org.apache.lucene.analysis.miscellaneous.RemoveDuplicatesTokenFilter Maven / Gradle / Ivy
/*
* 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.
*/
package org.apache.lucene.analysis.miscellaneous;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.analysis.CharArraySet;
import java.io.IOException;
/**
* A TokenFilter which filters out Tokens at the same position and Term text as the previous token in the stream.
*/
public final class RemoveDuplicatesTokenFilter extends TokenFilter {
private final CharTermAttribute termAttribute = addAttribute(CharTermAttribute.class);
private final PositionIncrementAttribute posIncAttribute = addAttribute(PositionIncrementAttribute.class);
private final CharArraySet previous = new CharArraySet(8, false);
/**
* Creates a new RemoveDuplicatesTokenFilter
*
* @param in TokenStream that will be filtered
*/
public RemoveDuplicatesTokenFilter(TokenStream in) {
super(in);
}
@Override
public boolean incrementToken() throws IOException {
while (input.incrementToken()) {
final char term[] = termAttribute.buffer();
final int length = termAttribute.length();
final int posIncrement = posIncAttribute.getPositionIncrement();
if (posIncrement > 0) {
previous.clear();
}
boolean duplicate = (posIncrement == 0 && previous.contains(term, 0, length));
// clone the term, and add to the set of seen terms.
char saved[] = new char[length];
System.arraycopy(term, 0, saved, 0, length);
previous.add(saved);
if (!duplicate) {
return true;
}
}
return false;
}
@Override
public void reset() throws IOException {
super.reset();
previous.clear();
}
}