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Get start date and end date from week/month/year

I need to extract the start date and end date from a given year and week and return them as LocalDate:
Example: year / month / week : 2022 / 12 / 49 -> date_begin 05/12/2022 - date_end 11/12/2022 this mean the week 49 of the year 2022 starts from 05/12/2022 and ends on the 11/12/2022. The month is irrelevant, as #rzwitserloot said in the comments. The input is provided in ints int year = 2022 and int week = 49.
How to achieve this?

JSR310-extra had the YearWeek, but the somewhat simpler java.time does not - hence, the simplest way is through the parser even if you don't actually need to parse it:
int weekYear = 2022;
int weekNum = 49;
LocalDate monday = LocalDate.parse(String.format("%04d-W%02d-1", weekYear, weekNum), DateTimeFormatter.ISO_WEEK_DATE);
LocalDate sunday = monday.plusDays(6);
System.out.printf("Week %d of year %d runs from %s to %s\n", weekNum, weekYear, monday, sunday);
NB: The format is e.g. 2022-W49-1; the 1 is for 'monday'. Note that this is weekyears: That means the start date could be in the previous year (e.g. week 1 of certain years starts on december 30th in the previous year), or the end date could be in the next year. This is obvious if you think about it (weeks exist that start in one year and end in the next, and they have to be part of some year's 'week-year' system). Just thought I'd highlight it :)

This solution also works
import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.WeekFields;
public class Main {
public static final WeekFields US_WEEK_FIELDS = WeekFields.of(DayOfWeek.SUNDAY, 4);
public static void main(String[] args) {
LocalDate date1 = LocalDate.of(2022, 12, 29);
LocalDate date2 = LocalDate.now();
System.out.println(formatDate(date1));
System.out.println(formatDate(date2));
}
public static int getWeek(LocalDate date) {
return date.get(US_WEEK_FIELDS.weekOfWeekBasedYear());
}
public static int getMonth(LocalDate date) {
return date.getMonthValue();
}
public static int getYear(LocalDate date) {
return date.get(US_WEEK_FIELDS.weekBasedYear());
}
public static String formatDate(LocalDate date) {
int week = getWeek(date);
int month = getMonth(date);
int year = getYear(date);
return year + "/" + month + "/" + week;
}
}
When running I get in the console
2022/12/52
2022/12/49

Java - Generate Random DOB [duplicate]

This question already has answers here:
How can I pad an integer with zeros on the left?
(18 answers)
Adding zero to a single digit number, Is it possible?
(2 answers)
Generate random date of birth
(15 answers)
Closed 5 years ago.
I want to generate random DOB for the given range of year. So I tried the below code
private static String randomDataOfBirth(int yearStart, int yearEnd)
{
GregorianCalendar gc = new GregorianCalendar();
int year = randBetween(yearStart, yearEnd);
gc.set(Calendar.YEAR, year);
int dayOfYear = randBetween(1, gc.getActualMaximum(Calendar.DAY_OF_YEAR));
gc.set(Calendar.DAY_OF_YEAR, dayOfYear);
String date = null;
if(gc.get(Calendar.MONTH) == 0)
{
date = gc.get(Calendar.YEAR) + "-" + 1 + "-" + gc.get(Calendar.DAY_OF_MONTH);
}else
{
date = gc.get(Calendar.YEAR) + "-" + gc.get(Calendar.MONTH) + "-" + gc.get(Calendar.DAY_OF_MONTH);
}
return date;
}
private static int randBetween(int start, int end) {
// TODO Auto-generated method stub
return start + (int)Math.round(Math.random() * (end - start));
}
Main:-
public static void main(String[] args) {
String dob = randomDataOfBirth(1899, 1937);
System.out.println(dob);
}
I can be able to generate the random DOB. But only for the Month and Day, I want to add a prefix '0' for the range from 1 to 9
Month - 01, 02, 03 and ... up to 09
Day - 01, 02, 03 and ... up to 09

