Application to Detect Non-UTF-8 Characters in XML

I just need a simple application with a very basic UI that takes as input a selected XML document (may be a large XML document over 200mb) and detects elements that contain non-UTF characters.? The application should display any non-UTF characters that are in the data.? A simple AWT interface would be satisfactory, allowing users to browse for the input XML file.? Please keep in mind XML documents may be very large.? The purpose of the application is to detect those characters that would cause the SAX parser to throw exceptions such as: Invalid byte 2 of 2-byte UTF-8 sequence Invalid byte 2 of 4-byte UTF-8 sequence