Format

    public static void main(String... strings) {
        // Old
        final String old1 = DateFormat.format_yyyyMMdd(new Date());
        final String old2 = DateFormat.format_yyyy_MM_dd(new Date());
        // New
        final String new1 = format(LocalDate.now(), YYMMDD_PATTERN);
        final String new2 = format(LocalDate.now(), YY_MM_DD_PATTERN);
        System.out.println(Objects.equals(old1, new1));
        System.out.println(Objects.equals(old2, new2));

        long currentMs = System.currentTimeMillis();
        DateFormat.format(currentMs);

    }

    /**************
     * OLD SOURCE CLONE
     **************
     */
     public static final int JavaDate_StartYear = 1900;
    private static final String Zero = "0";
    private static String format2DNumber(int n) {
        return n > 9 ? String.valueOf(n) : (Zero + n);
    }
    public static String format_yyyyMMdd(Date d) {
        if (d == null) {
            return null;
        }
        StringBuilder buidler = new StringBuilder()
                .append(d.getYear() + JavaDate_StartYear)
                .append(format2DNumber(d.getMonth() + 1))
                .append(format2DNumber(d.getDate()));
//                .append( getMillisecond( d ) );
        return buidler.toString();
    }

    public static String format_yyyy_MM_dd(Date d) {
        if (d == null) {
            return null;
        }
        StringBuilder buidler = new StringBuilder()
                .append(d.getYear() + JavaDate_StartYear)
                .append("_")
                .append(format2DNumber(d.getMonth() + 1))
                .append("_")
                .append(format2DNumber(d.getDate()));
//                .append( getMillisecond( d ) );
        return buidler.toString();
    }
    // End
    /**************
     * NEW SOURCE CLONE
     **************
     */
    private static final DateTimeFormatter YYMMDD_PATTERN = DateTimeFormatter.ofPattern("yyyyMMdd");
    private static final DateTimeFormatter YY_MM_DD_PATTERN = DateTimeFormatter.ofPattern("yyyy_MM_dd");

    public static final String format(TemporalAccessor temporal, DateTimeFormatter formatter) {
        return formatter.format(temporal);
    }
    // End