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);