如何在xml文件中写入并保存？

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;

public class WriteXML {
    public static void main(String[] args) {
        try {
            // 创建XML文档对象
            DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
            Document doc = docBuilder.newDocument();

            // 创建根元素
            Element rootElement = doc.createElement("books");
            doc.appendChild(rootElement);

            // 创建子元素
            Element bookElement = doc.createElement("book");
            rootElement.appendChild(bookElement);

            // 添加属性
            bookElement.setAttribute("id", "1");

            // 添加文本内容
            Element titleElement = doc.createElement("title");
            titleElement.appendChild(doc.createTextNode("Harry Potter"));
            bookElement.appendChild(titleElement);

            // 保存XML文件
            TransformerFactory transformerFactory = TransformerFactory.newInstance();
            Transformer transformer = transformerFactory.newTransformer();
            transformer.setOutputProperty(OutputKeys.INDENT, "yes"); // 缩进格式化输出
            DOMSource source = new DOMSource(doc);
            StreamResult result = new StreamResult(new File("books.xml"));
            transformer.transform(source, result);

            System.out.println("XML文件保存成功！");
        } catch (ParserConfigurationException | TransformerConfigurationException e) {
            e.printStackTrace();
        } catch (TransformerException e) {
            e.printStackTrace();
        }
    }
}