How to validate XML against DTD

[Ekaterina Galkina]

Hello,
I'm trying to validate XML against external XSD and DTD and using an example from here http://faq.javaranch.com/java/HowToValidateXmlAgainstAnySchema
With XSD it's ok, but after I changed red lines in the following way:

factory.setAttribute(
				"http://java.sun.com/xml/jaxp/properties/schemaLanguage",
				"http://www.w3.org/TR/REC-xml");
factory.setAttribute(
				"http://java.sun.com/xml/jaxp/properties/schemaSource",
				"file.dtd");

I get an exception
java.lang.IllegalArgumentException: jaxp-order-not-supported: Property 'http://java.sun.com/xml/jaxp/properties/schemaLanguage' must be set before setting property 'http://java.sun.com/xml/jaxp/properties/schemaSource'

Could anyone explain me what does it mean? Thanks