package org.apache.lucene.analysis;
/**
* 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.
*/
import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.util.Arrays;
import java.util.Set;
import java.util.List;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.Version;
/** Filters {@link LetterTokenizer} with {@link LowerCaseFilter} and {@link StopFilter}.
*
* <a name="version"/>
* <p>You must specify the required {@link Version}
* compatibility when creating StopAnalyzer:
* <ul>
* <li> As of 3.1, StopFilter correctly handles Unicode 4.0
* supplementary characters in stopwords
* <li> As of 2.9, position increments are preserved
* </ul>
*/
public final class StopAnalyzer extends StopwordAnalyzerBase {
/** An unmodifiable set containing some common English words that are not usually useful
for searching.*/
public static final Set<?> ENGLISH_STOP_WORDS_SET;
static {
final List<String> stopWords = Arrays.asList(
"a", "an", "and", "are", "as", "at", "be", "but", "by",
"for", "if", "in", "into", "is", "it",
"no", "not", "of", "on", "or", "such",
"that", "the", "their", "then", "there", "these",
"they", "this", "to", "was", "will", "with"
);
final CharArraySet stopSet = new CharArraySet(Version.LUCENE_CURRENT,
stopWords.size(), false);
stopSet.addAll(stopWords);
ENGLISH_STOP_WORDS_SET = CharArraySet.unmodifiableSet(stopSet);
}
/** Builds an analyzer which removes words in
* {@link #ENGLISH_STOP_WORDS_SET}.
* @param matchVersion See <a href="#version">above</a>
*/
public StopAnalyzer(Version matchVersion) {
this(matchVersion, ENGLISH_STOP_WORDS_SET);
}
/** Builds an analyzer with the stop words from the given set.
* @param matchVersion See <a href="#version">above</a>
* @param stopWords Set of stop words */
public StopAnalyzer(Version matchVersion, Set<?> stopWords) {
super(matchVersion, stopWords);
}
/** Builds an analyzer with the stop words from the given file.
* @see WordlistLoader#getWordSet(Reader, Version)
* @param matchVersion See <a href="#version">above</a>
* @param stopwordsFile File to load stop words from */
public StopAnalyzer(Version matchVersion, File stopwordsFile) throws IOException {
this(matchVersion, WordlistLoader.getWordSet(IOUtils.getDecodingReader(stopwordsFile,
IOUtils.CHARSET_UTF_8), matchVersion));
}
/** Builds an analyzer with the stop words from the given reader.
* @see WordlistLoader#getWordSet(Reader, Version)
* @param matchVersion See <a href="#version">above</a>
* @param stopwords Reader to load stop words from */
public StopAnalyzer(Version matchVersion, Reader stopwords) throws IOException {
this(matchVersion, WordlistLoader.getWordSet(stopwords, matchVersion));
}
/**
* Creates
* {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
* used to tokenize all the text in the provided {@link Reader}.
*
* @return {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
* built from a {@link LowerCaseTokenizer} filtered with
* {@link StopFilter}
*/
@Override
protected TokenStreamComponents createComponents(String fieldName,
Reader reader) {
final Tokenizer source = new LowerCaseTokenizer(matchVersion, reader);
return new TokenStreamComponents(source, new StopFilter(matchVersion,
source, stopwords));
}
}