org.apache.lucene.analysis.de.GermanLightStemmer Maven / Gradle / Ivy
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package org.apache.lucene.analysis.de;
/*
* 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.
*/
/**
* Light Stemmer for German.
*
* This stemmer implements the "UniNE" algorithm in:
* Light Stemming Approaches for the French, Portuguese, German and Hungarian Languages
* Jacques Savoy
*/
public class GermanLightStemmer {
public int stem(char s[], int len) {
for (int i = 0; i < len; i++)
switch(s[i]) {
case 'ä':
case 'à':
case 'á':
case 'â': s[i] = 'a'; break;
case 'ö':
case 'ò':
case 'ó':
case 'ô': s[i] = 'o'; break;
case 'ï':
case 'ì':
case 'í':
case 'î': s[i] = 'i'; break;
case 'ü':
case 'ù':
case 'ú':
case 'û': s[i] = 'u'; break;
}
len = step1(s, len);
return step2(s, len);
}
private boolean stEnding(char ch) {
switch(ch) {
case 'b':
case 'd':
case 'f':
case 'g':
case 'h':
case 'k':
case 'l':
case 'm':
case 'n':
case 't': return true;
default: return false;
}
}
private int step1(char s[], int len) {
if (len > 5 && s[len-3] == 'e' && s[len-2] == 'r' && s[len-1] == 'n')
return len - 3;
if (len > 4 && s[len-2] == 'e')
switch(s[len-1]) {
case 'm':
case 'n':
case 'r':
case 's': return len - 2;
}
if (len > 3 && s[len-1] == 'e')
return len - 1;
if (len > 3 && s[len-1] == 's' && stEnding(s[len-2]))
return len - 1;
return len;
}
private int step2(char s[], int len) {
if (len > 5 && s[len-3] == 'e' && s[len-2] == 's' && s[len-1] == 't')
return len - 3;
if (len > 4 && s[len-2] == 'e' && (s[len-1] == 'r' || s[len-1] == 'n'))
return len - 2;
if (len > 4 && s[len-2] == 's' && s[len-1] == 't' && stEnding(s[len-3]))
return len - 2;
return len;
}
}