It's not something that users won't figure out eventually, but it would be 
helpful if the Javadoc for XMLSerializer(java.io.Writer writer, OutputFormat 
format) were amended to read:

Constructs a new serializer that writes to the specified writer using the 
specified output format. If format is null, will use a default output format.

WARNING: FileWriter seems convenient, but it probably *won't* reliably do what 
you think it will for this purpose and will likely fail when you least expect 
it. Use an OutputStreamWriter explicitly specifying UTF-8 as a Charset 
instead. 

Example:

// No, no, a billion times NO! --> FileWriter writer = new FileWriter(file);
FileOutputStream outputStream = new FileOutputStream(file);
Charset utf8 = Charset.forName("UTF-8");
OutputStreamWriter writer = new OutputStreamWriter(outputStream, utf8);
XMLSerializer serializer = new XMLSerializer(writer, formatter);