Lucene example source code file (QueryTermVector.java)

This example Lucene source code file (QueryTermVector.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, integer, integer, io, ioexception, list, list, override, querytermvector, querytermvector, string, string, stringbuilder, termfreqvector, tokenstream, util

The Lucene QueryTermVector.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 java.io.StringReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;

import java.util.List;
import java.util.Map;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.index.TermFreqVector;
import org.apache.lucene.util.ArrayUtil;

/**
 *
 *
 **/
public class QueryTermVector implements TermFreqVector {
  private String [] terms = new String[0];
  private int [] termFreqs = new int[0];

  public String getField() { return null;  }

  /**
   * 
   * @param queryTerms The original list of terms from the query, can contain duplicates
   */ 
  public QueryTermVector(String [] queryTerms) {

    processTerms(queryTerms);
  }

  public QueryTermVector(String queryString, Analyzer analyzer) {    
    if (analyzer != null)
    {
      TokenStream stream;
      try {
        stream = analyzer.reusableTokenStream("", new StringReader(queryString));
      } catch (IOException e1) {
        stream = null;
      }
      if (stream != null)
      {
        List<String> terms = new ArrayList();
        try {
          boolean hasMoreTokens = false;
          
          stream.reset(); 
          final CharTermAttribute termAtt = stream.addAttribute(CharTermAttribute.class);

          hasMoreTokens = stream.incrementToken();
          while (hasMoreTokens) {
            terms.add(termAtt.toString());
            hasMoreTokens = stream.incrementToken();
          }
          processTerms(terms.toArray(new String[terms.size()]));
        } catch (IOException e) {
        }
      }
    }                                                              
  }
  
  private void processTerms(String[] queryTerms) {
    if (queryTerms != null) {
      ArrayUtil.quickSort(queryTerms);
      Map<String,Integer> tmpSet = new HashMap(queryTerms.length);
      //filter out duplicates
      List<String> tmpList = new ArrayList(queryTerms.length);
      List<Integer> tmpFreqs = new ArrayList(queryTerms.length);
      int j = 0;
      for (int i = 0; i < queryTerms.length; i++) {
        String term = queryTerms[i];
        Integer position = tmpSet.get(term);
        if (position == null) {
          tmpSet.put(term, Integer.valueOf(j++));
          tmpList.add(term);
          tmpFreqs.add(Integer.valueOf(1));
        }       
        else {
          Integer integer = tmpFreqs.get(position.intValue());
          tmpFreqs.set(position.intValue(), Integer.valueOf(integer.intValue() + 1));          
        }
      }
      terms = tmpList.toArray(terms);
      //termFreqs = (int[])tmpFreqs.toArray(termFreqs);
      termFreqs = new int[tmpFreqs.size()];
      int i = 0;
      for (final Integer integer : tmpFreqs) {
        termFreqs[i++] = integer.intValue();
      }
    }
  }
  
  @Override
  public final String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append('{');
        for (int i=0; i<terms.length; i++) {
            if (i>0) sb.append(", ");
            sb.append(terms[i]).append('/').append(termFreqs[i]);
        }
        sb.append('}');
        return sb.toString();
    }
  

  public int size() {
    return terms.length;
  }

  public String[] getTerms() {
    return terms;
  }

  public int[] getTermFrequencies() {
    return termFreqs;
  }

  public int indexOf(String term) {
    int res = Arrays.binarySearch(terms, term);
        return res >= 0 ? res : -1;
  }

  public int[] indexesOf(String[] terms, int start, int len) {
    int res[] = new int[len];

    for (int i=0; i < len; i++) {
        res[i] = indexOf(terms[i]);
    }
    return res;                  
  }

}