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Lucene example source code file (TestMaxTermFrequency.java)

This example Lucene source code file (TestMaxTermFrequency.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, arraylist, document, document, exception, exception, indexreader, indexwriterconfig, lucenetestcase, mockanalyzer, override, override, randomindexwriter, testsimilarity, util

The Lucene TestMaxTermFrequency.java source code

package org.apache.lucene.index;

/**
 * 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.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import org.apache.lucene.analysis.MockAnalyzer;
import org.apache.lucene.analysis.MockTokenizer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.search.DefaultSimilarity;
import org.apache.lucene.store.Directory;
import org.apache.lucene.util.LuceneTestCase;
import org.apache.lucene.util._TestUtil;

/**
 * Tests the maxTermFrequency statistic in FieldInvertState
 */
public class TestMaxTermFrequency extends LuceneTestCase { 
  Directory dir;
  IndexReader reader;
  /* expected maxTermFrequency values for our documents */
  ArrayList<Integer> expected = new ArrayList();
  
  @Override
  public void setUp() throws Exception {
    super.setUp();
    dir = newDirectory();
    IndexWriterConfig config = newIndexWriterConfig(TEST_VERSION_CURRENT, 
               new MockAnalyzer(random, MockTokenizer.SIMPLE, true)).setMergePolicy(newLogMergePolicy());
    config.setSimilarity(new TestSimilarity());
    RandomIndexWriter writer = new RandomIndexWriter(random, dir, config);
    Document doc = new Document();
    Field foo = newField("foo", "", Field.Store.NO, Field.Index.ANALYZED);
    doc.add(foo);
    for (int i = 0; i < 100; i++) {
      foo.setValue(addValue());
      writer.addDocument(doc);
    }
    reader = writer.getReader();
    writer.close();
  }
  
  @Override
  public void tearDown() throws Exception {
    reader.close();
    dir.close();
    super.tearDown();
  }
  
  public void test() throws Exception {
    byte fooNorms[] = reader.norms("foo");
    for (int i = 0; i < reader.maxDoc(); i++)
      assertEquals(expected.get(i).intValue(), fooNorms[i] & 0xff);
  }

  /**
   * Makes a bunch of single-char tokens (the max freq will at most be 255).
   * shuffles them around, and returns the whole list with Arrays.toString().
   * This works fine because we use lettertokenizer.
   * puts the max-frequency term into expected, to be checked against the norm.
   */
  private String addValue() {
    List<String> terms = new ArrayList();
    int maxCeiling = _TestUtil.nextInt(random, 0, 255);
    int max = 0;
    for (char ch = 'a'; ch <= 'z'; ch++) {
      int num = _TestUtil.nextInt(random, 0, maxCeiling);
      for (int i = 0; i < num; i++)
        terms.add(Character.toString(ch));
      max = Math.max(max, num);
    }
    expected.add(max);
    Collections.shuffle(terms, random);
    return Arrays.toString(terms.toArray(new String[terms.size()]));
  }
  
  /**
   * Simple similarity that encodes maxTermFrequency directly as a byte
   */
  class TestSimilarity extends DefaultSimilarity {

    @Override
    public byte encodeNormValue(float f) {
      return (byte) f;
    }
    
    @Override
    public float decodeNormValue(byte b) {
      return (float) b;
    }

    @Override
    public float computeNorm(String field, FieldInvertState state) {
      return (float) state.getMaxTermFrequency();
    }
  }
}

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