org.w3c.xml 中 getChildNodes()方法需要注意

To   get   the   element's   children   (which   may   be   subelements,   text,   

comments,   or   other   nodes),   use   the   getChildNodes   method.   That   

method   returns   a   collection   of   type   NodeList.   That   type   was   

invented   before   the   standard   Java   collections,   and   it   has   a   

different   access   protocol.   The   item   method   gets   the   item   with   a  

 given   index,   and   the   getLength   method   gives   the   total   count   of  

 the   items.   Therefore,   you   can   enumerate   all   children   like   this:  
   
  NodeList   children   =   root.getChildNodes();  
  for   (int   i   =   0;   i   <   children.getLength();   i++)  
  {  
        Node   child   =   children.item(i);  
        .   .   .  
  }  
   
  You   have   to   be   careful   when   analyzing   the   children.   Suppose   

for   example   that   you   are   processing   the   document  
   
  <font>  
        <name>Helvetica</name>  
        <size>36</size>  
  </font>  
   
  You   would   expect   the   font   element   to   have   two   children,   but   

the   parser   reports   five:  
  The   whitespace   between   <font>   and   <name>  
  The   name   element    
  The   whitespace   between   </name>   and   <size>    
   
  The   size   element    
   
  The   whitespace   between   </size>   and   </font>    
  If   you   only   expect   subelements,   then   you   can   ignore   the   

whitespace:  
   
  for   (int   i   =   0;   i   <   children.getLength();   i++)  
  {  
        Node   child   =   children.item(i);  
        if   (child   instanceof   Element)  
        {  
              Element   childElement   =   (Element)child;  
              .   .   .  
        }  
  }