I have the following code in groovy to get current time in hours.
def now = new Date()
def time = now.getHours()
but the getHour() method is deprecated. What are the disadvantages if I use this method and the what is the alternative to this method in groovy/Java ?
Use Calendar,
Calendar cal=Calendar.getInstance();//it return same time as new Date()
def hour = cal.get(Calendar.HOUR_OF_DAY)
For details, read this docs.
Try using Joda Time instead of standard java.util.Date classes. Joda Time library has much better API for handling dates.
DateTime dt = new DateTime(); // current time
int month = dt.getMonth(); // gets the current month
int hours = dt.getHourOfDay(); // gets hour of day
You can use the traditional classes like this to fetch fields from given Date instance.
Date date = new Date(); // given date
Calendar calendar = GregorianCalendar.getInstance(); // creates a new calendar instance
calendar.setTime(date); // assigns calendar to given date
calendar.get(Calendar.HOUR_OF_DAY); // gets hour in 24h format
calendar.get(Calendar.HOUR); // gets hour in 12h format
calendar.get(Calendar.MONTH); // gets month number, NOTE this is zero based!
You can use Joda-time for get current time or getHours
Related
I get a string in the format yyyy-MM-dd HH:mm which represents a Date and Time in UTC.
Next step is to put this into a Calendar (with TimeZone UTC).
In addition need to also create a separate Calendar which has converted the UTC to "Europe/London" timeZone (GMT/BST).
After that I need to be able to detect if the "Europe/London" calendar has a DST (Day Light Savings Offset).
The code below will show you how far I have got and it runs ok on a UK based computer whose default System Timezone is GMT. However when I run it on a pc whose timezone is UTC it fails. It seems to not be able to tell me if there is an DST_offset (its always zero).
Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
cal.set(Calendar.YEAR, 2016);
cal.set(Calendar.MONTH, 1);
cal.set(Calendar.DAY_OF_MONTH, 27);
cal.set(Calendar.HOUR_OF_DAY, 23);
cal.set(Calendar.MINUTE, 35);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
//This is required as Java Date JAN starts at 0.
int MonthCon = cal.get(Calendar.MONTH)-1;
cal.set(Calendar.MONTH, MonthCon);
Date d = cal.getTime();
SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssz");
f.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println("UTC: " + f.format(d));
f.setTimeZone(TimeZone.getTimeZone("Europe/London"));
System.out.println("BST: " + f.format(d));
//Creates a BST calendar of the same UTC time
String dateStrBST = f.format(d);
SimpleDateFormat curFormater = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssz");
curFormater.setTimeZone(TimeZone.getTimeZone("Europe/London"));
Date dateObjBST = curFormater.parse(dateStrBST);
System.out.println("BSTNewDate: " + f.format(dateObjBST));
Calendar calBST = Calendar.getInstance(TimeZone.getTimeZone("BST"));
calBST.setTime(dateObjBST);
System.out.println("Current TimeZone is : " + calBST.getTimeZone());
int offset = calBST.get(Calendar.DST_OFFSET);
System.out.println("Day Light Savings: "+offset);
System.out.println("Transition Day: "+isDSTTransitionDay(cal.get(Calendar.YEAR),cal.get(Calendar.MONTH),cal.get(Calendar.DAY_OF_MONTH))+" Transition Type: "+DSTtransitionType(cal.get(Calendar.YEAR),cal.get(Calendar.MONTH),cal.get(Calendar.DAY_OF_MONTH)));
Unfortunately I need to be able to detect if any particular day is a transition day, that is to say a day that changes from DST on/off or off/on. Again this works on the local computer but not on the UTC timezone one.
