How to get daterange from weeknumber of month and by knowing the year in Java?-CodePudding

I have data such as September2021W5, in which W5 is the week number of the month September2021. How do i get daterange i.e start date and end date of that particular week. Thanks in advance for any help provided.

CodePudding user response：

Build a DateTimeFormatter that uses a default day of week as needed (start of week, e.g. Monday).
Example:

var format = new DateTimeFormatterBuilder()
             .appendPattern("MMMMuuuu'W'W")   // or use corresponding appends
             .parseDefaulting(ChronoField.DAY_OF_WEEK, DayOfWeek.MONDAY.getValue())
             .toFormatter()
             .withLocale(Locale.US);
var date = LocalDate.parse("September2021W5", format);

same can be done for the end of the week, or just adding 6 days to previous result (date.plusDays(6))

MMMM is for month of year, full form
uuuu year
'W' for literal W
W for week of month

Using Locale.UK so the month gets parsed for that locale, use the one needed for the given input - to use the default system Locale, use Locale.getDefault().

CodePudding user response：

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.ChronoField;

public class HelloWorld
{
     public static void main(String []args)
     {
        // your input date
        LocalDate localDate = LocalDate.of(2022, 9, 30);

        // ensure week 5
        LocalDate week = localDate.with(ChronoField.ALIGNED_WEEK_OF_MONTH, 5);

        // get localDate for first and last day
        LocalDate start = week.with(DayOfWeek.MONDAY);
        LocalDate end = start.plusDays(6);
        System.out.println(start  " - "  end);
    }
}