my code to insert new cred-pair at desried machine level.
Document insertNewNode(String loginId,String pass,String machine_name)
{
List<?> list1 = document.selectNodes("//machine/@name" );
Iterator<?> itr=list1.iterator();
while(itr.hasNext()){
Attribute attribute=(Attribute)itr.next();
if( attribute.getValue().equals(machine_name))
{
List<?> list1 = document.selectNodes("//machine" );
...