Apart from the desired formatting of you date I see some other problems with your code that I think you would want to address:
Assuming you want a usual month number, 01 for January through 12 for December, your handling of the month number is not correct. get(Calendar.MONTH) gives you a 0-based month: 0 for January through 11 for December. Therefore, your code not only will never give you 12 as month and 1 all too often. It will also give you non-existing dates. I have seen 1905-2-31 and 1929-4-31 (because you get 2 for March, which we interpret as February, etc.).
Possibly unimportant, your distribution gives each day in a leap year slightly smaller probablity than other days.
If you can, I suggest you use LocalDate. The class was introduced in Java 8:
private static String randomDataOfBirth(int yearStartInclusive, int yearEndExclusive) {
LocalDate start = LocalDate.ofYearDay(yearStartInclusive, 1);
LocalDate end = LocalDate.ofYearDay(yearEndExclusive, 1);
long longDays = ChronoUnit.DAYS.between(start, end);
int days = (int) longDays;
if (days != longDays) {
throw new IllegalStateException("int overflow; too many years");
}
int day = randBetween(0, days);
LocalDate dateOfBirth = start.plusDays(day);
return dateOfBirth.toString();
}
This gives you evenly distributed, correct dates formatted with 2 digits for month and day-of-month, e.g., 1926-07-05.
If you want to avoid the overflow check, you may of course rewrite your randBetween() to handle longs.
If you cannot use Java 8, you can do something similar with GregorianCalendar and SimpleDateFormat. Counting the exact number of days from lower to upper bound is complicated, though, so you will probably want to stick to your way of picking the date. SimpleDateFormat can still give you correct dates formatted with two digits for month and day. Edit: In your class, declare:
static DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
Now just substitute your if-else statement with this:
String date = formatter.format(gc.getTime());
If your randomDataOfBirth() may be accessed from more than one thread, this won’t work since SimpleDateFormat is not thread-safe. If so, each thread should have its own SimpleDateFormat instance.

With Java7 you can try with something like this:
public class DobMaker
{
public String getDOB(int min, int max)
{
Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
int year = min + new Random().nextInt(max - min + 1);
calendar.set(Calendar.YEAR, year);
int day = 1+new Random().nextInt(calendar.getActualMaximum(Calendar.DAY_OF_YEAR));
calendar.set(Calendar.DAY_OF_YEAR, day);
return new SimpleDateFormat("yyyy-MM-dd").format(calendar.getTime());
}
public static void main(String[] args)
{
DobMaker d = new DobMaker();
System.out.println(d.getDOB(1970, 1980));
System.out.println(d.getDOB(1970, 1971));
System.out.println(d.getDOB(2007, 2016));
}
}

Java8 java.time: how to change the day of the week and the start time of the day?

Say I want my week to start on Tuesday, and the day should start at 5:30 am.
This means, code like this should work:
// LocalDateTimes created with the "standard" ISO time
LocalDateTime tuesday_4_30 = LocalDateTime.now()
.with(TemporalAdjusters.next(DayOfWeek.TUESDAY))
.withHour(4).withMinute(30);
LocalDateTime tuesday_6_30 = tuesday_4_30.withHour(6).withMinute(30);
LocalDateTime previous_monday = tuesday_4_30.minusDays(1);
// eventual adjustment using TemporalAdjusters here? like this?
// tuesday_4_30 = tuesday_4_30.with(new MyTemporalAdjuster(DayOfWeek.TUESDAY, 5, 30));
// <do the same for 6_30 and previous monday>
// or possibly change some global parameter like Chronology, Locale, or such..
Assert.assertEquals(tuesday_4_30.getDayOfWeek(), DayOfWeek.MONDAY);
Assert.assertEquals(tuesday_6_30.getDayOfWeek(), DayOfWeek.TUESDAY);
// there is 1 week between the previous monday and the next tuesday 6:30
Assert.assertEquals( ChronoUnit.WEEKS.between(previous_monday,tuesday_6_30), 1);
// there is 0 week between the previous monday and the next tuesday 4:30
Assert.assertEquals( ChronoUnit.WEEKS.between(previous_monday,tuesday_4_30), 0);
// 1 day between tuesday_4_30 and tuesday_6_30
Assert.assertEquals( ChronoUnit.DAYS.between(tuesday_4_30,tuesday_6_30), 1);
// 0 day between previous_monday and tuesday_4_30
Assert.assertEquals( ChronoUnit.DAYS.between(previous_monday,tuesday_4_30), 1);
I am tempted to use temporal adjusters here, and I'm quite sure I could offset the hours and minute so that the day starts at 5:30, but I can't figure out how to modify the start of the week.
Note that I looked into WeekFields but I can't make it work with ChronoUnit.XXX.between(), so I didn't go too far. It looks like I would have to code my own Chronology, which seemed too far strectched.
Can you help me?

