private static boolean isLegalJavaIdentifier(String name) {
        if (name.isEmpty()) return false;
        if (! Character.isJavaIdentifierStart(name.charAt(0))) return false;

        for (char c : name.substring(1).toCharArray()) {
            if (! Character.isJavaIdentifierPart(c)) return false;
        }
        return true;
    }
Create class name from def name

@param defName the file name without the '.def' suffix
configgen/src/main/java/com/yahoo/config/codegen/ConfiggenUtil.java