title: How to get frequently occurring phrases with Lucene
body: <p>I would like to get some frequently occurring phrases with Lucene. I am getting some information from TXT files, and I am losing a lot of context for not having information for phrases e.g. "information retrieval" is indexed as two separate words.</p>
  
  <p>What is the way to get the phrases like this? I can not find anything useful on internet, all the advices, links, hints especially examples are appreciated!</p>
  
  <p><strong>EDIT:</strong> I store my documents just by title and content:</p>
  
  <pre><code> Document doc = new Document();
   doc.add(new Field("name", f.getName(), Field.Store.YES, Field.Index.NOT_ANALYZED));
   doc.add(new Field("text", fReader, Field.TermVector.WITH_POSITIONS_OFFSETS));
  </code></pre>
  
  <p>because for what I am doing the most important is the content of the file. Titles are too often not descriptive at all (e.g., I have many PDF academic papers whose titles are codes or numbers).</p>
  
  <p>I desperately need to index top occurring phrases from text contents, just now I see how much this simple "bag of words" approach is not efficient.</p>