Java HTML/XML - 如何使用DOM解析器解析XML文档，每个标记有多个元素

import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;

public class Main {

  public static void main(String[] args) throws Exception {
    XPathFactory xpf = XPathFactory.newInstance();
    XPath xPath = xpf.newXPath();
    XPathExpression schoolNameExpression = xPath.compile("SchoolName");
    XPathExpression classNameExpression = xPath
        .compile("Classes/Class/ClassName");

    InputSource inputSource = new InputSource("input.xml");
    NodeList schoolNodes = (NodeList) xPath.evaluate("/Data/Schools/School",
        inputSource, XPathConstants.NODESET);
    for (int x = 0; x < schoolNodes.getLength(); x++) {
      Node schoolElement = schoolNodes.item(x);
      System.out.println(schoolNameExpression.evaluate(schoolElement,
          XPathConstants.STRING));
      NodeList classNames = (NodeList) classNameExpression.evaluate(
          schoolElement, XPathConstants.NODESET);
      for (int y = 0; y < classNames.getLength(); y++) {
        System.out.println(classNames.item(y).getTextContent());
      }
    }
  }
}