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Lucene example source code file (TestTopDocsCollector.java)

This example Lucene source code file (TestTopDocsCollector.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

document, exception, exception, indexreader, io, ioexception, ioexception, mytopsdoccollector, override, override, randomindexwriter, scoredoc, topdocs, topdocscollector, topdocscollector

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

import java.io.IOException;

import org.apache.lucene.document.Document;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.RandomIndexWriter;
import org.apache.lucene.store.Directory;
import org.apache.lucene.util.LuceneTestCase;

public class TestTopDocsCollector extends LuceneTestCase {

  private static final class MyTopsDocCollector extends TopDocsCollector<ScoreDoc> {

    private int idx = 0;
    private int base = 0;
    public MyTopsDocCollector(int size) {
      super(new HitQueue(size, false));
    protected TopDocs newTopDocs(ScoreDoc[] results, int start) {
      if (results == null) {
        return EMPTY_TOPDOCS;
      float maxScore = Float.NaN;
      if (start == 0) {
        maxScore = results[0].score;
      } else {
        for (int i = pq.size(); i > 1; i--) { pq.pop(); }
        maxScore = pq.pop().score;
      return new TopDocs(totalHits, results, maxScore);
    public void collect(int doc) throws IOException {
      pq.insertWithOverflow(new ScoreDoc(doc + base, scores[idx++]));

    public void setNextReader(IndexReader reader, int docBase)
        throws IOException {
      base = docBase;

    public void setScorer(Scorer scorer) throws IOException {
      // Don't do anything. Assign scores in random
    public boolean acceptsDocsOutOfOrder() {
      return true;


  // Scores array to be used by MyTopDocsCollector. If it is changed, MAX_SCORE
  // must also change.
  private static final float[] scores = new float[] {
    0.7767749f, 1.7839992f, 8.9925785f, 7.9608946f, 0.07948637f, 2.6356435f, 
    7.4950366f, 7.1490803f, 8.108544f, 4.961808f, 2.2423935f, 7.285586f, 4.6699767f,
    2.9655676f, 6.953706f, 5.383931f, 6.9916306f, 8.365894f, 7.888485f, 8.723962f,
    3.1796896f, 0.39971232f, 1.3077754f, 6.8489285f, 9.17561f, 5.060466f, 7.9793315f,
    8.601509f, 4.1858315f, 0.28146625f
  private static final float MAX_SCORE = 9.17561f;
  private Directory dir;
  private IndexReader reader;

  private TopDocsCollector<ScoreDoc> doSearch(int numResults) throws IOException {
    Query q = new MatchAllDocsQuery();
    IndexSearcher searcher = newSearcher(reader);
    TopDocsCollector<ScoreDoc> tdc = new MyTopsDocCollector(numResults);
    searcher.search(q, tdc);
    return tdc;
  public void setUp() throws Exception {
    // populate an index with 30 documents, this should be enough for the test.
    // The documents have no content - the test uses MatchAllDocsQuery().
    dir = newDirectory();
    RandomIndexWriter writer = new RandomIndexWriter(random, dir);
    for (int i = 0; i < 30; i++) {
      writer.addDocument(new Document());
    reader = writer.getReader();
  public void tearDown() throws Exception {
    dir = null;
  public void testInvalidArguments() throws Exception {
    int numResults = 5;
    TopDocsCollector<ScoreDoc> tdc = doSearch(numResults);
    // start < 0
    assertEquals(0, tdc.topDocs(-1).scoreDocs.length);
    // start > pq.size()
    assertEquals(0, tdc.topDocs(numResults + 1).scoreDocs.length);
    // start == pq.size()
    assertEquals(0, tdc.topDocs(numResults).scoreDocs.length);
    // howMany < 0
    assertEquals(0, tdc.topDocs(0, -1).scoreDocs.length);
    // howMany == 0
    assertEquals(0, tdc.topDocs(0, 0).scoreDocs.length);
  public void testZeroResults() throws Exception {
    TopDocsCollector<ScoreDoc> tdc = new MyTopsDocCollector(5);
    assertEquals(0, tdc.topDocs(0, 1).scoreDocs.length);
  public void testFirstResultsPage() throws Exception {
    TopDocsCollector<ScoreDoc> tdc = doSearch(15);
    assertEquals(10, tdc.topDocs(0, 10).scoreDocs.length);
  public void testSecondResultsPages() throws Exception {
    TopDocsCollector<ScoreDoc> tdc = doSearch(15);
    // ask for more results than are available
    assertEquals(5, tdc.topDocs(10, 10).scoreDocs.length);
    // ask for 5 results (exactly what there should be
    tdc = doSearch(15);
    assertEquals(5, tdc.topDocs(10, 5).scoreDocs.length);
    // ask for less results than there are
    tdc = doSearch(15);
    assertEquals(4, tdc.topDocs(10, 4).scoreDocs.length);
  public void testGetAllResults() throws Exception {
    TopDocsCollector<ScoreDoc> tdc = doSearch(15);
    assertEquals(15, tdc.topDocs().scoreDocs.length);
  public void testGetResultsFromStart() throws Exception {
    TopDocsCollector<ScoreDoc> tdc = doSearch(15);
    // should bring all results
    assertEquals(15, tdc.topDocs(0).scoreDocs.length);
    tdc = doSearch(15);
    // get the last 5 only.
    assertEquals(5, tdc.topDocs(10).scoreDocs.length);
  public void testMaxScore() throws Exception {
    // ask for all results
    TopDocsCollector<ScoreDoc> tdc = doSearch(15);
    TopDocs td = tdc.topDocs();
    assertEquals(MAX_SCORE, td.getMaxScore(), 0f);
    // ask for 5 last results
    tdc = doSearch(15);
    td = tdc.topDocs(10);
    assertEquals(MAX_SCORE, td.getMaxScore(), 0f);
  // This does not test the PQ's correctness, but whether topDocs()
  // implementations return the results in decreasing score order.
  public void testResultsOrder() throws Exception {
    TopDocsCollector<ScoreDoc> tdc = doSearch(15);
    ScoreDoc[] sd = tdc.topDocs().scoreDocs;
    assertEquals(MAX_SCORE, sd[0].score, 0f);
    for (int i = 1; i < sd.length; i++) {
      assertTrue(sd[i - 1].score >= sd[i].score);

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