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Lucene example source code file (PhrasePositions.java)

This example Lucene source code file (PhrasePositions.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

io, ioexception, ioexception, phrasepositions, phrasepositions, termpositions, termpositions

The Lucene PhrasePositions.java source code

package org.apache.lucene.search;

/**
 * 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.IOException;
import org.apache.lucene.index.*;

/**
 * Position of a term in a document that takes into account the term offset within the phrase. 
 */
final class PhrasePositions {
  int doc;					  // current doc
  int position;					  // position in doc
  int count;					  // remaining pos in this doc
  int offset;					  // position in phrase
  final int ord;                                  // unique across all PhrasePositions instances
  TermPositions tp;				  // stream of positions
  PhrasePositions next;				  // used to make lists
  boolean repeats;       // there's other pp for same term (e.g. query="1st word 2nd word"~1) 

  PhrasePositions(TermPositions t, int o, int ord) {
    tp = t;
    offset = o;
    this.ord = ord;
  }

  final boolean next() throws IOException {	  // increments to next doc
    if (!tp.next()) {
      tp.close();				  // close stream
      doc = Integer.MAX_VALUE;			  // sentinel value
      return false;
    }
    doc = tp.doc();
    position = 0;
    return true;
  }

  final boolean skipTo(int target) throws IOException {
    if (!tp.skipTo(target)) {
      tp.close();				  // close stream
      doc = Integer.MAX_VALUE;			  // sentinel value
      return false;
    }
    doc = tp.doc();
    position = 0;
    return true;
  }


  final void firstPosition() throws IOException {
    count = tp.freq();				  // read first pos
    nextPosition();
  }

  /**
   * Go to next location of this term current document, and set 
   * <code>position as location - offset, so that a 
   * matching exact phrase is easily identified when all PhrasePositions 
   * have exactly the same <code>position.
   */
  final boolean nextPosition() throws IOException {
    if (count-- > 0) {				  // read subsequent pos's
      position = tp.nextPosition() - offset;
      return true;
    } else
      return false;
  }
}

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