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Lucene example source code file (TestStopFilter.java)

This example Lucene source code file (TestStopFilter.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, io, ioexception, mocktokenizer, mocktokenizer, now, set, stopfilter, stopfilter, string, string, stringreader, stringreader, the, time, util

The Lucene TestStopFilter.java source code

package org.apache.lucene.analysis;

/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed 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 org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.util.English;
import org.apache.lucene.util.Version;

import java.io.IOException;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Set;
import java.util.HashSet;

import org.apache.lucene.analysis.BaseTokenStreamTestCase;
import org.apache.lucene.analysis.MockTokenizer;
import org.apache.lucene.analysis.TokenStream;

public class TestStopFilter extends BaseTokenStreamTestCase {
  
  // other StopFilter functionality is already tested by TestStopAnalyzer

  public void testExactCase() throws IOException {
    StringReader reader = new StringReader("Now is The Time");
    Set<String> stopWords = new HashSet(Arrays.asList("is", "the", "Time"));
    TokenStream stream = new StopFilter(TEST_VERSION_CURRENT, new MockTokenizer(reader, MockTokenizer.WHITESPACE, false), stopWords, false);
    assertTokenStreamContents(stream, new String[] { "Now", "The" });
  }

  public void testIgnoreCase() throws IOException {
    StringReader reader = new StringReader("Now is The Time");
    Set<Object> stopWords = new HashSet(Arrays.asList( "is", "the", "Time" ));
    TokenStream stream = new StopFilter(TEST_VERSION_CURRENT, new MockTokenizer(reader, MockTokenizer.WHITESPACE, false), stopWords, true);
    assertTokenStreamContents(stream, new String[] { "Now" });
  }

  public void testStopFilt() throws IOException {
    StringReader reader = new StringReader("Now is The Time");
    String[] stopWords = new String[] { "is", "the", "Time" };
    Set<Object> stopSet = StopFilter.makeStopSet(TEST_VERSION_CURRENT, stopWords);
    TokenStream stream = new StopFilter(TEST_VERSION_CURRENT, new MockTokenizer(reader, MockTokenizer.WHITESPACE, false), stopSet);
    assertTokenStreamContents(stream, new String[] { "Now", "The" });
  }

  /**
   * Test Position increments applied by StopFilter with and without enabling this option.
   */
  public void testStopPositons() throws IOException {
    StringBuilder sb = new StringBuilder();
    ArrayList<String> a = new ArrayList();
    for (int i=0; i<20; i++) {
      String w = English.intToEnglish(i).trim();
      sb.append(w).append(" ");
      if (i%3 != 0) a.add(w);
    }
    log(sb.toString());
    String stopWords[] = a.toArray(new String[0]);
    for (int i=0; i<a.size(); i++) log("Stop: "+stopWords[i]);
    Set<Object> stopSet = StopFilter.makeStopSet(TEST_VERSION_CURRENT, stopWords);
    // with increments
    StringReader reader = new StringReader(sb.toString());
    StopFilter stpf = new StopFilter(Version.LUCENE_24, new MockTokenizer(reader, MockTokenizer.WHITESPACE, false), stopSet);
    doTestStopPositons(stpf,true);
    // without increments
    reader = new StringReader(sb.toString());
    stpf = new StopFilter(TEST_VERSION_CURRENT, new MockTokenizer(reader, MockTokenizer.WHITESPACE, false), stopSet);
    doTestStopPositons(stpf,false);
    // with increments, concatenating two stop filters
    ArrayList<String> a0 = new ArrayList();
    ArrayList<String> a1 = new ArrayList();
    for (int i=0; i<a.size(); i++) {
      if (i%2==0) { 
        a0.add(a.get(i));
      } else {
        a1.add(a.get(i));
      }
    }
    String stopWords0[] =  a0.toArray(new String[0]);
    for (int i=0; i<a0.size(); i++) log("Stop0: "+stopWords0[i]);
    String stopWords1[] =  a1.toArray(new String[0]);
    for (int i=0; i<a1.size(); i++) log("Stop1: "+stopWords1[i]);
    Set<Object> stopSet0 = StopFilter.makeStopSet(TEST_VERSION_CURRENT, stopWords0);
    Set<Object> stopSet1 = StopFilter.makeStopSet(TEST_VERSION_CURRENT, stopWords1);
    reader = new StringReader(sb.toString());
    StopFilter stpf0 = new StopFilter(TEST_VERSION_CURRENT, new MockTokenizer(reader, MockTokenizer.WHITESPACE, false), stopSet0); // first part of the set
    stpf0.setEnablePositionIncrements(true);
    StopFilter stpf01 = new StopFilter(TEST_VERSION_CURRENT, stpf0, stopSet1); // two stop filters concatenated!
    doTestStopPositons(stpf01,true);
  }
  
  private void doTestStopPositons(StopFilter stpf, boolean enableIcrements) throws IOException {
    log("---> test with enable-increments-"+(enableIcrements?"enabled":"disabled"));
    stpf.setEnablePositionIncrements(enableIcrements);
    CharTermAttribute termAtt = stpf.getAttribute(CharTermAttribute.class);
    PositionIncrementAttribute posIncrAtt = stpf.getAttribute(PositionIncrementAttribute.class);
    stpf.reset();
    for (int i=0; i<20; i+=3) {
      assertTrue(stpf.incrementToken());
      log("Token "+i+": "+stpf);
      String w = English.intToEnglish(i).trim();
      assertEquals("expecting token "+i+" to be "+w,w,termAtt.toString());
      assertEquals("all but first token must have position increment of 3",enableIcrements?(i==0?1:3):1,posIncrAtt.getPositionIncrement());
    }
    assertFalse(stpf.incrementToken());
    stpf.end();
    stpf.close();
  }
  
  // print debug info depending on VERBOSE
  private static void log(String s) {
    if (VERBOSE) {
      System.out.println(s);
    }
  }
}

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