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package org.apache.lucene.analysis.miscellaneous;
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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 org.apache.lucene.analysis.CharArrayMap;
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import org.apache.lucene.analysis.TokenFilter;
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import org.apache.lucene.analysis.TokenStream;
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import org.apache.lucene.analysis.tokenattributes.KeywordAttribute;
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import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
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import org.apache.lucene.util.Version;
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* Provides the ability to override any {@link KeywordAttribute} aware stemmer
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* with custom dictionary-based stemming.
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public final class StemmerOverrideFilter extends TokenFilter {
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private final CharArrayMap<String> dictionary;
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private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
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private final KeywordAttribute keywordAtt = addAttribute(KeywordAttribute.class);
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* Create a new StemmerOverrideFilter, performing dictionary-based stemming
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* with the provided <code>dictionary</code>.
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* Any dictionary-stemmed terms will be marked with {@link KeywordAttribute}
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* so that they will not be stemmed with stemmers down the chain.
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public StemmerOverrideFilter(Version matchVersion, TokenStream input,
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Map<?,String> dictionary) {
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this.dictionary = dictionary instanceof CharArrayMap ?
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(CharArrayMap<String>) dictionary : CharArrayMap.copy(matchVersion, dictionary);
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public boolean incrementToken() throws IOException {
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if (input.incrementToken()) {
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if (!keywordAtt.isKeyword()) { // don't muck with already-keyworded terms
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String stem = dictionary.get(termAtt.buffer(), 0, termAtt.length());
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termAtt.setEmpty().append(stem);
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keywordAtt.setKeyword(true);