Indexing bigrams and trigrams in Lucene

[Venkateshprasanna]

I need to index bigrams and trigrams in a document. Here is an example:

Text:
This is a text document written by someone. Read this and post your comments

words that must be indexed:
text
document
written
someone
read
post
your
comments
text document
document written
post your
your comments
text document written
post your comments

So, I made changes to StandardAnalyzer.java and StandardTokenizer.jj to try
and achieve this.

I increased the LOOKAHEAD option value to 4:

options {
  LOOKAHEAD = 4;
  FORCE_LA_CHECK = true;
  .
  .
}


I made the following changes to StandardTokenizer.jj :

org.apache.lucene.analysis.Token next() throws IOException :
  :
  :
    {
      if (token.kind == EOF) {
        return null;
      }
      
      else if(token.kind == ALPHANUM) {
        
        Token nextToken = token.next;
        if(token.next.kind ==ALPHANUM) {
           return
           new org.apache.lucene.analysis.Token(token.image+" "+nextToken.image,
                                        token.beginColumn,nextToken.endColumn,
                                        tokenImage[token.kind]);
        }
      }
        
      else {
        return
          new org.apache.lucene.analysis.Token(token.image,
                                        token.beginColumn,token.endColumn,
                                        tokenImage[token.kind]);
      }
    }


That is, I am using token.next to get info about the next token. But it is
returning null. What is the reason and is there a better way of doing this?


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