[java] How to convert an Instant to a date format?

I can convert a java.util.Date to a java.time.Instant (Java 8 and later) this way:

Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR_OF_DAY, 8);
cal.set(Calendar.MINUTE, 30);
Date startTime = cal.getTime();
Instant i = startTime.toInstant();

Can anybody let me know about the convert that instant to date with a specific date & time format? i.e 2015-06-02 8:30:00

I have gone through api but could not find a satisfactory answer.

Instant i = Instant.ofEpochSecond(cal.getTime);

Read more here and here

An Instant is what it says: a specific instant in time - it does not have the notion of date and time (the time in New York and Tokyo is not the same at a given instant).

To print it as a date/time, you first need to decide which timezone to use. For example:

System.out.println(LocalDateTime.ofInstant(i, ZoneOffset.UTC));

This will print the date/time in iso format: 2015-06-02T10:15:02.325

If you want a different format you can use a formatter:

LocalDateTime datetime = LocalDateTime.ofInstant(i, ZoneOffset.UTC);
String formatted = DateTimeFormatter.ofPattern("yyyy-MM-dd hh:mm:ss").format(datetime);
System.out.println(formatted);

If you want to convert an Instant to a Date:

Date myDate = Date.from(instant);

And then you can use SimpleDateFormat for the formatting part of your question:

SimpleDateFormat formatter = new SimpleDateFormat("dd MM yyyy HH:mm:ss");
String formattedDate = formatter.format(myDate);

try Parsing and Formatting

Take an example Parsing

String input = ...;
try {
    DateTimeFormatter formatter =
                      DateTimeFormatter.ofPattern("MMM d yyyy");
    LocalDate date = LocalDate.parse(input, formatter);
    System.out.printf("%s%n", date);
}
catch (DateTimeParseException exc) {
    System.out.printf("%s is not parsable!%n", input);
    throw exc;      // Rethrow the exception.
}

Formatting

ZoneId leavingZone = ...;
ZonedDateTime departure = ...;

try {
    DateTimeFormatter format = DateTimeFormatter.ofPattern("MMM d yyyy  hh:mm a");
    String out = departure.format(format);
    System.out.printf("LEAVING:  %s (%s)%n", out, leavingZone);
}
catch (DateTimeException exc) {
    System.out.printf("%s can't be formatted!%n", departure);
    throw exc;
}

The output for this example, which prints both the arrival and departure time, is as follows:

LEAVING:  Jul 20 2013  07:30 PM (America/Los_Angeles)
ARRIVING: Jul 21 2013  10:20 PM (Asia/Tokyo)

For more details check this page- https://docs.oracle.com/javase/tutorial/datetime/iso/format.html