Empty Query - More Like This (Lucene)

Question

I'm new at Java and Lucene. I'm trying a simple MLT test, but I'm not getting any results.

import java.io.File;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.store.Directory;
import org.apache.lucene.util.Version;
import org.apache.lucene.index.DirectoryReader;
import java.io.IOException;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.queries.mlt.MoreLikeThis;
import org.apache.lucene.queryparser.classic.ParseException;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.SimpleFSDirectory;

public class HelloLucene {
  public static void main(String[] args) throws IOException, ParseException {
    StandardAnalyzer analyzer = new StandardAnalyzer(Version.LUCENE_40);

    String indexPath = "C:/Users/Name/Desktop/Lucene";
    Directory index = new SimpleFSDirectory(new File(indexPath)); 

    IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_40, analyzer);

    IndexWriter w = new IndexWriter(index, config);
    addDoc(w, "Lucene in Action", "193398817");
    addDoc(w, "Lucene for Dummies", "55320055Z");
    addDoc(w, "Managing Gigabytes", "55063554A");
    addDoc(w, "The Art of Computer Science", "9900333X");
    w.close();  

    IndexReader reader = DirectoryReader.open(index);
    System.out.println("Reader has " + reader.numDocs() + " docs on it.");

    MoreLikeThis mlt = new MoreLikeThis(reader);
    mlt.setMinTermFreq(1);
    mlt.setMinDocFreq(1);
    Query query = mlt.like(0); //doc ID

    IndexSearcher searcher = new IndexSearcher(reader);    
    TopDocs topDocs = searcher.search(query,5);

    System.out.println("Found " + topDocs.totalHits + " hits.");

    for (ScoreDoc scoreDoc : topDocs.scoreDocs) {
        Document doc = searcher.doc(scoreDoc.doc);
        System.out.println(scoreDoc.doc + ". " + doc.get("isbn") + "\t" + doc.get("title"));
    }    

    reader.close();

  }

  private static void addDoc(IndexWriter w, String title, String isbn) throws IOException {
    Document doc = new Document();
    doc.add(new TextField("title", title, Field.Store.YES));

    // use a string field for isbn because we don't want it tokenized
    doc.add(new StringField("isbn", isbn, Field.Store.YES));
    w.addDocument(doc);
  }
}

And this is what I get:

Reader has 4 docs on it.
Found 0 hits.

I tried using Luke to check the Doc's ID and there is nothing wrong apparently.
I even did some tests there, I dont know whats wrong :(
Did a lot of searching on the web, someone said something about the settings as MinTermFreq and MinDocFreq, I tried 1 and 0, but got nothing.

Does anyone have an idea?
Thanks in advance!

[SOLVED] Edited:

its working now!
I just had to add this:

mlt.setAnalyzer(analyzer);
mlt.setFieldNames(new String[] {"title"});

Answer 1

its working now! I just had to add this:

mlt.setAnalyzer(analyzer); mlt.setFieldNames(new String[] {"title"});