private static boolean isDSTTransitionDay(int year, int month, int day) throws ParseException
{
Calendar calStartofDay = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calStartofDay.set(Calendar.YEAR, year);
calStartofDay.set(Calendar.MONTH, month);
calStartofDay.set(Calendar.DAY_OF_MONTH, day);
calStartofDay.set(Calendar.HOUR_OF_DAY, 00);
calStartofDay.set(Calendar.MINUTE, 0);
calStartofDay.set(Calendar.SECOND, 1);
Date dStartofDay = calStartofDay.getTime();
SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssz");
f.setTimeZone(TimeZone.getTimeZone("Europe/London"));
String dateStrUTCtoBST = f.format(dStartofDay);
SimpleDateFormat curFormater = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssz");
curFormater.setTimeZone(TimeZone.getTimeZone("Europe/London"));
Date dateObjBST = curFormater.parse(dateStrUTCtoBST);
Calendar calBST = Calendar.getInstance();
calBST.setTime(dateObjBST);
int offsetStart = calBST.get(Calendar.DST_OFFSET);
calBST.add(Calendar.HOUR_OF_DAY, 23);
int offsetEnd = calBST.get(Calendar.DST_OFFSET);
//System.out.println("Start: "+offsetStart+" End: "+offsetEnd);
if (offsetEnd == offsetStart)
{
return false;
}else
{
//if(offsetStart<offsetEnd) {System.out.println("Transition to BST");}else{System.out.println("Transition to UTC/GMT");};
return true;
}
}
So on the UTC computer it fails miserably as it always puts Calendar.DST_OFFSET at zero. I have clearly misunderstood something along the way so any help/clarity would be good.
I pretty much have to keep Calendars as the rest of the code uses it but I realise the Java8 has many more fancy ways to do things.
Please allow me to be honest, I tried to read your code and didn’t really understand your way of trying to obtain what you want. If you can use Java 8, I recommend switching to using the Java 8 date and time classes. With these your job isn’t very complicated. For the demonstration I have chosen last October 30, the date when Britain (and EU) changed back from summer time (daylight saving time) to standard time.
String originalDate = "2016-10-30 23:35";
LocalDateTime localTime = LocalDateTime.parse(originalDate, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm"));
ZonedDateTime utcTime = localTime.atZone(ZoneOffset.UTC);
ZonedDateTime bstTime = utcTime.withZoneSameInstant(ZoneId.of("Europe/London"));
// the summer time offset is how many milliseconds?
long dstOffset = ChronoUnit.MILLIS.between(utcTime.toLocalDateTime(), bstTime.toLocalDateTime());
System.out.println(dstOffset); // prints 0
// try the same at start of day (midnight)
utcTime = utcTime.toLocalDate().atStartOfDay(ZoneOffset.UTC);
bstTime = utcTime.withZoneSameInstant(ZoneId.of("Europe/London"));
dstOffset = ChronoUnit.MILLIS.between(utcTime.toLocalDateTime(), bstTime.toLocalDateTime());
System.out.println(dstOffset); // prints 3600000
// and next midnight
utcTime = utcTime.plusDays(1);
bstTime = utcTime.withZoneSameInstant(ZoneId.of("Europe/London"));
dstOffset = ChronoUnit.MILLIS.between(utcTime.toLocalDateTime(), bstTime.toLocalDateTime());
System.out.println(dstOffset); // prints 0
You are using
Calendar calBST = Calendar.getInstance();
That sets calBST to the computer's timezone (on the UTC computer, it will be UTC).
calBST.setTime(dateObjBST); sets the time, not the timezone.
Try using getInstance(TimeZone zone) there also.
In any case, I would replace your code like this:
Calendar calStartofDay = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calStartofDay.set(Calendar.YEAR, 2017);
calStartofDay.set(Calendar.MONTH, 0);
calStartofDay.set(Calendar.DAY_OF_MONTH, 21);
calStartofDay.set(Calendar.HOUR_OF_DAY, 00);
calStartofDay.set(Calendar.MINUTE, 0);
calStartofDay.set(Calendar.SECOND, 1);
Calendar calBST = Calendar.getInstance(TimeZone.getTimeZone("Europe/London"));
calBST.setTimeInMillis(calStartofDay.getTimeInMillis());
// use this to check the time
System.out.printf("%tc%n", calBST);
Also, from the Calendar docs, be careful about this:
set(f, value) changes calendar field f to value. In addition, it sets
an internal member variable to indicate that calendar field f has been
changed. Although calendar field f is changed immediately, the
calendar's time value in milliseconds is not recomputed until the next
call to get(), getTime(), getTimeInMillis(), add(), or roll() is made.
