Lucene example source code file (NGramTokenFilterTest.java)

This example Lucene source code file (NGramTokenFilterTest.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

basetokenstreamtestcase, exception, exception, illegalargumentexception, io, mocktokenizer, ngramtokenfilter, ngramtokenfilter, ngramtokenfiltertest, override, string, string, stringreader, stringreader, whitespacetokenizer

The Lucene NGramTokenFilterTest.java source code

package org.apache.lucene.analysis.ngram;

/**
 * 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 org.apache.lucene.analysis.MockTokenizer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.WhitespaceTokenizer;
import org.apache.lucene.analysis.BaseTokenStreamTestCase;

import java.io.StringReader;

/**
 * Tests {@link NGramTokenFilter} for correctness.
 */
public class NGramTokenFilterTest extends BaseTokenStreamTestCase {
    private TokenStream input;
    
    @Override
    public void setUp() throws Exception {
        super.setUp();
        input = new MockTokenizer(new StringReader("abcde"), MockTokenizer.WHITESPACE, false);
    }

    public void testInvalidInput() throws Exception {
        boolean gotException = false;
        try {        
            new NGramTokenFilter(input, 2, 1);
        } catch (IllegalArgumentException e) {
            gotException = true;
        }
        assertTrue(gotException);
    }

    public void testInvalidInput2() throws Exception {
        boolean gotException = false;
        try {        
            new NGramTokenFilter(input, 0, 1);
        } catch (IllegalArgumentException e) {
            gotException = true;
        }
        assertTrue(gotException);
    }

    public void testUnigrams() throws Exception {
      NGramTokenFilter filter = new NGramTokenFilter(input, 1, 1);
      assertTokenStreamContents(filter, new String[]{"a","b","c","d","e"}, new int[]{0,1,2,3,4}, new int[]{1,2,3,4,5});
    }

    public void testBigrams() throws Exception {
      NGramTokenFilter filter = new NGramTokenFilter(input, 2, 2);
      assertTokenStreamContents(filter, new String[]{"ab","bc","cd","de"}, new int[]{0,1,2,3}, new int[]{2,3,4,5});
    }

    public void testNgrams() throws Exception {
      NGramTokenFilter filter = new NGramTokenFilter(input, 1, 3);
      assertTokenStreamContents(filter,
        new String[]{"a","b","c","d","e", "ab","bc","cd","de", "abc","bcd","cde"}, 
        new int[]{0,1,2,3,4, 0,1,2,3, 0,1,2},
        new int[]{1,2,3,4,5, 2,3,4,5, 3,4,5}
      );
    }

    public void testOversizedNgrams() throws Exception {
      NGramTokenFilter filter = new NGramTokenFilter(input, 6, 7);
      assertTokenStreamContents(filter, new String[0], new int[0], new int[0]);
    }
    
    public void testSmallTokenInStream() throws Exception {
      input = new MockTokenizer(new StringReader("abc de fgh"), MockTokenizer.WHITESPACE, false);
      NGramTokenFilter filter = new NGramTokenFilter(input, 3, 3);
      assertTokenStreamContents(filter, new String[]{"abc","fgh"}, new int[]{0,7}, new int[]{3,10});
    }
    
    public void testReset() throws Exception {
      WhitespaceTokenizer tokenizer = new WhitespaceTokenizer(TEST_VERSION_CURRENT, new StringReader("abcde"));
      NGramTokenFilter filter = new NGramTokenFilter(tokenizer, 1, 1);
      assertTokenStreamContents(filter, new String[]{"a","b","c","d","e"}, new int[]{0,1,2,3,4}, new int[]{1,2,3,4,5});
      tokenizer.reset(new StringReader("abcde"));
      assertTokenStreamContents(filter, new String[]{"a","b","c","d","e"}, new int[]{0,1,2,3,4}, new int[]{1,2,3,4,5});
    }
}