for (File file : getGrammarFiles()) {
            commandLine.add(file.getAbsolutePath());
        }

        return commandLine;
    }

    public Set<File> getInputDirectories() {
        return inputDirectories;
    }

        /**
         * process used for antlr3/4
         */
        public AntlrResult doProcess(AntlrSpec spec) throws ClassNotFoundException {
            int numErrors = 0;
            if (spec.getInputDirectories().size() == 0) {
                // we have not root source folder information for the grammar files,
                // so we don't force relativeOutput as we can't calculate it.