Using Calendar I can get the week, year and all details for the current day. How can I navigate to a particualr day in that week?
Say, calendar.get(Calendar.DAY_OF_WEEK); returns 3, which means a Tuesday. Now, I want to go to say Friday for that week or any other day in that week. How can I do that?
Thanks for your replies. I think I need to make the scenario more clear.
Basically, I am trying to disable email alerts in my system during specified period.
I get values like:
disableStart = "FRIDAY-19:00"
disableEnd = "SUNDAY-19:00"
Now, i need to verify if email should be sent at a particular time.
e.g. if today = Thursday any time, send email
but, if today = Saturday any time can't send as per values above.
If I understand correctly you can use the Calendar.set(Field, value) method.
SimpleDateFormat f = new SimpleDateFormat("dd-MM-yyyy");
Calendar c = Calendar.getInstance();
System.out.println(c.get(Calendar.DAY_OF_WEEK));
System.out.println(f.format(c.getTime()));
c.set(Calendar.DAY_OF_WEEK, Calendar.TUESDAY);
System.out.println(c.get(Calendar.DAY_OF_WEEK));
System.out.println(f.format(c.getTime()));
Produces the output
6
08-10-2010
3
05-10-2010
Calendar c = Calendar.getInstance();
Date date = new Date();
c.setTime(date);
System.out.println("Today: " + c.getTime());
c.setTime(date);
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println("MONDAY: " + c.getTime());
c.setTime(date);
c.set(Calendar.DAY_OF_WEEK, Calendar.TUESDAY);
System.out.println("TUESDAY: " + c.getTime());
c.setTime(date);
c.set(Calendar.DAY_OF_WEEK, Calendar.WEDNESDAY);
System.out.println("WEDNESDAY: " + c.getTime());
c.setTime(date);
c.set(Calendar.DAY_OF_WEEK, Calendar.THURSDAY);
System.out.println("THURSDAY: " + c.getTime());
c.setTime(date);
c.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
System.out.println("FRIDAY: " + c.getTime());
c.setTime(date);
c.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY);
System.out.println("SATURDAY: " + c.getTime());
c.setTime(date);
c.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
System.out.println("SUNDAY: " + c.getTime());
Gives:
Today: Fri Oct 08 15:45:14 CEST 2010
MONDAY: Mon Oct 04 15:45:14 CEST 2010
TUESDAY: Tue Oct 05 15:45:14 CEST 2010
WEDNESDAY: Wed Oct 06 15:45:14 CEST 2010
THURSDAY: Thu Oct 07 15:45:14 CEST 2010
FRIDAY: Fri Oct 08 15:45:14 CEST 2010
SATURDAY: Sat Oct 09 15:45:14 CEST 2010
SUNDAY: Sun Oct 10 15:45:14 CEST 2010
Which seams to mean that, at least on my system, the weeks starts on monday.
cal.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
Thanks to Kevin and Maurice for the answers. They really gave me the start point.
I ended with this test code, in case it helps anyone.
private static Date getTimeForAnyDayInWeek(int nDay, int nHour, int nMin)
{
Calendar c = Calendar.getInstance();
c.setFirstDayOfWeek(Calendar.MONDAY);
Date date = Calendar.getInstance().getTime();
c.setTime(date);
c.set(Calendar.DAY_OF_WEEK, nDay);
c.set(Calendar.HOUR_OF_DAY, nHour);
c.set(Calendar.MINUTE, nMin);
return c.getTime();
}
public static void main(String[] args)
{
Date start = getTimeForAnyDayInWeek(6, 19, 00);
Date end = getTimeForAnyDayInWeek(8, 19, 00);
Date c = new Date();
if (start.before(c) && c.before(end))
System.out.println("BLOCK");
else
System.out.println("SEND");
}
Thanks,
Anubhav
This is a perfect example of why jodatime is so good, here is my similar code
DateTime dt = new DateTime(); //current datetime, jodatime format
DateTime fridayLastWeek = dt.minusWeeks(1).dayOfWeek().setCopy("Friday");
Date convertedtorubbishdateformat = fridayLastWeek.toDate();
I used to waste so much time witht he standard java date/calendar. Then i got jodatime, you wont regret, it apparently will be used as part of standard java in the future. I didn;t bother downlaoding the jar for for ages, I wish I had done, you won't regret it.
