(DocumentBuilder).parse return null under jdk 1.5.0

Question

I would like to understand why the following code return a correct Document instance if it running under jdk 1.4.2 and instead return null if it running under jdk 1.5.0.
Thanks!
F.
import java.io.IOException;
import java.io.StringReader;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
String test = "<root>" + "" + "</root>";
StringReader sreader = new StringReader (test);
InputSource is = new InputSource(sreader);
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder;
builder = factory.newDocumentBuilder();
Document doc =  builder.parse(is);
System.out.println("Document is: " + doc);

Answer 1

Because you're using the toString() method to display the Document. It works differently in Java 5 than it did in Java 1.4. This is perfectly okay because the DOM specification doesn't say anything about what the toString() method should return. If you relied on that for anything other than debugging then you were relying on an undocumented feature. Shouldn't do that.