如何读取XML文件？

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;

// 读取XML文件
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse("file.xml");

// 获取根节点
Node root = doc.getDocumentElement();

// 遍历子节点
NodeList nodeList = root.getChildNodes();
for (int i = 0; i < nodeList.getLength(); i++) {
    Node node = nodeList.item(i);
    if (node.getNodeType() == Node.ELEMENT_NODE) {
        // 处理子节点
        // ...
    }
}

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

// 读取XML文件
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();

// 创建解析处理器
DefaultHandler handler = new DefaultHandler() {
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        // 处理元素开始标签
        // ...
    }

    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        // 处理元素内容
        // ...
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        // 处理元素结束标签
        // ...
    }
};

// 解析XML文件
parser.parse("file.xml", handler);

import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

// 读取XML文件
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();
Document doc = builder.parse("file.xml");

// 执行XPath查询
String expression = "/root/element";
NodeList nodeList = (NodeList) xpath.evaluate(expression, doc, XPathConstants.NODESET);

// 遍历查询结果
for (int i = 0; i < nodeList.getLength(); i++) {
    Node node = nodeList.item(i);
    // 处理查询结果节点
    // ...
}