List<String> result = new ArrayList<>();
        StringBuilder sb = new StringBuilder(size);
        // first line
        sb.setLength(0);
        repeat(sb, BOX_CHAR, size);
        result.add(sb.toString());
        // lines
        for (String line : lines) {
            sb.setLength(0);
            String[] words = S_FILTER.split(line);
            for (String word : words) {