Note: ChronoUnit.WEEKS.between counts the number of entire weeks (a period of 7 days) between two dates. In your case, there is only one days between the Monday and the Tuesday so it will return 0. You probably meant to compare the week of year fields instead.
Unless you want to write your own chronology (that's going to be a pain), you could "fake" your calendar by:
converting back and forth between UTC and UTC+5:30 to represent your cut-off time / or just subtract 5:30 from the dates
adding some simple logic for the week calculations
See below a rough example based on your code, that makes all the tests pass - you may want to extract the logic into a separate class etc. This is a bit hacky but may be enough for your use case.
#Test
public void test() {
LocalDateTime tuesday_4_30 = LocalDateTime.now()
.with(TemporalAdjusters.next(DayOfWeek.TUESDAY))
.withHour(4).withMinute(30);
LocalDateTime tuesday_6_30 = tuesday_4_30.withHour(6).withMinute(30);
LocalDateTime previous_monday = tuesday_4_30.minusDays(1);
// eventual adjustment using TemporalAdjusters here? like this?
// tuesday_4_30 = tuesday_4_30.with(new MyTemporalAdjuster(DayOfWeek.TUESDAY, 5, 30));
// <do the same for 6_30 and previous monday>
// or possibly change some global parameter like Chronology, Locale, or such..
assertEquals(dayOfWeek(tuesday_4_30), DayOfWeek.MONDAY);
assertEquals(dayOfWeek(tuesday_6_30), DayOfWeek.TUESDAY);
// there is 1 week between the previous monday and the next tuesday 6:30
assertEquals(weekBetween(previous_monday, tuesday_6_30), 1);
// there is 0 week between the previous monday and the next tuesday 4:30
assertEquals(weekBetween(previous_monday, tuesday_4_30), 0);
// 1 day between tuesday_4_30 and tuesday_6_30
assertEquals(weekBetween(tuesday_4_30, tuesday_6_30), 1);
// 0 day between previous_monday and tuesday_4_30
assertEquals(weekBetween(previous_monday, tuesday_4_30), 0);
}
private static DayOfWeek dayOfWeek(LocalDateTime date) {
return date.atOffset(ZoneOffset.ofHoursMinutes(5, 30)).withOffsetSameInstant(UTC).getDayOfWeek();
}
private static int weekBetween(LocalDateTime date1, LocalDateTime date2) {
OffsetDateTime date1UTC = date1.atOffset(ZoneOffset.ofHoursMinutes(5, 30)).withOffsetSameInstant(UTC);
OffsetDateTime date2UTC = date2.atOffset(ZoneOffset.ofHoursMinutes(5, 30)).withOffsetSameInstant(UTC);
int w1 = date1UTC.get(IsoFields.WEEK_OF_WEEK_BASED_YEAR);
if (dayOfWeek(date1).getValue() >= TUESDAY.getValue()) w1++;
int w2 = date2UTC.get(IsoFields.WEEK_OF_WEEK_BASED_YEAR);
if (dayOfWeek(date2).getValue() >= TUESDAY.getValue()) w2++;
return w2 - w1;
}
Alternative implementation, maybe cleaner:
private static DayOfWeek dayOfWeek(LocalDateTime date) {
return adjust(date).getDayOfWeek();
}
private static int weekBetween(LocalDateTime date1, LocalDateTime date2) {
int w1 = adjust(date1).get(IsoFields.WEEK_OF_WEEK_BASED_YEAR);
if (dayOfWeek(date1).getValue() >= TUESDAY.getValue()) w1++;
int w2 = adjust(date2).get(IsoFields.WEEK_OF_WEEK_BASED_YEAR);
if (dayOfWeek(date2).getValue() >= TUESDAY.getValue()) w2++;
return w2 - w1;
}
private static LocalDateTime adjust(LocalDateTime date) {
return date.minusHours(5).minusMinutes(30);
}

joda time - add weekdays to date

Is it possible to add weekdays to joda time?
For instance, if current date is Friday 01/03, date + 1 should return Monday 04/03, rather than 02/03.

As far as I know there is no built-in method to automatically do this for you in Joda Time. However, you could write your own method, that increments the date in a loop until you get to a weekday.
Note that, depending on what you need it for exactly, this could be (much) more complicated than you think. For example, should it skip holidays too? Which days are holidays depends on which country you're in. Also, in some countries (for example, Arabic countries) the weekend is on Thursday and Friday, not Saturday and Sunday.