Thus, multiple calls to set() do not trigger multiple, unnecessary
computations. As a result of changing a calendar field using set(),
other calendar fields may also change, depending on the calendar
field, the calendar field value, and the calendar system. In addition,
get(f) will not necessarily return value set by the call to the set
method after the calendar fields have been recomputed. The specifics
are determined by the concrete calendar class.
I am having issues with the calculation of when the next Last Day of the Month is for a notification which is scheduled to be sent.
Here is my code:
RecurrenceFrequency recurrenceFrequency = notification.getRecurrenceFrequency();
Calendar nextNotifTime = Calendar.getInstance();
This is the line causing issues I believe:
nextNotifTime.add(recurrenceFrequency.getRecurrencePeriod(),
recurrenceFrequency.getRecurrenceOffset());
How can I use the Calendar to properly set the last day of the next month for the notification?
Calendar.getInstance().getActualMaximum(Calendar.DAY_OF_MONTH);
This returns actual maximum for current month. For example it is February of leap year now, so it returns 29 as int.
java.time.temporal.TemporalAdjusters.lastDayOfMonth()
Using the java.time library built into Java 8, you can use the TemporalAdjuster interface. We find an implementation ready for use in the TemporalAdjusters utility class: lastDayOfMonth.
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;
LocalDate now = LocalDate.now(); //2015-11-23
LocalDate lastDay = now.with(TemporalAdjusters.lastDayOfMonth()); //2015-11-30
If you need to add time information, you may use any available LocalDate to LocalDateTime conversion like
lastDay.atStartOfDay(); //2015-11-30T00:00
And to get last day as Date object:
Calendar cal = Calendar.getInstance();
cal.set(Calendar.DATE, cal.getActualMaximum(Calendar.DATE));
Date lastDayOfMonth = cal.getTime();
You can set the calendar to the first of next month and then subtract a day.
Calendar nextNotifTime = Calendar.getInstance();
nextNotifTime.add(Calendar.MONTH, 1);
nextNotifTime.set(Calendar.DATE, 1);
nextNotifTime.add(Calendar.DATE, -1);
After running this code nextNotifTime will be set to the last day of the current month. Keep in mind if today is the last day of the month the net effect of this code is that the Calendar object remains unchanged.
Following will always give proper results:
Calendar cal = Calendar.getInstance();
cal.set(Calendar.MONTH, ANY_MONTH);
cal.set(Calendar.YEAR, ANY_YEAR);
cal.set(Calendar.DAY_OF_MONTH, 1);// This is necessary to get proper results
cal.set(Calendar.DATE, cal.getActualMaximum(Calendar.DATE));
cal.getTime();
You can also use YearMonth.
Like:
YearMonth.of(2019,7).atEndOfMonth()
YearMonth.of(2019,7).atDay(1)
See
https://docs.oracle.com/javase/8/docs/api/java/time/YearMonth.html#atEndOfMonth--
Using the latest java.time library here is the best solution:
LocalDate date = LocalDate.now();
LocalDate endOfMonth = date.with(TemporalAdjusters.lastDayOfMonth());
Alternatively, you can do:
LocalDate endOfMonth = date.withDayOfMonth(date.lengthOfMonth());
Look at the getActualMaximum(int field) method of the Calendar object.
If you set your Calendar object to be in the month for which you are seeking the last date, then getActualMaximum(Calendar.DAY_OF_MONTH) will give you the last day.
