Calendar c = Calendar.getInstance();
c.set(Calendar.MONTH, Calendar.OCTOBER);
c.set(Calendar.DAY_OF_MONTH, 31);
c.set(Calendar.MONTH, c.get(Calendar.MONTH)+1); //Returns Dec 1. Expect Nov 30.
If I have a calendar object and the last day of a month falls on the 31st and the next month has less days than the previous, how can I ensure that by setting the month ahead I will not go beyond the next month?
Use add() instead of set() as the Calendar is "smart" enough to determine the difference of days and such...
public static void main(String[] args) throws Exception {
Calendar c = Calendar.getInstance();
c.set(Calendar.MONTH, Calendar.OCTOBER);
c.set(Calendar.DAY_OF_MONTH, 31);
c.add(Calendar.MONTH, 1);
System.out.println(c.getTime());
}
Output (as of my current run):
Sun Nov 30 09:08:01 EST 2014
According to the Calendar JavaDocs:
Leniency
Calendar has two modes for interpreting the calendar fields, lenient
and non-lenient. When a Calendar is in lenient mode, it accepts a
wider range of calendar field values than it produces. When a Calendar
recomputes calendar field values for return by get(), all of the
calendar fields are normalized. For example, a lenient
GregorianCalendar interprets MONTH == JANUARY, DAY_OF_MONTH == 32 as
February 1.
This means that when you add 1 to the MONTH, the value of DAY_OF_MONTH is still 31. But November doesn't have a 31st day. This means that if the Calendar you are using is lenient, it will interpret MONTH == 11, DAY_OF_MONTH == 31 as December 1.
Related
Hi buddies I'm in a trouble trying to migrate a behavior from calendar to localdate.
payDate.set(Calendar.DAY_OF_MONTH,payDay)
Lets imagine that payDate had the current date, 2020-01-29
for business reasons payDay can had the value of 0, so, when the previous code line is executed with the previous scenario, the result is that payDate update the date to 2019-12-31,
that is to say the the date back to the last day of the past month.
I'm not sure, the technical reason of this, if someone can explain to me this I'll be so thankful, I tried checking the java doc but it was not helpful.
So I need to replicate that behavior with LocalDate java library. From my point of view; the similar of set method from Calendar with the value of DAY_OF_MONTH in LocalDate is:
payDate.withDayOfMonth(payDay)
But when the below scenario is presented and payDay is equal to 0 I get an error:
java.time.DateTimeException: Invalid value for DayOfMonth (valid values 1 - 28/31): 0
Also I had some ideas about how can I get the same result of calendar in localDate when the rule comes on (if payDay is 0, return to the last day of previous month), but are too verbose.
If you know a similar behavior on LocalDate please help me. Thanks.
TL;DR: Use payDate = payDate.plusDays(payDay - payDate.getDayOfMonth());
The behavior of Calendar you're describing is documented in the javadoc:
Leniency
Calendar has two modes for interpreting the calendar fields, lenient and non-lenient. When a Calendar is in lenient mode, it accepts a wider range of calendar field values than it produces. When a Calendar recomputes calendar field values for return by get(), all of the calendar fields are normalized. For example, a lenient GregorianCalendar interprets MONTH == JANUARY, DAY_OF_MONTH == 32 as February 1.
When a Calendar is in non-lenient mode, it throws an exception if there is any inconsistency in its calendar fields. For example, a GregorianCalendar always produces DAY_OF_MONTH values between 1 and the length of the month. A non-lenient GregorianCalendar throws an exception upon calculating its time or calendar field values if any out-of-range field value has been set.
To show the effect of this, try setting the date of a Calendar to January 70, 2020:
Calendar cal = Calendar.getInstance();
cal.clear();
cal.set(2020, Calendar.JANUARY, 70);
System.out.println(new SimpleDateFormat("yyyy-MM-dd").format(cal.getTime()));
Output
2020-03-10
You would get the same result if you did:
cal.set(2020, Calendar.JANUARY, 1);
cal.add(Calendar.DAY_OF_MONTH, 69);
LocalDate is always non-lenient, so you can't set the day-of-month value to a value that is out-of-range. You can however get the same result as what Calendar does, by changing the operation to "add" instead of "set".
