LengthFilter.java

package org.apache.lucene.analysis;

import java.io.IOException;
 
import org.apache.lucene.analysis.tokenattributes.TermAttribute;
 
/**
 * Removes words that are too long or too short from the stream.
 */
public final class LengthFilter extends TokenFilter {
 
  final int min;
  final int max;
  
  private TermAttribute termAtt;
 
  /**
   * Build a filter that removes words that are too long or too
   * short from the text.
   */
  public LengthFilter(TokenStream in, int min, int max)
  {
    super(in);
    this.min = min;
    this.max = max;
    // input.incrementToken()을 하면 termAtt도 그에 따라 변한다.
    termAtt = addAttribute(TermAttribute.class);
  }
  
  /**
   * Returns the next input Token whose term() is the right len
   */
  @Override
  public final boolean incrementToken() throws IOException {
    while (input.incrementToken()) {
      int len = termAtt.termLength();
      // term 길이가 적합할 때 까지 incrementToken()을 실행한다.
      if (len >= min && len <= max) {
          return true;
      }
      // note: else we ignore it but should we index each part of it?
    }
    // reached EOS -- return false
    return false;
  }
}