class MultilineMessageHelper {

    private static final int DEFAULT_MAX_SIZE = 65;
    private static final char BOX_CHAR = '*';

    private static final Pattern S_FILTER = Pattern.compile("\\s+");

    public static String separatorLine() {<FILL_FUNCTION_BODY>}

    public static List<String> format(String... lines) {
        int size = DEFAULT_MAX_SIZE;
        int remainder = size - 4; // 4 chars = 2 box_char + 2 spaces
        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) {
                if (sb.length() >= remainder - word.length() - (sb.length() > 0 ? 1 : 0)) {
                    repeat(sb, ' ', remainder - sb.length());
                    result.add(BOX_CHAR + " " + sb + " " + BOX_CHAR);
                    sb.setLength(0);
                }
                if (sb.length() > 0) {
                    sb.append(' ');
                }
                sb.append(word);
            }

            while (sb.length() < remainder) {
                sb.append(' ');
            }
            result.add(BOX_CHAR + " " + sb + " " + BOX_CHAR);
        }
        // last line
        sb.setLength(0);
        repeat(sb, BOX_CHAR, size);
        result.add(sb.toString());
        return result;
    }

    private static void repeat(StringBuilder sb, char c, int nb) {
        for (int i = 0; i < nb; i++) {
            sb.append(c);
        }
    }
}

        StringBuilder sb = new StringBuilder(DEFAULT_MAX_SIZE);
        repeat(sb, '*', DEFAULT_MAX_SIZE);
        return sb.toString();
    
<no_super_class>