Lucene Highlighter TokenStream exception

I have a problem with Lucene Highlighter. I found some code on Stackoverflow and on other, but this code does not work in my program. This is a method where I try search and higlight words, but when I search something, program gives me exception.

Method:

private static void useIndex(String query, String field, String option)
            throws ParseException, CorruptIndexException, IOException, InvalidTokenOffsetsException {
        // StandardAnalyzer analyzer = new StandardAnalyzer();
        Query q = new QueryParser(field, analyzer).parse(query);

        int hitsPerPage = 5;

        IndexReader reader = DirectoryReader.open(index);
        IndexSearcher searcher = new IndexSearcher(reader);

        TopScoreDocCollector collector = TopScoreDocCollector.create(hitsPerPage);

        searcher.search(q, collector);

        ScoreDoc[] hits = collector.topDocs().scoreDocs;

        SimpleHTMLFormatter htmlFormatter = new SimpleHTMLFormatter();
        Highlighter highlighter = new Highlighter(htmlFormatter, new QueryScorer(q));

        // display results
        System.out.println("Found " + hits.length + " hits for " + query);
        for (int i = 0; i < hits.length; ++i) {
            int docId = hits[i].doc;
            Document d = searcher.doc(docId);
            String docURL = d.get("url");
            String docContent = d.get("content");

            TokenStream tokenStream = TokenSources.getAnyTokenStream(reader, docId, "content", analyzer);
            TextFragment[] frag = highlighter.getBestTextFragments(tokenStream, docContent, false, 4);

            String docFrag="";

            if ((frag[0] != null) && (frag[0].getScore() > 0)) {
                docFrag=frag[0].toString();
            }
            model.addRow(new Object[] { docURL, findSilimar(docId), docFrag });
        }
        reader.close();
    }

Exception:

    Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: org/apache/lucene/index/memory/MemoryIndex
Caused by: java.lang.ClassNotFoundException: org.apache.lucene.index.memory.MemoryIndex

I tried everything, but I don't know what is wrong.

P.S. Sorry for my English.

A NoClassDefFoundError means that class isn't in your classpath, so you should figure out what jar you need to add to get it. MemoryIndex is in: lucene-memory-x.x.x.jar

By the way, at a glance, it doesn't appear that this exception would be thrown in the code you've provided.