@Override
synchronized public RDFErrorHandler setErrorHandler(RDFErrorHandler errHandler) {
// null means no user defined error handler.
// We implement this using defaultErrorHandler,
// but hide this fact from the user.
RDFErrorHandler rslt = errorHandler;
if (rslt == defaultErrorHandler) rslt = null;
errorHandler = errHandler == null ? defaultErrorHandler : errHandler;
return rslt;
}