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
Date date = sdf.parse("11/02/2016");
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
System.out.println("First Day Of Month : " + calendar.getActualMinimum(Calendar.DAY_OF_MONTH));
System.out.println("Last Day of Month : " + calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
Kotlin date extension implementation using java.util.Calendar
fun Date.toEndOfMonth(): Date {
return Calendar.getInstance().apply {
time = this#toEndOfMonth
}.toEndOfMonth().time
}
fun Calendar.toEndOfMonth(): Calendar {
set(Calendar.DAY_OF_MONTH, getActualMaximum(Calendar.DAY_OF_MONTH))
return this
}
You can call toEndOfMonth function on each Date object like Date().toEndOfMonth()
Probably there will be simply and fast answer but I still cant find out why is the result of
Date date = new Date(60000); //one min.
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
String dateStr = dateFormat.format(date);
dateStr - 01:01:00
Still one hour more. Time zone? How can I set it without it? Thanks.
Date represents a specific moment in time, not a duration. new Date(60000) does not create "one minute". See the docs for that constructor:
Initializes this Date instance using the specified millisecond value. The value is the number of milliseconds since Jan. 1, 1970 GMT.
If you want "one minute from now" you'll probably want to use the Calendar class instead, specifically the add method.
Update:
DateUtils has some useful methods that you might find useful. If you want the elapsed time in HH:mm:ss format, you might try DateUtils.formatElapsedTime. Something like:
String dateStr = DateUtils.formatElapsedTime(60);
Note that the 60 is in seconds.
Three ways to use java.util.Date to specify one minute:
1. Using SimpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC")) as shahtapa said:
Date date = new Date(60*1000); //one min.
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
2. Using java.util.Calendar as kabuko said:
Calendar calendar = Calendar.getInstance();
calendar.clear();
calendar.set(Calendar.MINUTE,1); //one min.
Date date = calendar.getTime();
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
Other calendar.set() statements can also be used:
calendar.set(Calendar.MILLISECOND,60*1000); //one min.
calendar.set(1970,0,1,0,1,0); //one min.
3. Using these setTimeZone and Calendar ideas and forcing Calendar to
UTC Time-Zone
as Simon Nickerson said:
Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calendar.clear();
calendar.set(Calendar.MINUTE,1); //one min.
Date date = calendar.getTime();
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
Note: I had a similar issue: Date 1970-01-01 was in my case -3 600 000 milliseconds (1 hour late) java.util.Date(70,0,1).getTime() -> -3600000
I recommend to use TimeUnit
"A TimeUnit represents time durations at a given unit of granularity and provides utility methods to convert across units, and to perform timing and delay operations in these units. A TimeUnit does not maintain time information, but only helps organize and use time representations that may be maintained separately across various contexts. A nanosecond is defined as one thousandth of a microsecond, a microsecond as one thousandth of a millisecond, a millisecond as one thousandth of a second, a minute as sixty seconds, an hour as sixty minutes, and a day as twenty four hours."
http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/TimeUnit.html
Date date = new Date(); // getting actual date
date = new Date (d.getTime() + TimeUnit.MINUTES.toMillis(1)); // adding one minute to the date
i am using a reporting tools which only support one line expression
By example I want to get the Date of yesterday
the class Calendar has a add method, but it returns void so
Calendar.getInstance().add(Calendar.DAY_OF_MONTH,-1).getTime()
didn't work
don't know how to get this done
Thanks
Use Joda-Time:
new org.joda.time.DateTime().minusDays(1).toDate();
If it really has to be a one-liner and it doesn't matter if the code is understandable, I think the following statement should work:
Date yesterday = new SimpleDateFormat("yyyyMMdd").parse(
""+(Integer.parseInt(new SimpleDateFormat("yyyyMMdd").format(new Date()))-1));
It formats the current date as "yyyyMMdd", e.g. "20100812" for today, parses it as an int: 20100812, subtracts one: 20100811, and then parses the date "20100811" using the previous format. It will also work if today is the first of a month, since the 0th of a month is parsed by a lenient DateFormat as the last day of the previous month.
