(ch) {
      case 'a':
      case 'e':
      case 'i':
      case 'o':
      case 'u':
      case 'y': return true;
      default: return false;
    }
  }
}

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