在Lucene中添加BM25评分

Question

我是Lucene的新人。我使用Lucene-3.6.0.jar在java中使用Lucene。我遵循了http://www.tutorialspoint.com/lucene/上的教程。我的基本代码如下：

public class LuceneTester {
String indexDir = "Data/Indexdir";
String dataDir = "Data/Datadir";
Indexer indexer;
Searcher searcher;

public static void test() {
    LuceneTester tester;
    try {
        tester = new LuceneTester();
        tester.createIndex();
        tester.search("malformed");
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ParseException e) {
        e.printStackTrace();
    }
}

private void createIndex() throws IOException {
    indexer = new Indexer(indexDir);
    int numIndexed;
    long startTime = System.currentTimeMillis();
    numIndexed = indexer.createIndex(dataDir, new TextFileFilter());
    long endTime = System.currentTimeMillis();
    indexer.close();
    System.out.println(numIndexed + " File indexed, time taken: "
            + (endTime - startTime) + " ms");
}

private void search(String searchQuery) throws IOException, ParseException {
    searcher = new Searcher(indexDir);
    long startTime = System.currentTimeMillis();
    Term term = new Term(LuceneConstants.CONTENTS, searchQuery);
    Query query = new FuzzyQuery(term);
    System.out.println("Query: " + query.toString());
    TopDocs hits = searcher.search(query, Sort.RELEVANCE);
    long endTime = System.currentTimeMillis();
    System.out.println(hits.totalHits + " documents found. Time :"
            + (endTime - startTime));
    for (ScoreDoc scoreDoc : hits.scoreDocs) {
        Document doc = searcher.getDocument(scoreDoc);
        System.out.println("File: " + doc.get(LuceneConstants.FILE_PATH));
    }
    searcher.close();
}

现在，我想使用BM25相似度而不是默认的评分技术。该怎么做呢？