XML set Node Value help needed

Hello,

I have a XML file NAME.XML, I can read the XML and get the node names. The only thing is that I can't (or don't know how) to set new value to empty node. Here is the XML example:

<city>
<person>
<name /> // here must be set the new value.
<age>25<age/>
</person>
</city>

The name is a simple string like String name = "Sponger Bob";
Any help please?
Thanks in advance.