sqlite convert timestamp to date

how to convert timestamp value 444663422.631236 to date. I tried these ways but does not worked.

public class Teste {
public static void main(String[] args) throws ParseException {
    String l = "480364794";
    String d = "479617200";

    print(convertEpoc("444663422"));

    print(convert("480364794", "dd/MM/yyyy HH:mm:ss"));
    print(convert("479617200", "dd/MM/yyyy HH:mm:ss"));

}

private static String convertEpoc(String d) {
    long epoch = Long.parseLong(d);
    Instant instant = Instant.ofEpochMilli(epoch * 1000);
    ZonedDateTime.ofInstant(instant, ZoneOffset.UTC);
    return instant.toString();
}

public static String convert(String epochSec, String dateFormatStr) {
    Date date = new Date(Long.parseLong(epochSec) * 1000);
    SimpleDateFormat format = new SimpleDateFormat(dateFormatStr,
            Locale.getDefault());
    return format.format(date);
}

public static void print(String s) {
    System.out.println(s);
}}

what am i doing wrong?