java.util.Date得到毫秒

Question

I have done the following:

String standardRange = "00:01:01";
SimpleDateFormat rangeFormatter = new SimpleDateFormat("hh:mm:ss");
Date range = rangeFormatter.parse(standardRange);

Now:

range.getTime();

.. I get the output of -3539000 and not 61,000

I'm not sure what I'm doing wrong; when debugging, cdate exists, the attribute contains a fraction , which contains the value 61,000, which is what I want.

Answer 1

The reason you're seeing this is that the date you're creating is actually in the past of the date epoch, not 1m1s after it:

String standartRange = "00:01:01";
SimpleDateFormat rangeFormatter = new SimpleDateFormat("hh:mm:ss");
Date range = rangeFormatter.parse(standartRange);

System.out.println(new Date(0L));
System.out.println(new Date(0L).getTime());
System.out.println(range);
System.out.println(range.getTime());

---

and its output;

Thu Jan 01 01:00:00 GMT 1970
0
Thu Jan 01 00:01:01 GMT 1970
-3539000

The epoch date is incorrect here - it should be 00:00:00, but due to a historical bug where BST/GMT changed dates and timezone cant keep track. It seems that Sun/Oracle consider this a historical "inaccuracy".

Check out the bug report - its describes the problem more fully.

From your language (German) this may not be directly due to this BST issue, but its almost certainly related.

Answer 2

Java Date is not designed to calculate the duration of a given time period. The getTime() call returns the numbers of milliseconds since January 1, 1970, 00:00:00 GMT. In your case you are actually ending up with a date that comes before that epoch (thus the negative number). When I run your code I get 21661000. (See the answer from Sean Landsman as I believe he has hit on why you get the negative results...hint: my number is exactly 6 hours off of GMT or 21600000ms)

Joda-Time is a library that is well suited to solving your underlying problem.

PeriodFormatter formatter = new PeriodFormatterBuilder()
         .appendHours()
         .appendSeparator(":")
         .appendMinutes()
         .appendSeparator(":")
         .appendSeconds()
         .toFormatter();
Period period = formatter.parsePeriod("00:01:01");
assert period.toStandardDuration().getMillis() == 61000

Answer 3

To get what you want, you should compare between the time you want and origin of the time. using the below code:

String standardRange = "00:01:01";
SimpleDateFormat rangeFormatter = new SimpleDateFormat("HH:mm:ss");
Date range = rangeFormatter.parse(standardRange);
Date range2 = rangeFormatter.parse("00:00:00");
System.out.println(range.getTime() - range2.getTime());

Answer 4

According to the JavaDoc, getTime() :

Returns the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this Date object.

You want the number of milliseconds in one minute and one second.

(60*minutes+seconds)*1000

It really doesn't need to come from a Date object.

If you need to compute the time in milliseconds for some interval, maybe use the joda time library, or get the day, hour, minute, second and millisecond components out of your date object and compute the value by hand.

Answer 5

Try:

Date range1 = rangeFormatter.parse("00:01:01");
Date range2 = rangeFormatter.parse("00:00:00");
System.out.println(range1.getTime() - range2.getTime());

Answer 6

hh:mm:ss stands for 12-hour time, which always stands for "time point", not "time interval". So surely, time zone will effect the value. However, in GMT +0 the value equals to which represents "time interval".

All you just need is:

rangeFormatter.setTimeZone(TimeZone.getTimeZone("GMT"));

Try it!