The format "yyyyDDD" ought to work as well (D being day of year).
For the first day of the current month, you can use a similar trick:
Date firstday = new SimpleDateFormat("yyyyMMdd").parse(
new SimpleDateFormat("yyyyMM").format(new Date())+"01");
Can't you do something like
new Date( new Date().getTime() - 86400000 );
to get the current time, subtract the # of milliseconds in a day, and build a new date object from that?
Assuming you want a java.util.Date object (since you used getTime() in your question and that returns a java.util.Date), you could do:
// Get yesterday's date. System.currentTimeMillis() returns the
// number of milliseconds between the epoch and today, and the
// 86400000 is the number of milliseconds in a day.
new Date(System.currentTimeMillis() - 86400000);
Oops, didn't see your first day of the month query before. I came up with the following to get that using util.Date, but I think this is about the time you want to switch to using Joda or Calendar... (dear SO, please don't vote me down for the horrendousness of the following...)
// This will return the day of the week as an integer, 0 to 6.
new Date(System.currentTimeMillis() - ((new Date().getDate()-1) * 86400000)).getDay();
This should be done as follows:
Calendar cal = Calendar.getInstance();
cal .add(Calendar.DAY_OF_MONTH,-1);
cal .getTime();
When you are doing this:
Calendar.getInstance().add(Calendar.DAY_OF_MONTH,-1).getTime()
You are essentially asking a method (add()) that returns void to run .getTime(). That can't work.
This is what I use in JasperReports:
// Today
new java.util.Date().format('yyyy-MM-dd')
// Yesterday
new SimpleDateFormat("yyyy-MM-dd").format(new Date()-1)
// First Day of current month
new java.util.Date().format('yyyy') + "-" + new java.util.Date().format('MM') + "-01"
I prefer to use the ISO format YYYY-MM-DD because is recognized everywhere and avoid the regional formats confusion (dd/mm position on the date field).
//Yesterday (LocalDate)
java.time.LocalDate.now().minusDays(1)
//Yesterday (java.sql.Date)
java.sql.Date.valueOf( java.time.LocalDate.now().minusDays(1) )
//Yesterday (java.util.Date)
java.util.Date.from( java.time.LocalDate.now().minusDays(1).atStartOfDay(java.time.ZoneId.systemDefault()).toInstant() )
//First day of current month (LocalDate)
java.time.LocalDate.now().withDayOfMonth(1)
//First day of current month (java.sql.Date)
java.sql.Date.valueOf( java.time.LocalDate.now().withDayOfMonth(1) )
//First day of current month (java.util.Date)
java.util.Date.from( java.time.LocalDate.now().withDayOfMonth(1).atStartOfDay(java.time.ZoneId.systemDefault()).toInstant() )
I basically want to be able to show tomorrows date
I have this which shows today date
private Date date = new Date();
i tried this but this gave me jan 1 1970
private Date date = new Date(+1);
please help
The integer (actually long) parameter for the Date constructor is for specifying the milliseconds of offset from January 1st, 1970, GMT.
You need to use a Calendar instead
Calendar cal = Calendar.getInstance();
cal.add(Calendar.DATE, 1);
Date date = cal.getTime();
Note, the Date.setBlah and Date.getBlah methods are deprecated, Calendar should be used instead. (Not sure if that's available in J2ME though.)
private Date date = new Date();
date.setDate(date.getDate() + 1);
As suggested here, use an implementation of class Calendar like thus:
Calendar myCalendar = Calendar.getInstance();
long tomorrow = myCalendar.getTimeInMillis() + 24 * 60 * 60 * 1000;
myCalendar.setTimeInMillis(tomorrow);
And do whatever you want with that...
Hope this helps,
Yuval =8-)