java - Android SimpleDateFormat, how to use it?

Question

I am trying to use the Android SimpleDateFormat like this:

String _Date = "2010-09-29 08:45:22"
SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");

try {
    Date date = fmt.parse(_Date);
    return fmt.format(date);
}
catch(ParseException pe) {
    return "Date";    
}

The result is good and I have: 2010-09-29

But if I change the SimpleDateFormat to

SimpleDateFormat("dd-MM-yyyy");

the problem is that I will got 03-03-0035 !!!!

Why and how to get the format like dd-MM-yyyy?

Answer 1

I assume you would like to reverse the date format?

SimpleDateFormat can be used for parsing and formatting. You just need two formats, one that parses the string and the other that returns the desired print out:

SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
Date date = fmt.parse(dateString);

SimpleDateFormat fmtOut = new SimpleDateFormat("dd-MM-yyyy");
return fmtOut.format(date);

Since Java 8:

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("yyyy-MM-dd").withZone(ZoneOffset.UTC);
TemporalAccessor date = fmt.parse(dateString);
Instant time = Instant.from(date);

DateTimeFormatter fmtOut = DateTimeFormatter.ofPattern("dd-MM-yyyy").withZone(ZoneOffset.UTC);
return fmtOut.format(time);