When I run the follow codes, the result is '28'
Date date = new Date(2000,2, 1);
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.MONTH, -1);
int value = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
System.out.println(value);
But, I change "Date date = new Date(2000,2, 1);" to "Date date = new Date(2004,2, 1);" , The value is '29'
Thanks your help!
Best Regards
Xue
Sorry! I forgot the follow code:
cal.add(Calendar.YEAR, -1900);
the follow codes is right:
Date date = new Date(2000,2, 1);
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.MONTH, -1);
cal.add(Calendar.YEAR, -1900);
int value = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
System.out.println(value);
Thanks a lots!
I am not good at the class Date and Calender.
the follow codes is ok!
After creating "Date date = new Date(2000,2, 1);", the year must do "cal.add(Calendar.YEAR, -1900);", and the month must do "cal.add(Calendar.MONTH, -1);".
Now, the problem is solved.
Date date = new Date(2000,2, 1);
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.MONTH, -1);
cal.add(Calendar.YEAR, -1900);
intmonth_day_score = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
> Now, the problem is solved.
I'm curious. What was the original problem exactly? Your code sets the calendar time to 1 March 3900: why? Then it subtracts 1900 the hard way, when it should have been subtracted in the Date constructor. Then it calculates the number of days in January 2000. Which was 29.
If that's not what you were trying to do, you've still got a problem.
>Right. I still don't know what this Date in the year 3900 was for.
It shuold be 28.
I post the integrated codes:
/**
* Get the day numbers of the <code>month</code> in the <code>year</code>
* Example, If you want to know the day number of Feb,2000,
* the month is 2 and year is 2000.
* @param year The year that you need.
* @param month The month that you need.
* @return The number of the <code>month</code> in the <code>year</code>
*
*/
public int getDays(String year,String month){
int y=Integer.parseInt(year);
int m=Integer.parseInt(month);
Date date = new Date(y,m, 1);
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.MONTH, -1);
cal.add(Calendar.YEAR, -1900);
intmonth_day_score = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
return month_day_score;
}
So you still have a bug because the year argument to Date(int year, int month, int day) is years since 1900, not years since 0CE or 0AD or whatever you want to call it. This is your real problem. Once you've fixed this you can forget about subtracting 1900 from the date and you'll probably then end up in the right year and get the result you're expecting.
Your Javadoc says that you just pass in the year that you need, and you are parsing this as an integer and then passing the result as the first parameter to the constructor for Date. You should be subtracting 1900 from the year value at this point according to the Javadoc for java.util.Date. And therefore you don't need to subtract 1900 later on.