Calculate date

[Pramod P Deore]

I want to print a date of one year later. I tried to write the program but it will not print day properly(it calculate year and month correctly).

import java.util.*;
class DateTest
{
	public static void main(String[] args)
	{		
		Date today =new Date();
		int year = today.getYear();
		int month = today.getMonth();
		int day = today.getDay();
		Date nextDate = new Date(year+1,month,day);
		System.out.println (nextDate);
		System.out.println (today);
		System.out.println (today.after(nextDate));
	} 
}

but nextDate is not giving me the exam date of nect year . out put is

Sat Apr 30 00:00:00 IST 2011
Sun May 23 12:01:38 IST 2010
false

Here year is correct i.e 2011 but month and date is not what I want.(I want month as May and date as 23)

Thanks in advance

[Pramod P Deore]

When I calculate nextDate as

  Date nextDate = new Date(year+1,month+1,day-8);  

then it prints correct date after one year as

 Mon May 23 00:00:00 IST 2011
Sun May 23 12:07:13 IST 2010
false
   

But why is it so? Is this right? or there is another option to calculate date of next year?

[Mike Simmons]

You need to read the Date API. In particular, pay attention where they use the term "deprecated". On just about every method you use here. Read what they say about what you should do instead.

[Pramod P Deore]

I didn't get how to find it using GregorianCalendar. Anybody knows?

[Rob Spoor]

You already have a class that can do what you want. You want to add one year to the calendar object. Are you sure you can't find a method to do that?

[Mike Simmons]

Rob Prime wrote:You already have a class that can do what you want. You want to add one year to the calendar object. Are you sure you can't find a method to do that?

Um, in the code shown so far, he doesn't have a calendar; he has a Date. There are methods in Date that could conceivably be used here, but the API says they're deprecated, and we should use methods in Calendar or GregorianCalendar instead. So that's why he's looking into new classes like GregorianCalendar.

Pramod, can you show what you've tried with GregorianCalendar, or tell us what part of the API is confusing? Sadly, I know many parts of Java's date.time.calendar stuff can be confusing - we just need to focus on the particular part or parts you're having trouble with.

Googling things like "java GregorianCalendar examples" can also be helpful here.

Also I suggest paying careful attention to the difference between getDay() or get(Calendar.DAY) with getDate() or get(Calendar.DATE). I think this is actually the biggest problem with your original code.

[Rob Spoor]

Mike Simmons wrote:

Rob Prime wrote:You already have a class that can do what you want. You want to add one year to the calendar object. Are you sure you can't find a method to do that?

Um, in the code shown so far, he doesn't have a calendar; he has a Date. There are methods in Date that could conceivably be used here, but the API says they're deprecated, and we should use methods in Calendar or GregorianCalendar instead. So that's why he's looking into new classes like GregorianCalendar.

I know, he found that one:

Pramod P Deore wrote:I didn't get how to find it using GregorianCalendar. Anybody knows?

That was the class I was talking about.

[Mike Simmons]

Hmm, OK. The "already" sounded to me like a reference to the earlier class found. As opposed to the one he just found.

[Pramod P Deore]

Hi, Rob and Mike Thanks for reply, I think now I got it. I had used now get(int ), roll(int,int) and compareTo method as follows

import java.util.*;
class DateTest
{
	public static void main(String[] args)
	{		
		GregorianCalendar today = new GregorianCalendar();
		
		System.out.println (today);

		//get current yea,month,day value
		int year = today.get(1);
		int month = today.get(2);
		int day = today.get(5);

		System.out.println (year);
		System.out.println (month);
		System.out.println (day);

		//increment current year by one	
		GregorianCalendar today1 = new GregorianCalendar();	
		today1.roll(1,1);
		int year1 = today1.get(1);
		int month1 = today1.get(2);
		int day1 = today1.get(5);
	
		System.out.println ("##############"+year1);
		System.out.println ("##############"+month1);
		System.out.println ("##############"+day1);

		
		int diff = today1.compareTo(today);
		System.out.println ("@@@@@@@"+diff);
		
		
	} 
}

Once again Thanks

[Rob Spoor]

Don't use 1, 2 and 5. For anyone reading your code, including yourself in a few weeks / months, they mean nothing. Use the constant names:

int year = today.get(Calendar.YEAR); // not 1
int month = today.get(Calendar.MONTH); // not 2
int day = today.get(Calendar.DAY_OF_MONTH); // not 5
...  
today1.roll(Calendar.YEAR, 1); // not 1

Like I said, 1, 2 and 5 mean nothing to me. Calendar.YEAR, Calendar.MONTH and Calendar.DAY_OF_MONTH make it clear what you're trying to do.

[Pramod P Deore]

Thanks Rob, for correcting me.

[Rob Spoor]

You're welcome.