Get week number for any given date

Question

How to get a week number in Java?

Answer 1

/ ====================================================
Method: Get the desired Date format for the date
Developed By: Sandip Waghole [29-Jan-2010]
==================================================== /
public String getWeekNo(String strDate)
// input Date Format : M/dd/yyyy
int weekNo=0,i=0;
String strWeekNo=null;
int noOfDaysInTheYear=365;
int WEEK_STARTS_ON = 1; // Define the day on which week starts Sunday/Monday 1:Sunday 2:Monday
int firstDayNoInFirstWeekOfPresentYear=0; // Inititalize teh day on which week is starting in present year
int firstDayOfPresentYear=0; // Inititlize the 1st day of the present year whether Sunday/Monday/.....
int[] monthDaysArray = {31,28,31,30,31,30,31,31,30,31,30,31}; // Define array of the days as per months
int todaysDayNoInPresentYear=0;
int daysLateByFirstWeekStartedAfterYearStarted=0;
int intTemp=0;
//strDate="08/24/2000"; // For test purpose
StringTokenizer strDateTok = new StringTokenizer(strDate, "/ ");
int month = Integer.parseInt(strDateTok.nextToken());
int day= Integer.parseInt(strDateTok.nextToken());
int year = Integer.parseInt(strDateTok.nextToken());
GregorianCalendar cal = new GregorianCalendar();
// Check if present year is leap year
boolean boolIsLeapYear = cal.isLeapYear(year);
// If it is boolean year then add 1 to total days in the year & add one more day to february
if(boolIsLeapYear)
noOfDaysInTheYear=noOfDaysInTheYear+1;
monthDaysArray[1]=monthDaysArray[1]1;
// Find the 1st day of this year
Calendar calObj = new GregorianCalendar(year, Calendar.JANUARY, 1);
firstDayOfPresentYear = calObj.get(Calendar.DAY_OF_WEEK);
int intRemoveNoOfDaysFromWeek=0;
// # Find the day no of prsent day
for(i=0;i<month;i+) // get no of days till present year
intTemp = intTemp monthDaysArray;
todaysDayNoInPresentYear = intTemp - (monthDaysArray[month-1]-day);
if(firstDayOfPresentYear==6 || firstDayOfPresentYear==7) // If first Day is Friday or Saturday then it is week
// Identify the the day no on which 1st week of present year is starting
firstDayNoInFirstWeekOfPresentYear = 7 - firstDayOfPresentYear WEEK_STARTS_ON 1;
// Find delay in the 1st week start after r=the year start
daysLateByFirstWeekStartedAfterYearStarted = firstDayNoInFirstWeekOfPresentYear - 1;
// Now week is starting from Sunday
weekNo = (Integer)((todaysDayNoInPresentYear-daysLateByFirstWeekStartedAfterYearStarted)/7);
// Find the day no of today
intTemp = (todaysDayNoInPresentYear-daysLateByFirstWeekStartedAfterYearStarted) % 7;
if(intTemp > 0)
weekNo=weekNo+1;
else
weekNo=weekNo;
else
// 1st week is starting on 1st Of January
firstDayNoInFirstWeekOfPresentYear=firstDayOfPresentYear;
// Remove no. of days from the 1st week as week is starting from odd Sunday/Monday/Tuesday/Wednesday/Thursday
intRemoveNoOfDaysFromWeek = 7-firstDayOfPresentYear 1; // 1 added as include start day also
// So one week will be added in no. of weeks
weekNo = (Integer)((todaysDayNoInPresentYear-intRemoveNoOfDaysFromWeek)/7);
// Find the day no of today
intTemp = (todaysDayNoInPresentYear-intRemoveNoOfDaysFromWeek) % 7;
weekNo = weekNo +1; // As 1st weeks days are reduced from the todays day no in the year
if(intTemp > 0)
weekNo=weekNo+1;
else
weekNo=weekNo;
// Remove the no. of days from the week 1
strWeekNo=Integer.toString(weekNo);
return strWeekNo;
// Any issues please mail on [email protected]