So, if you have a particular date, e.g. the 2020-01-29 date mentioned in the question, and you want to "set" the day-of-month value to 70 or 0, with same lenient overflow logic as Calendar has, do this:
LocalDate date = LocalDate.parse("2020-01-29");
date = date.plusDays(70 - date.getDayOfMonth());
System.out.println(date);
LocalDate date = LocalDate.parse("2020-01-29");
date = date.plusDays(0 - date.getDayOfMonth());
System.out.println(date);
Output
2020-03-10
2019-12-31
As you can see, date.plusDays(dayToSet - date.getDayOfMonth()) will give you the desired result.
Here’s how I would go about it:
LocalDate payDate = LocalDate.now(); // or whatever
int payDay = 0;
if (payDay == 0) {
// simulate `GregorianCalendar` behaviour: day 0 is the day before day 1
payDate = payDate.withDayOfMonth(1).minusDays(1);
} else {
payDate = payDate.withDayOfMonth(payDay);
}
System.out.println(payDate);
When I ran the snippet just now, the output was the date you already mentioned:
2019-12-31
If we wanted it shorter, we could use payDate.withDayOfMonth(1).minusDays(1).plusDays(payDay) or the trick from Andreas’ answer, and we would not need the if statement. I would not, though. (1) It’s harder to read. (2) It doesn’t give the validation of payDay that comes for free in the snippet above.
The confusing behaviour of Calendar comes from not range checking the argument to set(). So day 0 of the month is the day before day 1 of the month. Day -1 would be the day before that, and so forth. It’s in this snippet from the documentation (or was supposed to be, at least):
When a Calendar is in lenient mode, it accepts a wider range of
calendar field values than it produces. When a Calendar recomputes
calendar field values for return by get(), all of the calendar
fields are normalized. For example, a lenient GregorianCalendar
interprets MONTH == JANUARY, DAY_OF_MONTH == 32 as February 1.
You may read it with this snippet from the documentation of the setLenient method:
The default is lenient.
Links
Documentation of Calendar
Documentation of Calendar.setLenient()
You're not going to be able to just invoke one method to achieve the same results. If you're sure that setting DAY_OF_MONTH to 0 should cause it to roll back one month (this is the type of thing I'd run past a business analyst or product owner for a sanity check) then you're going to have to do something like this:
int payDay = 0;
LocalDate payDate = LocalDate.of(2020, Month.JANUARY, 29);
if(payDay == 0) {
payDate = payDate.minusMonths(1);
payDay = payDate.lengthOfMonth();
}
payDate = payDate.withDayOfMonth(payDay);
Another approach:
int payDay = 0;
LocalDate payDate = LocalDate.of(2020, Month.JANUARY, 29);
if(payDay == 0) {
payDate = payDate.withDayOfMonth(1).minusDays(1);
} else {
payDate = payDate.withDayOfMonth(payDay);
}
I need to find which nth dayOfWeek a particular day is in the month for a date in Java. For example, today is April 20th, 2016 which is the 3rd Wednesday in the month or October 31, 2016 which is the 5th Monday in October. How can I find which number the particular occurrence of a day is in the month?
Use the get method of the Calendar class.
public static int getOccurenceOfDayInMonth() {
return Calendar.getInstance().get(Calendar.DAY_OF_WEEK_IN_MONTH);
}
[EDIT]
Here is a solution given any date, rather than the current date.
public static int getOccurenceOfDayInMonth(Date date) {
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
return calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH);
}
I have this object Date in this format : 2014-05-20 18:17:26.337
I try to do this:
Calendar c = Calendar.getInstance();
c.setTime(myDate);
int dayOfWeek = c.get(Calendar.DAY_OF_WEEK);
int dayOfMonth = c.get(Calendar.DAY_OF_MONTH);
int Month = c.get(Calendar.MONTH);
int year = c.get(Calendar.YEAR);
But the information are wrong..
How I can resolve it?
This is the expected value, please read the javadoc carefully:
http://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html#MONTH
For Month:
Field number for get and set indicating the month. This is a calendar-specific value. The first month of the year in the Gregorian and Julian calendars is JANUARY which is 0; the last depends on the number of months in a year.
