setTextContent编辑XML文件内容没变化

Java code:
/**
* 设置指定的元素名和节点索引所对应节点的内容
* @param 元素名
* @param 节点索引
* @param 内容
*/
public void setElementContent(String elementName,int nodeIndex,String newContext){
try{
NodeList nodeList=doc.getElementsByTagName(elementName);
Node node0=nodeList.item(nodeIndex);
node0.setTextContent(newContext);
}catch(DOMException e){
System.out.println(e.toString().replaceAll("\n", ""));
}

public static void setParmeter(String xmlPath,HashMap indexHP, HashMap valueHP){
XmlDocumentManager xml=new XmlDocumentManager(xmlPath);
xml.setElementContent("property", Integer.parseInt(indexHP.get("dialect").toString()), valueHP.get("dialect").toString());
xml.setElementContent("property", Integer.parseInt(indexHP.get("driver").toString()), valueHP.get("driver").toString());
xml.setElementContent("property", Integer.parseInt(indexHP.get("url").toString()), valueHP.get("url").toString());
xml.setElementContent("property", Integer.parseInt(indexHP.get("username").toString()), valueHP.get("username").toString());
xml.setElementContent("property",