added new API to the Reporter class. One of the new methods added to the interface was not declared with a default implementation. Although not strictly required in normal usage with javadoc, it is the prevailing convention to provide some sort of default implementation.
The method in question is
void print(Diagnostic.Kind kind, FileObject file, int start, int pos, int end, String message);
There is no reasonable default behavior other than to throw UnsupportedOperationException.