private boolean isForbidden(final char c) {
        // surrogates, U+FFFE and U+FFFF are forbidden in XML.
        return c == '\ufffe' || c == '\uffff';
    }
Determines if the supplied characters is forbidden in XML, even as a character reference.

@param c The char to test.
@return True if the char is forbidden.
stroom-legacy/stroom-legacy-model_6_1/src/main/java/stroom/legacy/model_6_1/MyXmlEmitter.java