Exact Phrase search using Lucene?

Try a PhraseQuery instead:

PhraseQuery query = new PhraseQuery();
String[] words = sentence.split(" ");
for (String word : words) {
    query.add(new Term("contents", word));
}
booleanQuery.add(query, BooleanClause.Occur.MUST);

Edit: I think you have a different problem. What other parts are there to your booleanQuery? Here’s a full working example of searching for a phrase:

public class LucenePhraseQuery {
    public static void main(String[] args) throws Exception {
        // setup Lucene to use an in-memory index
        Directory directory = new RAMDirectory();
        Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_30);
        MaxFieldLength mlf = MaxFieldLength.UNLIMITED;
        IndexWriter writer = new IndexWriter(directory, analyzer, true, mlf);

        // index a few documents
        writer.addDocument(createDocument("1", "foo bar baz"));
        writer.addDocument(createDocument("2", "red green blue"));
        writer.addDocument(createDocument("3", "test foo bar test"));
        writer.close();

        // search for documents that have "foo bar" in them
        String sentence = "foo bar";
        IndexSearcher searcher = new IndexSearcher(directory);
        PhraseQuery query = new PhraseQuery();
        String[] words = sentence.split(" ");
        for (String word : words) {
            query.add(new Term("contents", word));
        }

        // display search results
        TopDocs topDocs = searcher.search(query, 10);
        for (ScoreDoc scoreDoc : topDocs.scoreDocs) {
            Document doc = searcher.doc(scoreDoc.doc);
            System.out.println(doc);
        }
    }

    private static Document createDocument(String id, String content) {
        Document doc = new Document();
        doc.add(new Field("id", id, Store.YES, Index.NOT_ANALYZED));
        doc.add(new Field("contents", content, Store.YES, Index.ANALYZED,
                Field.TermVector.WITH_POSITIONS_OFFSETS));
        return doc;
    }
}