Related
Hi can any one explain why such abnormal behavior from Calendar .after method
Calendar cal = Calendar.getInstance();
Calendar cal1 = Calendar.getInstance();
cal.set(Calendar.HOUR, 14);
cal1.set(Calendar.HOUR, 13);
System.out.println(cal.after(cal1)+" Cal "+cal.getTime()+" cal1 "+cal1.getTime());
cal.set(Calendar.DATE, Calendar.getInstance().get(Calendar.DATE));
System.out.println(cal.after(cal1)+" Cal "+cal.getTime()+" cal1 "+cal1.getTime());
Output:
true Cal Tue Oct 01 02:55:16 IST 2019 cal1 Tue Oct 01 01:55:16 IST 2019
true Cal Wed Oct 30 02:55:16 IST 2019 cal1 Tue Oct 01 01:55:16 IST 2019
but I did not get why cal is after cal1 even if i have set cal1's date to current date,
so if cal is today, I assigned the time as 14 hr it mover to next date then i set the date as current date in cal while for cal1 i did not.
So why still cal.after(cal1) is showing true in second syso while my cal1 is clearly 1 day greater than cal?
any suggestion to resolve such problem? Use java.time
I agree with you that there are some surprises in your code. You may have intended this:
ZoneId zone = ZoneId.of("Asia/Kolkata");
ZonedDateTime zdt = ZonedDateTime.now(zone);
ZonedDateTime zdt1 = ZonedDateTime.now(zone);
zdt = zdt.withHour(14);
zdt1 = zdt1.withHour(13);
System.out.println(zdt.isAfter(zdt1) + " zdt " + zdt + " zdt1 " + zdt1);
zdt = zdt.withDayOfMonth(ZonedDateTime.now(zone).getDayOfMonth());
System.out.println(zdt.isAfter(zdt1) + " zdt " + zdt + " zdt1 " + zdt1);
Output when I ran the code just now:
true zdt 2019-09-30T14:44:13.630029+05:30[Asia/Kolkata] zdt1 2019-09-30T13:44:13.630362+05:30[Asia/Kolkata]
true zdt 2019-09-30T14:44:13.630029+05:30[Asia/Kolkata] zdt1 2019-09-30T13:44:13.630362+05:30[Asia/Kolkata]
I get true both times just as you got from your code, which shouldn’t be surprising. As others have said, 02:55h is after 01:55h, and Oct 30 is after Oct 01. Also, referring to my result, 14:44 is after 13:44. In both lines these two times are compared.
I am using java.time, the modern Java date and time API.
What went wrong in your code?
The surprises in your code stem from the Calendar class being poorly designed and often behaving differently from what we would immediately expect.
Why when you set the hour to 14, you get Tue Oct 01 02:55:16 IST 2019? The date has changed into the following month, and the hour of day is 2, not 14.
Why when you set the date to today’s date, September 30, you get October 30?
For 1., Calendar.HOUR refers to hour within AM or PM from 0 through 11. So setting it to 14 we should have expected an exception. A Calendar with standard settings doesn’t care. Since the time was already in PM, it extrapolates, so 14 PM becomes 2 AM on the next day. Since today is the last day of September, you get October 1.
For 2., Calendar.DATE doesn’t refer to the full date, but to the day of month. Since current day of month is 30 and we already had October1, we get October 30.
Long story short: Avoid the Calendar class. Use ZonedDateTime and/or other classes form java.time, the modern Java date and time API. They are so much nicer to work with and give far fewer surprises like the ones you experienced.
Link
Oracle tutorial: Date Time explaining how to use java.time.
Java docs for - Calendar.after()
public boolean after(Object when) {
return when instanceof Calendar && compareTo((Calendar)when) > 0;
}
//By definition :- true if the time of this Calendar is after the time represented by when; false otherwise.
System.out.println(cal.after(cal1)+" Cal "+cal.getTime()+" cal1 "+cal1.getTime());
//true Cal Tue Oct 01 02:17:46 IST 2019 cal1 Tue Oct 01 01:17:46 IST 2019
cal.set(Calendar.HOUR, 13);
cal1.set(Calendar.HOUR, 14);
System.out.println(cal.after(cal1)+" Cal "+cal.getTime()+" cal1 "+cal1.getTime());
//false Cal Tue Oct 01 01:16:55 IST 2019 cal1 Tue Oct 01 02:16:55 IST 2019
cal.set(Calendar.DATE, Calendar.getInstance().get(Calendar.DATE));
System.out.println(cal.after(cal1)+" Cal "+cal.getTime()+" cal1 "+cal1.getTime());
//true Cal Wed Oct 30 13:17:46 IST 2019 cal1 Tue Oct 01 14:17:46 IST 2019
System.out.println(cal.after(cal1)+" Cal "+cal.getTime()+" cal1 "+cal1.getTime());
//true Cal Tue Oct 01 02:25:19 MMT 2019 cal1 Tue Oct 01 01:25:19 MMT 2019
cal.set(Calendar.DATE, Calendar.getInstance().get(Calendar.DATE));
System.out.println(cal1.after(cal)+" Cal "+cal.getTime()+" cal1 "+cal1.getTime());
//false Cal Wed Oct 30 02:25:19 MMT 2019 cal1 Tue Oct 01 01:25:19 MMT 2019
Using
cal.setTime((Calendar.getInstance()).getTime());
instead of
cal.set(Calendar.DATE, Calendar.getInstance().get(Calendar.DATE));
gives the desired result.
