<string name="date_time_format">dd MMMM yyyy, hh.mm a</string>
<string name="date_time_format">dd.MM.yyyy, HH:mm</string>

SimpleDateFormat fmtOut = new SimpleDateFormat(context.getString(R.string.date_time_format), Locale.getDefault());

<string name="date_time_string">%s</string>
<string name="date_time_string">%s Uhr</string>

return String.format(context.getString(R.string.date_time_string), fmtOut.format(date));

java.sql.Date date1 = new java.sql.Date((new Date()).getTime());

        SimpleDateFormat formatNowDay = new SimpleDateFormat("dd");
        SimpleDateFormat formatNowYear = new SimpleDateFormat("yyyy");
        SimpleDateFormat sdf12 = new SimpleDateFormat("hh:mm aa");
        SimpleDateFormat sdf24 = new SimpleDateFormat("HH:mm");
        SimpleDateFormat germanSdf = new SimpleDateFormat("dd.MM.yyyy");

        String currentDay = formatNowDay.format(date1);
        String currentYear = formatNowYear.format(date1);
        String time12 = sdf12.format(date1);
        String time24 = sdf24.format(date1);

        String germanTime = germanSdf.format(date1);

        Calendar mCalendar = Calendar.getInstance();
        String currentMonth = mCalendar.getDisplayName(Calendar.MONTH, Calendar.LONG, Locale.getDefault());

        String engTime = currentDay+" "+currentMonth+" "+currentYear+", "+time12;
        String germanFormat = germanTime+", "+time24+" Uhr";

DateFormat df = DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, Locale.ENGLISH);

// get device's locale
Locale locale = Locale.getDefault();

String pattern = "";
// check language
if ("en".equals(locale.getLanguage())) {
    // english
    pattern = "dd MMMM yyyy, h.mm a";
} else if ("de".equals(locale.getLanguage())) {
    // german
    pattern = "dd.MM.yyyy, HH:mm 'Uhr'";
} else {
    pattern = // use some default pattern for other languages?
}

SimpleDateFormat sdf = new SimpleDateFormat(pattern, locale);
String formattedDate = sdf.format(new Date());

// change AM/PM to am/pm (only for English)
if ("en".equals(locale.getLanguage())) {
    formattedDate  = formattedDate.toLowerCase();
}

Locale locale = Locale.getDefault();
FormatStyle style = FormatStyle.MEDIUM;
String pattern = DateTimeFormatterBuilder.getLocalizedDateTimePattern(style, style, IsoChronology.INSTANCE, locale);
DateTimeFormatter fmt = DateTimeFormatter.ofPattern(pattern, locale);

// get device's locale
Locale locale = Locale.getDefault();

String pattern = "";
// check language
if ("en".equals(locale.getLanguage())) {
    // english
    pattern = "dd MMMM yyyy, h.mm a";
} else if ("de".equals(locale.getLanguage())) {
    // german
    pattern = "dd.MM.yyyy, HH:mm 'Uhr'";
} else {
    pattern = ""; // use some default pattern?
}

DateTimeFormatter fmt = DateTimeFormatter.ofPattern(pattern, locale);

String formattedDate = LocalDateTime.now().format(fmt);

// map of formatters
Map<String, DateTimeFormatter> formatterMap = new HashMap<>();

// English formatter
Map<Long, String> customAmPmSymbols = new HashMap<>();
customAmPmSymbols.put(0L, "am");
customAmPmSymbols.put(1L, "pm");
DateTimeFormatter f = new DateTimeFormatterBuilder()
    // date/time
    .appendPattern("dd MMMM yyyy, h.mm ")
    // custom AM/PM symbols (lowercase)
    .appendText(ChronoField.AMPM_OF_DAY, customAmPmSymbols)
    // create formatter
    .toFormatter(Locale.ENGLISH);
// add to map
formatterMap.put("en", f);

// German formatter
formatterMap.put("de", DateTimeFormatter.ofPattern("dd.MM.yyyy, HH:mm 'Uhr'", Locale.GERMAN));

// get device's locale
Locale locale = Locale.getDefault();

DateTimeFormatter fmt = formatterMap.get(locale.getLanguage());

if (fmt != null) {
    String formattedDate = LocalDateTime.now().format(fmt);
}