add 10 days to currentDate in java.util.Date or cast to Calendar?

[nimo frey]

I know, I can add or substract days, years,.. from an actual Calenar-Instance.

But how can I do it with the java.util.Date?

For example

Date myDate = new Date();
myDate.setMonth(a.getMonth()+1);

But setMonth is depraceted, so I should use Calendar.

But how can I convert /cast a Calendar-Instance to a Date-Instance, when I need the Date?

Or should I better cast a Date-Instance to Calendar-Instance, how?

[Jesper de Jong]

You cannot cast a Date to a Calendar, or a Calendar to a Date, because those two classes are not related in the class hierarchy. Trying to cast one into the other will lead to a ClassCastException.

Class Calendar contains setTime() and getTime() methods to set the Calendar to the date and time of a Date object, or to get a Date object that represents the date and time that a Calendar is set to. Lookup those methods in the API documentation of class Calendar.

Date date = ...; // wherever you get this from

Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.DATE, 10); // add 10 days

date = cal.getTime();

[nimo frey]

hello,

thanks! yes that works!

Do you know, how I convert this Date to a Timestamp.

For example, I want to compare Date and Timestamp and have to convert Date into a Timestamp-Instance.

I have this date:

Tue Jan 14 00:00:00 GMT 2009

and this Timestamp:

1990-01-09 00:00:00.000000

how can I convert my date into a Timestamp-Instance

[Tom Johnson]

I think SimpleDateFormatter should have something along the lines of what you want

[nimo frey]

Look at this, I have Date-Instance and set the Time of my Calender-Instance via

	     Calendar cal= Calendar.getInstance();
	     cal.setTime(myDateInstance);

But there are difference between the year, month,.... Only the getTime are equals:

15:10:56,600 INFO  [log] DATE-INSTANCE
15:10:56,600 INFO  [log] YEAR: 109
15:10:56,600 INFO  [log] MONTH: 1
15:10:56,600 INFO  [log] DAY: 20
15:10:56,600 INFO  [log] MINUTE: 0
15:10:56,600 INFO  [log] HOUR: 0
15:10:56,600 INFO  [log] SECOND: 0
15:10:56,600 INFO  [log] string 20 Feb 2009 00:00:00 GMT

15:10:56,600 INFO  [log] CALENDAR-INSTANCE
15:10:56,600 INFO  [log] YEAR: 1
15:10:56,600 INFO  [log] MONTH: 2
15:10:56,600 INFO  [log] DAY_OF_MONTH: 5
15:10:56,600 INFO  [log] cal.getTime Fri Feb 20 00:00:00 GMT 2009

What is my fault?

[Tom Johnson]

How is myDateInstance declared & initialised?

[nimo frey]

The Value of myDateInstance which is a Instance of Date-Object is set to that date:

20 Feb 2009 00:00:00 GMT

The Calendar-Instance returns exactly that date when using cal.getTime.
But when using cal.MONTH, then it returns a false month.

[Tom Johnson]

Why dont you just post whole code so we can see what you are doing?

[nimo frey]

I do not know why there is a difference between the Year, Month,.. of Date-Instance and Calendar-Instance. However the getTime returns an equal date.

Well, the problem to get a Timestamp-String is solved via SimpleDateFormat.

thanks.

[Rob Spoor]

1) You seem to be printing the contents of the constants, not the fields of the calendar represented by those fields. You should use calendar.get(Calendar.MONTH), not just Calendar.MONTH

2) Months in Date and Calendar are 0-based. 1 does not mean January but February. To make it easier, compare to the constants like Calendar.FEBRUARY instead of comparing to the literal 1

3) Years in Date should have 1900 added. 109 actually means 1900 + 109, being 2009

[nimo frey]

okay,

so I should use this:

Calendar cal= Calendar.getInstance();

cal.set(Calendar.DATE, Calendar.DATE+10);

instead of this?:

Calendar cal= Calendar.getInstance();
cal.add(Calendar.DATE, 10);

I found out that the second approach works for years, months and minutes, but not for 'seconds':

Calendar cal= Calendar.getInstance();
// this does work, increment 10 days
cal.add(Calendar.DATE, 10);
// this does NOT work, as no increment of 10 seconds
cal.add(Calendar.SECOND, 10);

[nimo frey]

I cannot manipulate the seconds.

I can manipulate Month, Year, Minute, Day but not SECOND.

Why is that so?

[Tom Johnson]

nimo frey wrote:I cannot manipulate the seconds.

I can manipulate Month, Year, Minute, Day but not SECOND.

Why is that so?

You can manipulate the second:

final Calendar cal = Calendar.getInstance();
System.out.println(cal.getTime());
cal.set(Calendar.SECOND, cal.get(Calendar.SECOND) + 12);
System.out.println(cal.getTime());

Output for me was
Fri Jan 30 16:32:10 GMT 2009
Fri Jan 30 16:32:22 GMT 2009

Note that 12 was added to the seconds value

[Rob Spoor]

nimo frey wrote:okay,

so I should use this:

Calendar cal= Calendar.getInstance();

cal.set(Calendar.DATE, Calendar.DATE+10);

instead of this?:

Calendar cal= Calendar.getInstance();
cal.add(Calendar.DATE, 10);

If possible, add still has preferecen if you want to add days etc.