First of all, note that what you posted is not valid XML - it does not have one single root element. I hope that's not actually what Google Health uses.
Both the DOM and SAX APIs can read from an InputStream (which is easily constructed from a String). Check the java.xml.parsers.DocumentBuilder and SAXParser javadocs for the relevant methods. Basic examples of how to use both can be found here, particularly e510 and e517.