Java HTML / XML How to - Compare structure of two XML files

Question

We would like to know how to compare structure of two XML files.
Answer

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.security.MessageDigest;
/* w  w  w.  ja  v  a 2 s.c om*/
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.events.XMLEvent;

public class Main {

  public static void main(String[] args) throws Exception {
    FileInputStream in1 = new FileInputStream(new File("file1.xml"));
    FileInputStream in2 = new FileInputStream(new File("file2.xml"));

    System.out.println(digest(in1));
    System.out.println(digest(in2));
  }

  public static String digest(InputStream in) throws Exception {
    MessageDigest messageDigest = null;
    XMLInputFactory inputFactory = XMLInputFactory.newFactory();
    messageDigest = MessageDigest.getInstance("MD5");
    XMLEventReader eventReader = inputFactory.createXMLEventReader(in);
    while (eventReader.hasNext()) {
      XMLEvent event = eventReader.nextEvent();

      if (event.isStartElement()) {
        messageDigest.update(event.asStartElement().getName().toString()
            .getBytes());
      } else if (event.isEndElement()) {
        messageDigest.update(event.asEndElement().getName().toString()
            .getBytes());
      }
    }
    StringBuffer result = new StringBuffer();
    byte[] digest = messageDigest.digest();
    for (byte b : digest){
      result.append(Integer.toString((b & 0xff) + 0x100, 16).substring(1));
    }
    return result.toString();
  }
}