帮我看看SAX解析XML的两个函数是怎么调用的？

该程序是如何调用characters1(char ch[], int start, int length)和startElement(String uri,String localName,String qName,Attributes attrs)？
不像是继承过来的方法？


Java code:

package SAX;

import org.xml.sax.*;
import org.xml.sax.helpers.*;
import javax.xml.parsers.*;

public class MyXMLReader extends DefaultHandler {

java.util.Stack tags = new java.util.Stack();
public MyXMLReader() {
super();
}

public static void main(String args[]) {
long lasting = System.currentTimeMillis();
try {
SAXParserFactory sf = SAXParserFactory.newInstance();
SAXParser sp = sf.newSAXParser();
MyXMLReader reader = new MyXMLReader();
sp.parse(new InputSource("data_10k.xml"), reader);
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("运行时间：" + (System.currentTimeMillis() - lasting) + " 毫秒");
}

public void characters1(char ch[], int start, int length) throws SAXException {
System.out.println("characters()");
String tag = (String) tags.peek();
if (tag.equals("NO")) {
System.out.print("车牌号码：" + new String(ch, start, length));
}
if (tag.equals("ADDR")) {
System.out.println(" 地址:" + new String(ch, start, length));
}
}

public void startElement(String uri,String localName,String qName,Attribut