XMLOutputFactory of = XMLOutputFactory.newInstance();
        XMLStreamWriter w = of.createXMLStreamWriter(new ByteArrayOutputStream());
        System.out.println(w);

The above code throws the following exception when run with JDK6.

Exception in thread "main" java.lang.UnsupportedOperationException
        at com.sun.xml.internal.stream.writers.XMLStreamWriterImpl.entrySet(XMLStreamWriterImpl.java:2126)
        at java.util.AbstractMap.toString(AbstractMap.java:478)
        at java.lang.String.valueOf(String.java:2827)
        at java.io.PrintStream.println(PrintStream.java:771)
        at WhichSjsxp.main(WhichSjsxp.java:21)