For day of week:
public static final int DAY_OF_WEEK
Field number for get and set indicating the day of the week. This field takes values SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, and SATURDAY.
From java doc:
Blockquote
int java.util.Calendar.MONTH = 2 [0x2]
Field number for get and set indicating the month. This is a
calendar-specific value. The first month of the year in the Gregorian
and Julian calendars is JANUARY which is 0; the last depends on the
number of months in a year.
See Also: JANUARY FEBRUARY MARCH APRIL MAY JUNE JULY AUGUST SEPTEMBER
OCTOBER NOVEMBER DECEMBER UNDECIMBER
You need to read Java doc first
Field number for get and set indicating the month. This is a
calendar-specific value. The first month of the year in the Gregorian
and Julian calendars is JANUARY which is 0; the last depends on the
number of months in a year.
So you will get month as 4
int month = c.get(Calendar.MONTH);
Date fakeDate = sdf.parse("15/07/2013 11:00 AM");
Calendar calendar = Calendar.getInstance()
calendar.setTime(fakeDate);
int currentMonth = calendar.get(Calendar.MONTH);
I get currentMonth == 6 instead of 7.
why is that?
Because Calendar.MONTH is ZERO based. Why?
Check the docs: (always)
Field number for get and set indicating the month. This is a
calendar-specific value. The first month of the year in the Gregorian
and Julian calendars is JANUARY which is 0; the last depends on the
number of months in a year.
As the doc says - Field number for get and set indicating the month. This is a calendar-specific value. The first month of the year in the Gregorian and Julian calendars is JANUARY which is 0; the last depends on the number of months in a year.
So try something like this
int currentMonth = calendar.get(Calendar.MONTH)+1;
Because
calendar.get(Calendar.MONTH) shall give you (currentMonthValue-1) as the value of january starts with 0
It should be
int currentMonth = calendar.get(Calendar.MONTH)+1;
I've read around and basically I've figured out that the Calendar object is capable of adding 1 month to a date specified by using something like:
Calendar cal = Calendar.getInstance();
cal.add(Calendar.MONTH, 1);
Although I don't like its behavior whenever the date is on either the 30 or 31. If ever I add 1 month to 01/31/2012, the output becomes 02/29/2012. When I add 1 more month, it becomes 03/29/2012.
Is there anyway I can force 02/29/2012 to become 03/01/2012 automatically?
Basically this is what I want to happen:
Default date: 01/31/2012
Add 1 month: 03/01/2012
Add 1 more month: 03/31/2012
What you are asking for is some implicit knowledge that if the starting date is the last day of the month, and you add 1 month, the result should be the last day of the following month. I.e. the property "last-day-of-month" should be sticky.
This is not directly available in Java's Calendar, but one possible solution is to use Calendar.getActualMaximum(Calendar.DAY_OF_MONTH) to reset the day after incrementing the month.
Calendar cal = ...;
cal.add(Calendar.MONTH,1);
cal.set(Calendar.DAY_OF_MONTH,cal.getActualMaximum(Calendar.DAY_OF_MONTH));
You could even subclass GregorianCalendar and add a method
public Calendar endOfNextMonth() { ... }
to encapsulate the operation.
Well for add 30 days you can do something like this:
public static java.sql.Date sumarFechasDias(java.sql.Date fch, int days) {
Calendar cal = new GregorianCalendar();
cal.setTimeInMillis(fch.getTime());
cal.add(Calendar.DATE, days);
return new java.sql.Date(cal.getTimeInMillis());
}
if days=30, it will return your date with 30 days added.
It looks like you want the calendar to roll up to the beginning of the next month if the date of the next month is smaller than the date of the month before it. Here's how we'd do that:
Calendar cal = Calendar.getInstance();
int oldDay = cal.get(DAY_OF_MONTH);
cal.add(Calendar.MONTH, 1);
// If the old DAY_OF_MONTH was larger than our new one, then
// roll over to the beginning of the next month.
if(oldDay > cal.get(DAY_OF_MONTH){
cal.add(Calendar.MONTH, 1);
cal.set(Calendar.DAY, 1);
}