package?test_XML;

import?java.io.IOException;

import?javax.xml.parsers.DocumentBuilder;
import?javax.xml.parsers.DocumentBuilderFactory;
import?javax.xml.parsers.ParserConfigurationException;

import?org.w3c.dom.Document;
import?org.w3c.dom.NamedNodeMap;
import?org.w3c.dom.Node;
import?org.w3c.dom.NodeList;
import?org.xml.sax.SAXException;

public?class?DOM_XML_Test?{
	public?static?void?main(String[]?args){
	
		try?{
			DocumentBuilderFactory?dbf?=?DocumentBuilderFactory.newInstance();
	
			DocumentBuilder?db?=dbf.newDocumentBuilder();

				
				Document?document?=?db.parse("book.xml");
				NodeList?bookList?=?document.getElementsByTagName("book");
				System.out.println("咱們書店共有"+bookList.getLength()+"本書");
				for(int?i=0;i<bookList.getLength();i++){
					System.out.println("下面開始遍歷第"+(i+1)+"本書的內(nèi)容");

					Node?book?=?bookList.item(i);

					NamedNodeMap?attributes=book.getAttributes();
					System.out.println("第"+(i+1)+"本書共有"+attributes.getLength()+"個(gè)屬性");
					for(int?j=0;?i<attributes.getLength();j++){
						Node?attr?=?attributes.item(j);
						System.out.print("屬性名"+attr.getNodeName());
						System.out.print("屬性值"+(String)attr.getNodeValue());
					}
				}
				
				}?catch?(SAXException?e)?{
					e.printStackTrace();
				}?catch?(IOException?e)?{
					e.printStackTrace();
				}?catch?(ParserConfigurationException?e)?{
			e.printStackTrace();
		}
	}
}

找半天沒看明白怎么就有空指針異常了呢？