java.util.Date format SSSSSS: if not microseconds what are the last 3 digits?

Question

Just tested this code on both my Windows (8) workstation and an AIX:

    public static void main(String[] args) {
        System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSSSS").format(new Date()));
        System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSSSS").format(new Date()));
    }

and got something similar to this as a result:

2013-10-07 12:53:26.000905
2013-10-07 12:53:26.000906

Can someone please explain me what are the last digits, if not microseconds?

Note: I interact with a DB2 database in which chronological data is stored using timed columns as TIMESTAMP with 6 digits AFTER the seconds i.e. microseconds (IMO). But all those "timestamps" are created by requesting the following query:

SELECT current timestamp as currenttimestamp FROM Table ( values (1)) temp

I wonder if, given the above results, I couldn't just use in my code new Date() instead of selecting the current timestamp from the database.

Thanks.

PS: I searched but found no relevant (answered) questions, like: Current time in microseconds in java or Get time with hour, minute, second, millisecond, microsecond

Answer 1

From the documentation of SimpleDateFormat:

Letter     Date or Time Component     Presentation     Examples  
S          Millisecond                Number           978 

So it is milliseconds, or 1/1000th of a second. You just format it with on 6 digits, so you add 3 extra leading zeroes...

You can check it this way:

    Date d =new Date();
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.S").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SS").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSS").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSSS").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSSSS").format(d));

Output:

2013-10-07 12:13:27.132
2013-10-07 12:13:27.132
2013-10-07 12:13:27.132
2013-10-07 12:13:27.0132
2013-10-07 12:13:27.00132
2013-10-07 12:13:27.000132

(Ideone fiddle)