public static void appendQuotedChar(Appendable sb, int c) {
        int q = 0;
        if (c == '\b')
            q = 'b';
        else if (c == '\n')
            q = 'n';
        else if (c == '\r')
            q = 'r';
        else if (c == '\t')
            q = 't';
        else if (c == '\"' || c == '\\')
            q = c;
        if (q != 0) {
            append(sb, '\\');
            append(sb, (char) q);
        } else if (c >= 127 || c < 20) {
            append(sb, '\\');
            append(sb, 'u');
            Util.hex(sb, c, 4);
        } else
            append(sb, (char) c);
    }