How to find the differences between two xml files

When i was struggling with  comparing two xml files by writing lot of Code , i came to know about XMLUnit.
Take a look at this cool code ( copied from http://xmlunit.sourceforge.net/api/overview-summary.html)
XMLUnit provides extensions to the JUnit framework to allow assertions to be made about XML content.

Using XMLUnit

1. Create a subclass of XMLTestCasesomething like this:

   public class TestSomething extends XMLTestcase {
       // standard JUnit style constructor
       public TestSomething(String name) {
           super(name);
       }
       // standard JUnit style method
       public static TestSuite suite() {
           return new TestSuite(TestSomething.class);
       }
   }
   

2. Set the global JAXP settings in XMLUnitso that your chosen parser and transformer are used for the tests.
   Note:You can skip this bit if you use the default JAXP settings or you have an Ant task that uses-D JVM options to specify the JAXP settings.

   // set the JAXP factories to use the Xerces parser
       // - declare to throw Exception as if this fails then all the tests will
       // fail, and JUnit copes with these Exceptions for us
       public void setUp() throws Exception {
           XMLUnit.setControlParser(
               "org.apache.xerces.jaxp.DocumentBuilderFactoryImpl");
           // this next line is strictly not required - if no test parser is
           // explicitly specified then the same factory class will be used for
           // both test and control
           XMLUnit.setTestParser(
               "org.apache.xerces.jaxp.DocumentBuilderFactoryImpl");
   
           XMLUnit.setSAXParserFactory(
               "org.apache.xerces.jaxp.SAXParserFactoryImpl");
           XMLUnit.setTransformerFactory(
               "org.apache.xalan.processor.TransformerFactoryImpl");
       }
   

3. Add test methods to make your assertions: theXMLTestCase javadoc lists the available assertion methods and their usage, but here are some examples...

   public void testObjectAsXML() throws Exception {
           String expectedXML = "....";
           String objectAsXML = null;
           //...set up some object here and serialize its state into
           //our test String...
           assertXMLEqual(expectedXML, objectAsXML);
       }
   
       public void testTransformToFormatB() throws Exception {
           String expectedFormatB = "....";
           String formatA = "....";
           String transformXSLT = "....";
           Transform formatAToFormatB = new Transform(formatA, transformXSLT);
           assertXMLEqual(new Diff(expectedFormatB, formatAToFormatB), true);
       }
   
       public void testIsValidAfterTransform() throws Exception {
           String incomingMessage = "....";
           String toSourceSystemXSLT = "....";
           Transform transform = new Transform(incomingMessage, toSourceSystemXSLT);
           assertXMLValid(transform.getResultString());
       }
   
       public void testXpaths() throws Exception {
           String ukCustomerContactPhoneNos = "//customer[@country='UK']/contact/phone";
           String customerExtract1 = "....";
           String customerExtract2 = "....";
           assertXpathsNotEqual(ukCustomerContactPhoneNos, customerExtract1,
               ukCustomerContactPhoneNos, customerExtract2);
       }
   
       public void testXpathValues() throws Exception {
           String firstListItem = "/html/body/div[@id='myList']/h1/ol/li[1]";
           String secondListItem = "/html/body/div[@id='myList']/h1/ol/li[2]";
           String myHtmlPage = "....";
           assertXpathValuesNotEqual(firstListItem, secondListItem, myHtmlPage);
       }
   
       public void testSpecificXpath() throws Exception {
           String todaysTop10 = "count(//single[@topTen='true'])";
           String playlist = "....";
           assertXpathEvaluatesTo("10", todaysTop10, playlist);
   
       }