lucene9 给个demo

好的，下面是一个简单的 Lucene9 的示例代码，包括创建索引和搜索：

import java.io.IOException;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.Term;
import org.apache.lucene.queryparser.classic.ParseException;
import org.apache.lucene.queryparser.classic.QueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.store.RAMDirectory;
import java.nio.file.Paths;

public class LuceneDemo {

    public static void main(String[] args) throws IOException, ParseException {

        // 创建索引
        Directory directory = FSDirectory.open(Paths.get("index"));
        IndexWriterConfig config = new IndexWriterConfig(new StandardAnalyzer());
        IndexWriter writer = new IndexWriter(directory, config);

        Document doc1 = new Document();
        doc1.add(new TextField("content", "Lucene is a full-text search engine library in Java", Field.Store.YES));
        writer.addDocument(doc1);

        Document doc2 = new Document();
        doc2.add(new TextField("content", "Lucene is used to build search applications", Field.Store.YES));
        writer.addDocument(doc2);

        writer.close();

        // 搜索
        Directory directory2 = FSDirectory.open(Paths.get("index"));
        IndexSearcher searcher = new IndexSearcher(directory2);

        // TermQuery
        Query termQuery = new TermQuery(new Term("content", "search"));
        TopDocs topDocs = searcher.search(termQuery, 10);
        for (ScoreDoc scoreDoc : topDocs.scoreDocs) {
            Document doc = searcher.doc(scoreDoc.doc);
            System.out.println(doc.get("content") + " score: " + scoreDoc.score);
        }

        // QueryParser
        QueryParser parser = new QueryParser("content", new StandardAnalyzer());
        Query query = parser.parse("Lucene search");
        TopDocs topDocs2 = searcher.search(query, 10);
        for (ScoreDoc scoreDoc : topDocs2.scoreDocs) {
            Document doc = searcher.doc(scoreDoc.doc);
            System.out.println(doc.get("content") + " score: " + scoreDoc.score);
        }

        searcher.getIndexReader().close();
        directory2.close();
    }
}

以上代码创建了一个包含两条文档的索引，然后使用 TermQuery 和 QueryParser 分别进行了搜索，并打印出了搜索结果。