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package org.apache.lucene.analysis.fa;
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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import java.io.IOException;
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import java.io.Reader;
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import java.util.Hashtable;
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import org.apache.lucene.analysis.Analyzer;
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import org.apache.lucene.analysis.LowerCaseFilter;
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import org.apache.lucene.analysis.StopFilter;
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import org.apache.lucene.analysis.StopwordAnalyzerBase;
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import org.apache.lucene.analysis.CharReader;
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import org.apache.lucene.analysis.TokenStream;
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import org.apache.lucene.analysis.Tokenizer;
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import org.apache.lucene.analysis.WordlistLoader;
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import org.apache.lucene.analysis.ar.ArabicLetterTokenizer;
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import org.apache.lucene.analysis.ar.ArabicNormalizationFilter;
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import org.apache.lucene.analysis.standard.StandardTokenizer;
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import org.apache.lucene.util.IOUtils;
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import org.apache.lucene.util.Version;
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* {@link Analyzer} for Persian.
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* This Analyzer uses {@link ArabicLetterTokenizer} which implies tokenizing around
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* zero-width non-joiner in addition to whitespace. Some persian-specific variant forms (such as farsi
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* yeh and keheh) are standardized. "Stemming" is accomplished via stopwords.
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public final class PersianAnalyzer extends StopwordAnalyzerBase {
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* File containing default Persian stopwords.
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* Default stopword list is from
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* http://members.unine.ch/jacques.savoy/clef/index.html The stopword list is
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public final static String DEFAULT_STOPWORD_FILE = "stopwords.txt";
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* The comment character in the stopwords file. All lines prefixed with this
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public static final String STOPWORDS_COMMENT = "#";
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* Returns an unmodifiable instance of the default stop-words set.
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* @return an unmodifiable instance of the default stop-words set.
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public static Set<?> getDefaultStopSet(){
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return DefaultSetHolder.DEFAULT_STOP_SET;
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* Atomically loads the DEFAULT_STOP_SET in a lazy fashion once the outer class
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* accesses the static final set the first time.;
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private static class DefaultSetHolder {
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static final Set<?> DEFAULT_STOP_SET;
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DEFAULT_STOP_SET = loadStopwordSet(false, PersianAnalyzer.class, DEFAULT_STOPWORD_FILE, STOPWORDS_COMMENT);
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} catch (IOException ex) {
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// default set should always be present as it is part of the
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throw new RuntimeException("Unable to load default stopword set");
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* Builds an analyzer with the default stop words:
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* {@link #DEFAULT_STOPWORD_FILE}.
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public PersianAnalyzer(Version matchVersion) {
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this(matchVersion, DefaultSetHolder.DEFAULT_STOP_SET);
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* Builds an analyzer with the given stop words
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* @param matchVersion
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* lucene compatibility version
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public PersianAnalyzer(Version matchVersion, Set<?> stopwords){
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super(matchVersion, stopwords);
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* Builds an analyzer with the given stop words.
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* @deprecated use {@link #PersianAnalyzer(Version, Set)} instead
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public PersianAnalyzer(Version matchVersion, String... stopwords) {
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this(matchVersion, StopFilter.makeStopSet(matchVersion, stopwords));
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* Builds an analyzer with the given stop words.
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* @deprecated use {@link #PersianAnalyzer(Version, Set)} instead
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public PersianAnalyzer(Version matchVersion, Hashtable<?, ?> stopwords) {
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this(matchVersion, stopwords.keySet());
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* Builds an analyzer with the given stop words. Lines can be commented out
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* using {@link #STOPWORDS_COMMENT}
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* @deprecated use {@link #PersianAnalyzer(Version, Set)} instead
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public PersianAnalyzer(Version matchVersion, File stopwords) throws IOException {
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this(matchVersion, WordlistLoader.getWordSet(
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IOUtils.getDecodingReader(stopwords, IOUtils.CHARSET_UTF_8),
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STOPWORDS_COMMENT, matchVersion));
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* {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
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* used to tokenize all the text in the provided {@link Reader}.
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* @return {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
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* built from a {@link StandardTokenizer} filtered with
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* {@link LowerCaseFilter}, {@link ArabicNormalizationFilter},
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* {@link PersianNormalizationFilter} and Persian Stop words
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protected TokenStreamComponents createComponents(String fieldName,
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final Tokenizer source;
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if (matchVersion.onOrAfter(Version.LUCENE_31)) {
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source = new StandardTokenizer(matchVersion, reader);
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source = new ArabicLetterTokenizer(matchVersion, reader);
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TokenStream result = new LowerCaseFilter(matchVersion, source);
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result = new ArabicNormalizationFilter(result);
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/* additional persian-specific normalization */
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result = new PersianNormalizationFilter(result);
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* the order here is important: the stopword list is normalized with the
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return new TokenStreamComponents(source, new StopFilter(matchVersion, result, stopwords));
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* Wraps the Reader with {@link PersianCharFilter}
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protected Reader initReader(Reader reader) {
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return matchVersion.onOrAfter(Version.LUCENE_31) ?
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new PersianCharFilter(CharReader.get(reader)) :