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Lucene example source code file (SentenceTokenizer.java)

This example Lucene source code file (SentenceTokenizer.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

chartermattribute, io, ioexception, ioexception, offsetattribute, override, override, punction, reader, reader, sentencetokenizer, sentencetokenizer, stringbuilder, tokenizer, typeattribute

The Lucene SentenceTokenizer.java source code

/**
 * 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.
 */

package org.apache.lucene.analysis.cn.smart;

import java.io.IOException;
import java.io.Reader;

import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
import org.apache.lucene.util.AttributeSource;

/**
 * Tokenizes input text into sentences.
 * <p>
 * The output tokens can then be broken into words with {@link WordTokenFilter}
 * </p>
 * @lucene.experimental
 */
public final class SentenceTokenizer extends Tokenizer {

  /**
   * End of sentence punctuation: 。,!?;,!?;
   */
  private final static String PUNCTION = "。,!?;,!?;";

  private final StringBuilder buffer = new StringBuilder();

  private int tokenStart = 0, tokenEnd = 0;
  
  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
  private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
  private final TypeAttribute typeAtt = addAttribute(TypeAttribute.class);

  public SentenceTokenizer(Reader reader) {
    super(reader);
  }

  public SentenceTokenizer(AttributeSource source, Reader reader) {
    super(source, reader);
  }

  public SentenceTokenizer(AttributeFactory factory, Reader reader) {
    super(factory, reader);
  }
  
  @Override
  public boolean incrementToken() throws IOException {
    clearAttributes();
    buffer.setLength(0);
    int ci;
    char ch, pch;
    boolean atBegin = true;
    tokenStart = tokenEnd;
    ci = input.read();
    ch = (char) ci;

    while (true) {
      if (ci == -1) {
        break;
      } else if (PUNCTION.indexOf(ch) != -1) {
        // End of a sentence
        buffer.append(ch);
        tokenEnd++;
        break;
      } else if (atBegin && Utility.SPACES.indexOf(ch) != -1) {
        tokenStart++;
        tokenEnd++;
        ci = input.read();
        ch = (char) ci;
      } else {
        buffer.append(ch);
        atBegin = false;
        tokenEnd++;
        pch = ch;
        ci = input.read();
        ch = (char) ci;
        // Two spaces, such as CR, LF
        if (Utility.SPACES.indexOf(ch) != -1
            && Utility.SPACES.indexOf(pch) != -1) {
          // buffer.append(ch);
          tokenEnd++;
          break;
        }
      }
    }
    if (buffer.length() == 0)
      return false;
    else {
      termAtt.setEmpty().append(buffer);
      offsetAtt.setOffset(correctOffset(tokenStart), correctOffset(tokenEnd));
      typeAtt.setType("sentence");
      return true;
    }
  }

  @Override
  public void reset() throws IOException {
    super.reset();
    tokenStart = tokenEnd = 0;
  }

  @Override
  public void reset(Reader input) throws IOException {
    super.reset(input);
    reset();
  }

  @Override
  public void end() throws IOException {
    // set final offset
    final int finalOffset = correctOffset(tokenEnd);
    offsetAtt.setOffset(finalOffset, finalOffset);
  }
}

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