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Lucene example source code file (SimpleFragListBuilder.java)

This example Lucene source code file (SimpleFragListBuilder.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

arraylist, fieldfraglist, fieldfraglist, fraglistbuilder, illegalargumentexception, it, it, iterator, margin, margin, min_frag_char_size, min_frag_char_size, simplefraglistbuilder, util, weightedphraseinfo

The Lucene SimpleFragListBuilder.java source code

package org.apache.lucene.search.vectorhighlight;

 * 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.lucene.search.vectorhighlight.FieldPhraseList.WeightedPhraseInfo;

 * A simple implementation of {@link FragListBuilder}.
public class SimpleFragListBuilder implements FragListBuilder {
  public static final int MARGIN = 6;
  public static final int MIN_FRAG_CHAR_SIZE = MARGIN * 3;

  public FieldFragList createFieldFragList(FieldPhraseList fieldPhraseList, int fragCharSize) {
    if( fragCharSize < MIN_FRAG_CHAR_SIZE )
      throw new IllegalArgumentException( "fragCharSize(" + fragCharSize + ") is too small. It must be " +
          MIN_FRAG_CHAR_SIZE + " or higher." );

    FieldFragList ffl = new FieldFragList( fragCharSize );

    List<WeightedPhraseInfo> wpil = new ArrayList();
    Iterator<WeightedPhraseInfo> ite = fieldPhraseList.phraseList.iterator();
    WeightedPhraseInfo phraseInfo = null;
    int startOffset = 0;
    boolean taken = false;
    while( true ){
      if( !taken ){
        if( !ite.hasNext() ) break;
        phraseInfo = ite.next();
      taken = false;
      if( phraseInfo == null ) break;

      // if the phrase violates the border of previous fragment, discard it and try next phrase
      if( phraseInfo.getStartOffset() < startOffset ) continue;

      wpil.add( phraseInfo );
      int st = phraseInfo.getStartOffset() - MARGIN < startOffset ?
          startOffset : phraseInfo.getStartOffset() - MARGIN;
      int en = st + fragCharSize;
      if( phraseInfo.getEndOffset() > en )
        en = phraseInfo.getEndOffset();
      startOffset = en;

      while( true ){
        if( ite.hasNext() ){
          phraseInfo = ite.next();
          taken = true;
          if( phraseInfo == null ) break;
        if( phraseInfo.getEndOffset() <= en )
          wpil.add( phraseInfo );
      ffl.add( st, en, wpil );
    return ffl;


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