LocalDate newDate = new LocalDate();
int i=0;
while(i<days)//days == as many days as u want too
{
newDate = newDate.plusDays(1);//here even sat and sun are added
//but at the end it goes to the correct week day.
//because i is only increased if it is week day
if(newDate.getDayOfWeek()<=5)
{
i++;
}
}
System.out.println("new date"+newDate);

Be aware that iterating through adding N days one at a time can be relatively expensive. For small values of N and/or non performance sensitive code, this is probably not an issue. Where it is, I'd recommend minimizing the add operations by working out how many weeks and days you need to adjust by:
/**
* Returns the date that is {#code n} weekdays after the specified date.
* <p>
* Weekdays are Monday through Friday.
* <p>
* If {#code date} is a weekend, 1 weekday after is Monday.
*/
public static LocalDate weekdaysAfter(int n, LocalDate date) {
if (n == 0)
return date;
if (n < 0)
return weekdaysBefore(-n, date);
LocalDate newDate = date;
int dow = date.getDayOfWeek();
if (dow >= DateTimeConstants.SATURDAY) {
newDate = date.plusDays(8 - dow);
n--;
}
int nWeeks = n / 5;
int nDays = n % 5;
newDate = newDate.plusWeeks(nWeeks);
return ( (newDate.getDayOfWeek() + nDays) > DateTimeConstants.FRIDAY)
? newDate.plusDays(nDays + 2)
: newDate.plusDays(nDays);

public LocalDate getBusinessDaysAddedDate(LocalDate localDate, int businessDays){
LocalDate result;
if(localDate.getDayOfWeek().getValue() + businessDays > 5) {
result = localDate.plusDays(2);
}
result = localDate.plusDays(businessDays);
return result;
}
In order to work with Date instead of LocalDate, refer https://stackoverflow.com/a/47719540/12794444 for the conversions.

Class YearMonthDay is deprecated and you shouldn't use it. If you change to simple DateTime you can obtain the week day by calling:
dateTime.getDayOfWeek();
For Friday it will be 5.
One of the approaches can be making a custom addDays method which should look something like that:
addDays(DateTime dateTime, int days) {
for(int i=0;i<days;i++){
dateTime.plusDays(1);
if(dateTime.getDayOfWeek()==6) dateTime.plusDays(2); // if Saturday add 2 more days }
}

age calculation method doesnt return the correct age? [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How do I calculate someone's age in Java?
I want to calculate the user age , and my method doesnt give the correct age in case if the month of birth is equal to the current month and the day of birth less than or equal the current day ( if the user enter his birth date through the date picker as 9/4/1990 or 4/4/1990 the age will be 21 not 22) how i can solve this problem ? what is the update i should do to get the correct age in this case ? please help me ....
this is my method
public static String getAge(int year,int month,int day) {
Calendar dob = Calendar.getInstance();
Calendar today = Calendar.getInstance();
dob.set(year, month, day);
int age = today.get(Calendar.YEAR) - dob.get(Calendar.YEAR);
if (today.get(Calendar.DAY_OF_YEAR) < dob.get(Calendar.DAY_OF_YEAR)){
age--;
}
Integer ageInt = new Integer(age);
String ageS = ageInt.toString();
return ageS;
}

There are two problems with your code:
if the date of birth is 9th April 1990, you need to write dob.set(1990,3,9) as months start at 0 ==> you probably need dob.set(year, month - 1, day);
if the current year is a leap year and not the year of birth (or vice versa) and dates are after the 28/29 Feb, you will get 1 day difference on an identical date.
This seems to work but you should test it with various scenarios and make sure you are happy with the result:
public static String getAge(int year, int month, int day) {
Calendar dob = Calendar.getInstance();
Calendar today = Calendar.getInstance();
dob.set(year, month - 1, day);
int age = today.get(Calendar.YEAR) - dob.get(Calendar.YEAR);
if (today.get(Calendar.MONTH) < dob.get(Calendar.MONTH)) {
age--;
} else if(today.get(Calendar.MONTH) == dob.get(Calendar.MONTH)) {
if (today.get(Calendar.DAY_OF_MONTH) < dob.get(Calendar.DAY_OF_MONTH)) {
age--;
}
}
Integer ageInt = new Integer(age);
String ageS = ageInt.toString();
return ageS;
}
And a (very simplified) test:
public static void main(String[] args) { //today = 8 April 2012
System.out.println(getAge(1990,3,7)); //22
System.out.println(getAge(1990,3,8)); //22
System.out.println(getAge(1990,3,9)); //22
System.out.println(getAge(1990,4,7)); //22
System.out.println(getAge(1990,4,8)); //22
System.out.println(getAge(1990,4,9)); //21
System.out.println(getAge(1990,5,7)); //21
System.out.println(getAge(1990,5,8)); //21
System.out.println(getAge(1990,5,9)); //21
}

You can compute the difference by transforming both dates in milliseconds and than in a Date object for example. Code would be something like this:
long ageMilis = today.getTimeInMillis() - dob.getTimeInMillis();
Date age = new Date(ageMilis);
return age.toString();