title: pass variable in xml and read out
body: <pre><code>double summe = 11.11;
  String XML = "&lt;?xml version=\"1.0\" encoding=\"UTF-8\"?&gt;\n" +
               "  &lt;amount&gt; summe &lt;/amount&gt;\ "
               "  &lt;currency_code&gt;EUR&lt;/currency_code&gt;"
  </code></pre>
  
  <p>I want to overwrite the value sum in the xml.</p>