From the below java code I'm getting a month First & last dateTimestamp, but here i need last dateTimestamp as - "Mon Aug 31 23:59:59 IST 2015" instead of - "Mon Aug 31 00:00:00 IST 2015"?
Calendar cal = Calendar.getInstance();
int year = 2015;
int month = 07;
cal.set(cal.DATE,1);
cal.set(cal.YEAR,year);
cal.set(cal.MONTH, month);
String firstDate = (cal.getActualMinimum(cal.DATE) + "/" + (month+1) + "/" +year);
System.out.println("firstDate-->"+"\t"+firstDate);
String lastDate = (cal.getActualMaximum(cal.DATE) + "/" + (month+1) + "/" +year);
System.out.println("lastDate-->"+"\t"+lastDate);
DateFormat firstFormat = new SimpleDateFormat("dd/MM/yyyy");
Date beginDate = firstFormat.parse(firstDate);
System.out.println("BeginDate Timestamp"+ "\t" + beginDate);
DateFormat secoundFormat = new SimpleDateFormat("dd/MM/yyyy");
Date endDate = secoundFormat.parse(lastDate);
System.out.println("endDate Timestamp"+ "\t" + endDate);
Output:->
firstDate--> 1/8/2015
lastDate--> 31/8/2015
BeginDate Timestamp Sat Aug 01 00:00:00 IST 2015
endDate Timestamp Mon Aug 31 00:00:00 IST 2015
Please help me if we have any solution.
If I understand your question, it looks as if you want to pass a year and month into a method, and get back the last day of the passed month.
I would suggest consider (in this order):
which jdk you use
configuration of calendar
configuration of timezone (maybe)
using jodatime
As of 1.8 many JodaTime-like features have been added to the jdk- e.g. see https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html (If you arent using 1.8 you can use the joda lib, assuming your organization allows it)
Calendar.getInstance() gives a default TimeZone and a default Locale, which means the definitions of the running JVM. You may or may not need to consider this and implement more than just getInstance(). See API javadoc.
Assuming a Gregeorian Calendar (hey, you could be Bahaian and have 19 months in the year ...) , here is one partial implementation using JDK 1.7, JodaTime jar 2.2, validation-1.0.0.GA jar:
#Test
public void testDate() {
final String dateStringOfFirstDay = "1.7.2015";
final Date lastDayOfMonth = getLastDayOfMonth(dateStringOfFirstDay);
Assert.assertNotNull(lastDayOfMonth);
//more assertions ...
}
private Date getLastDayOfMonth(#NotNull String dateStringOfFirstDay) {
//further validation here necessary according to required date format
DateTime dt = DateTime.parse(dateStringOfFirstDay);
return dt.dayOfMonth().withMaximumValue().toDate();
}
The defintion of DateFormat/DateTimeFormat and further result assertions is left up to you.
Best of luck!
Guys I got a solution for my question!!!
I think it will help u too...
Calendar calendar = Calendar.getInstance();
int year=2015;
int month=7;
int date=31;
int hourOfDay=23;
int minute=59;
int second=59;
int milliSecond=999;
calendar.set(year, month, date, hourOfDay, minute, second);
calendar.set(calendar.MILLISECOND, milliSecond);
System.out.println("Time from Calendar: "+calendar.getTime());
long timeInMilliSeconds=calendar.getTimeInMillis();
System.out.println("timeInMilliSeconds from calendar: "+timeInMilliSeconds);
Timestamp timestamp=new Timestamp(timeInMilliSeconds);
System.out.println(timestamp);
The above program gives the last date last timestamp in a selected month.
getTimeInMillis() takes the time from Jan 01, 1970 to current time in Milliseconds.
Using those milliseconds i'm getting the Timestamp.
Thank you for your help guys!!!
OutPut:->
Time from Calendar: Mon Aug 31 23:59:59 IST 2015
timeInMilliSeconds from calendar: 1441045799999
2015-08-31 23:59:59.999
I have a simple for my problem:
TimeZone fromTimeZone = TimeZone.getTimeZone("America/Santiago");
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY, 8);
calendar.set(Calendar.MINUTE, 45);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
System.out.println(calendar.getTime() + " |Mili: " + calendar.getTimeInMillis());
The output: (My timezone is ICT)
Wed Apr 01 19:45:00 ICT 2015 |Milisecond: 1427892300000
The problem is: The calendar return wrong time for this Timezone on DST day. The timezone "America/Santiago" should be UTC-3 for now (ref: http://www.timeanddate.com/worldclock/chile/santiago.) . It need to show:
Wed Apr 01 18:45:00 ICT 2015 |Milisecond: 1427888700000
You have not applied the timezone fromTimeZone to the calendar .
