<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT music (artist*)>
<!ELEMENT artist (album+)>
<!ELEMENT album (#PCDATA)>
<!ATTLIST artist name CDATA #REQUIRED>

<?xml version="1.0" encoding="UTF-8"?>
<music>
    <artist name="Anderson, Laurie">
        <album>Big Science</album>
        <album>Strange Angels</album>
    </artist>
    <artist name="Fine Young Cannibals">
        <album>The Raw &amp; The Cooked</album>
        <album>The Raw &amp; The Cooked</album>
    </artist>
</music>

public void setParser() {
 
        XMLReader xmlReader = null;
        try {
 
            SAXParserFactory spfactory = SAXParserFactory.newInstance();
 
            spfactory.setValidating(true);
 
            SAXParser saxParser =
                    spfactory.newSAXParser();
 
            xmlReader = saxParser.getXMLReader();
 
            xmlReader.setEntityResolver(new EntityResolver() {
                @Override
                public InputSource resolveEntity(String publicId, String systemId)
                        throws SAXException, IOException {
                    return new InputSource("test.dtd");
                    //return new InputSource(new StringReader("<!ELEMENT music (artist*)>\n"
                    //        + "<!ELEMENT artist (album+)>\n"
                    //        + "<!ELEMENT album (#PCDATA)>\n"
                    //        + "<!ATTLIST artist name CDATA #REQUIRED>"));
                }
            });
            xmlReader.setContentHandler(this);
            xmlReader.setErrorHandler(this);
 
            InputSource source = new InputSource("test.xml");
            xmlReader.parse(source);
 
        } catch (SAXException | ParserConfigurationException | IOException ex) {
 
            ex.printStackTrace();
 
        } finally {
        }
 
    }

Ошибка: org.xml.sax.SAXParseException; systemId: file:///home/user/NetBeansProjects/arserTest/test.xml; lineNumber: 2; columnNumber: 8; Document root element "music", must match DOCTYPE root "null".
Ошибка: org.xml.sax.SAXParseException; systemId: file:///home/user/NetBeansProjects/arserTest/test.xml; lineNumber: 2; columnNumber: 8; Document is invalid: no grammar found.