Validating XML with an external DTD

Hello,

I need help validating an xml file against an external DTD. The below
code allows me to read the xml file and gather specific elements of
interest.

If the xml looked like this, How would i validate it ?
<?xml version='1.0' encoding='utf-8' standalone='yes'?>
<simpsons type='bank' platform='TV' app-version='1.0.0'>
    <header>
        <id>845314490</id>
        <title>IN_SF_EN_MA_G2_CA_2009_00</title>
    </header>
    <font-table>
        <font-entry number='1'>
            <charset>ansi</charset>
            <name>Arial</name>
            <pitch>default</pitch>
        </font-entry>
        <font-entry number='2'>
            <charset>ansi</charset>
            <name>Times New Roman</name>
            <pitch>variable</pitch>
            <family>roman</family>
        </font-entry>
    </font-table>
    ....
</simpsons>

Thanks.

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;

import org.xml.sax.helpers.DefaultHandler;

public class ParseXml extends DefaultHandler{

    private SAXParserFactory spf;
    private Examview tempExamviewObj; //to maintain context

    private List myExamviewArrayList;

    private String tempVal;
    private String filename;

    public ParseXml(){
        this.myExamviewArrayList = new ArrayList();
    }
    public Iterator getExamviewIterator(){
         return myExamviewArrayList.iterator();
    }
    public void parse(String filename) {
        this.filename = filename;
        parseDocument(filename);
    }
    private void parseDocument(String filename) {

        //get a factory
        this.spf = SAXParserFactory.newInstance();
        try {

            //get a new instance of parser
            SAXParser sp = this.spf.newSAXParser();

            //parse the file and also register this class for call backs
            sp.parse(filename, this);

        }catch(SAXException se) {
            se.printStackTrace();
        }catch(ParserConfigurationException pce) {
            pce.printStackTrace();
        }catch (IOException ie) {
            ie.printStackTrace();
        }
    }

    //Event Handlers
    public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
        //reset
        tempVal = "";
        if(qName.equalsIgnoreCase("examview")) {
            //create a new instance of Examview
            tempExamviewObj = new Examview();
            tempExamviewObj.setPlatform(attributes.getValue("platform"));
            tempExamviewObj.setAppVersion(attributes.getValue("app-version"));
        }
    }

    public void characters(char[] ch, int start, int length) throws
SAXException {
        tempVal = new String(ch,start,length);
    }

    public void endElement(String uri, String localName, String qName)
throws SAXException {

        if(qName.equalsIgnoreCase("Examview")) {
            tempExamviewObj.setFileName(this.filename);

            //add it to the list
            myExamviewArrayList.add(tempExamviewObj);

        }else if (qName.equalsIgnoreCase("id")) {
            tempExamviewObj.setId(tempVal);
        }else if (qName.equalsIgnoreCase("title")) {
            tempExamviewObj.setTitle(tempVal);
        }else if (qName.equalsIgnoreCase("topic")) {
            //System.out.println("Topic:" + tempVal.trim());
            tempExamviewObj.addTopic(tempVal);
        }else if (qName.equalsIgnoreCase("question")) {
            tempExamviewObj.updateQuestionCount();
        }

    }
}