title: updating a property of a xml tag
body: <p>Given a xml file as input howto modify a attribute of a tag with a new string value?</p>
  
  <p>Function is </p>
  
  <pre><code>updateXMLAttribute(Document doc , String tag, String attribute, String newValue){
  
  //impl
  </code></pre>
  
  <p>}</p>
  
  <p>How can i do it?</p>