I have tried the following; but the results are disappointing.
I want to increment the the months.
String dStartTime="2012-03-01";
SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy-MM-DD");
Date dateStartTime = dateFormatter.parse(dStartTime);
Calendar cal = Calendar.getInstance();
cal.setTime(dateStartTime);
cal.add(Calendar.MONTH, 1);
System.out.println(cal.getTime());
System.out.println(dateFormatter.format(cal.getTime()));
OUTPUT
Wed Feb 01 00:00:00 IST 2012 --- This is correct
2012-02-32 --- This is wrong. I want the Day should be one.
Please let me know what is the problem here?
Change new SimpleDateFormat("yyyy-MM-DD") to new SimpleDateFormat("yyyy-MM-dd").
DD is "Day in year" but you need dd "Day in month".
See http://docs.oracle.com/javase/6/docs/api/java/text/SimpleDateFormat.html for Date and Time Patterns.
I've below code in Java 1.7:
DateFormat df = DateFormat.getInstance();
Date startDate = df.parse("07/28/12 01:00 AM, PST");
The above date time (07/28/12 01:00 AM, PST) is in the properties file which is configurable. If this date time is already passed, then I need to get the current date, set the time part from above string which is 01:00 AM PST in the current date & if this time is also already passed, then get the next day & set the time part from above string in it. The final object should be Date since I need to use it in Timer object.
How can I do this efficiently? Should I convert from date to Calendar or vice-versa? Can any one provide snippet?
You should look into the Calendar class. You can use constructs like:
Calendar cal = Calendar.getInstance();
cal.setTime(startDate);
cal.add(Calendar.DAY_OF_YEAR, 1);
It also has methods for checking if your startDate is before() or after() a new date (use the current time).
While writing of the built-in Java date/time structure, i would be remiss if i didnt plug Joda Time, considered by many to be superior to the native Java implementation.
EDIT:
It would be more efficient to show an example of the Date.compareTo() process, as the Calendar.before() and Calendar.after() require comparisons against other Calendar objects, which can be expensive to create.
take a look at the following:
DateFormat df = DateFormat.getInstance();
Date startDate = df.parse("07/28/12 01:00 AM, PST");
Calendar cal = Calendar.getInstance();
cal.setTime(startDate);
Date now = new Date();
if (startDate.compareTo(now)< 0) {
System.out.println("start date: " + startDate + " is before " + now);
Calendar nowCal = Calendar.getInstance();
nowCal.add(Calendar.DAY_OF_YEAR,1);
cal.set(Calendar.DAY_OF_YEAR, nowCal.get(Calendar.DAY_OF_YEAR));
} else if (startDate.compareTo(now) == 0) {
System.out.println("startDate: " +startDate + " is equal to " + now);
} else {
System.out.println("startDate: " + cal + " is after " + now);
}
System.out.println(cal.getTime());
I think this should work...your algorthim has my head spinning a little and I'm in a different time zone, so you original string didn't work :P
try {
DateFormat df = DateFormat.getInstance();
Date startDate = df.parse("28/07/2012 01:00 AM");
System.out.println("StartDate = " + startDate);
Date callDate = startDate;
Calendar today = Calendar.getInstance();
Calendar start = Calendar.getInstance();
start.setTime(startDate);
System.out.println("Today = " + today.getTime());
// If this date time is already passed
// Tue Jul 31 12:18:09 EST 2012 is after Sat Jul 28 01:00:00 EST 2012
if (today.after(start)) {
//then I need to get the current date, set the time part from above string in the current date
Calendar timeMatch = Calendar.getInstance();
timeMatch.setTime(startDate);
timeMatch.set(Calendar.DATE, today.get(Calendar.DATE));
timeMatch.set(Calendar.MONTH, today.get(Calendar.MONTH));
timeMatch.set(Calendar.YEAR, today.get(Calendar.YEAR));
//& if this time is also already passed, then get the next day & set the time part from above string in it
if (timeMatch.after(today)) {
timeMatch.add(Calendar.DATE, 1);
}
callDate = timeMatch.getTime();
}
System.out.println("CallDate = " + callDate);
} catch (ParseException exp) {
exp.printStackTrace();
}
This produces the following output
StartDate = Sat Jul 28 01:00:00 EST 2012
Today = Tue Jul 31 12:18:09 EST 2012
CallDate = Tue Jul 31 01:00:00 EST 2012