How can I add business days to the current date in Java?

Question

How can I add business days to the current date in Java?

public Calendar addBusinessDate(Calendar cal, int days) {
//
// code goes over here
//
}


        

Answer 1

Most of the answer I've found online didn't work as expected, so I tweaked an example on this thread, How to get current date and add five working days in Java. The code below appears to work better.

public static Date addWorkingDays(Date date, int days) {
    if (days > 0) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);

        int daysAdded = 0;
        do {
            cal.add(Calendar.DATE, 1);
            if (isWorkingDay(cal)) {
                daysAdded++;
            }
        } while (daysAdded < days);

        return cal.getTime();;
    } else {
        return date;
    }
}


 private static boolean isWorkingDay(Calendar cal) {
    int dayOfWeek = cal.get(Calendar.DAY_OF_WEEK);
    if (dayOfWeek == Calendar.SUNDAY || dayOfWeek == Calendar.SATURDAY)
        return false;
    // tests for other holidays here        
    return true;
 }

Answer 2

tl;dr

Going forward.

myLocalDate.with( 
    org.threeten.extra.Temporals.nextWorkingDay() 
)

Going backward.

myLocalDate.with( 
    org.threeten.extra.Temporals.previousWorkingDay() 
)

Using java.time

The Question and other Answers use the troublesome old date-time classes, now legacy, supplanted by the java.time classes.

Also, see my Answer to a similar Question.

TemporalAdjuster

In java.time, the TemporalAdjuster interface provides for classes to manipulate date-time values. Using immutable objects, a new instance is created with values based on the original.

nextWorkingDay

The ThreeTen-Extra project extend java.time with additional functionality. That includes a nextWorkingDay adjuster that skips over Saturday and Sunday days. So we can loop, incrementing a date one day at a time, and skip over any weekend days.

The LocalDate class represents a date-only value without time-of-day and without time zone.

LocalDate start = LocalDate.now( ZoneId.of( "America/Montreal" ) ) ;
int businessDaysToAdd = 13 ;
// … ensure that: ( businessDaysToAdd >= 0 )

int daysLeft = businessDaysToAdd ;
LocalDate localDate = start ;
while ( daysLeft > 0 ) {
    localDate = localDate.with( Temporals.nextWorkingDay() );
    daysLeft = ( daysLeft - 1 ) ;  // Decrement as we go.
}
return localDate ;

Holidays

Holidays are an entirely different matter. Obviously there is no simple solution. You must either supply a list of your honored holidays, or obtain a list with which you agree.

Once you have such a list, I suggest writing your own implementation of TemporalAdjuster similar to nextWorkingDay.

---

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

• Java SE 8 and SE 9 and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Answer 3

Will this work? Of course, this is not handling holidays.

public static Date addBusinessDays(Date baseDate, int numberOfDays){

    if(baseDate == null){
        baseDate = new Date();
    }

    Calendar baseDateCal = Calendar.getInstance();
    baseDateCal.setTime(baseDate);

    for(int i = 0; i < numberOfDays; i++){

        baseDateCal.add(Calendar.DATE,1);
        if(baseDateCal.get(Calendar.DAY_OF_WEEK)
                         == Calendar.SATURDAY){
           baseDateCal.add(Calendar.DATE,2);
        }
    }
    return baseDateCal.getTime();
}

Answer 4

public static Date addBusinessDays(Date date, int days) {

    DateTime result = new DateTime(date);
    result = isWeekEnd(result)
        ? getPreviousBusinessDate(result)
        : result;

    for (int i = 0; i < days; i++) {
        if (isWeekEnd(result)) {
            i--;
        }
        result = result.plusDays(1);
    }
    return result.toDate();
}

private static boolean isWeekEnd(DateTime dateTime) {
    int dayOfWeek = dateTime.getDayOfWeek();
    return dayOfWeek == DateTimeConstants.SATURDAY || dayOfWeek == DateTimeConstants.SUNDAY;
}

private static DateTime getPreviousBusinessDate(DateTime result) {
    while (isWeekEnd(result)) {
        result = result.minusDays(1);
    }

    return result;
}

Answer 5

O(1) version that works and supports different weekend patterns and negative days:

import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

public class DateUtil {

//Weekend patterns
public static  final int WEEKEND_SAT_SUN = 0;
public static  final int WEEKEND_FRI_SAT = 1;
public static  final int WEEKEND_THU_FRI = 2;
public static  final int WEEKEND_FRI_SUN = 3;
public static  final int WEEKEND_FRI = 4;
public static  final int WEEKEND_SAT = 5;
public static  final int WEEKEND_SUN = 6;


//Weekend pattern by country 
//@see https://en.wikipedia.org/wiki/Workweek_and_weekend
public static Map<String,Integer> weekendPatternByCountry = new HashMap<>();
static {
    weekendPatternByCountry.put("CO",WEEKEND_SUN);     //Colombia
    weekendPatternByCountry.put("GQ",WEEKEND_SUN);     //Equatorial Guinea
    weekendPatternByCountry.put("IN",WEEKEND_SUN);     //India
    weekendPatternByCountry.put("MX",WEEKEND_SUN);     //Mexico
    weekendPatternByCountry.put("KP",WEEKEND_SUN);     //North Korea
    weekendPatternByCountry.put("UG",WEEKEND_SUN);     //Uganda
    weekendPatternByCountry.put("BN",WEEKEND_FRI_SUN); //Brunei Darussalam
    weekendPatternByCountry.put("DJ",WEEKEND_FRI);     //Djibouti
    weekendPatternByCountry.put("IR",WEEKEND_FRI);     //Iran
    weekendPatternByCountry.put("AF",WEEKEND_THU_FRI); //Afghanistan
    weekendPatternByCountry.put("NP",WEEKEND_SAT);     //Nepal
    weekendPatternByCountry.put("DZ",WEEKEND_FRI_SAT); //Algeria
    weekendPatternByCountry.put("BH",WEEKEND_FRI_SAT); //Bahrain
    weekendPatternByCountry.put("BD",WEEKEND_FRI_SAT); //Bangladesh
    weekendPatternByCountry.put("EG",WEEKEND_FRI_SAT); //Egypt
    weekendPatternByCountry.put("IQ",WEEKEND_FRI_SAT); //Iraq
    weekendPatternByCountry.put("IL",WEEKEND_FRI_SAT); //Israel
    weekendPatternByCountry.put("JO",WEEKEND_FRI_SAT); //Jordan
    weekendPatternByCountry.put("KW",WEEKEND_FRI_SAT); //Kuwait
    weekendPatternByCountry.put("LY",WEEKEND_FRI_SAT); //Libya
    weekendPatternByCountry.put("MV",WEEKEND_FRI_SAT); //Maldives
    weekendPatternByCountry.put("MR",WEEKEND_FRI_SAT); //Mauritania
    weekendPatternByCountry.put("MY",WEEKEND_FRI_SAT); //Malaysia
    weekendPatternByCountry.put("OM",WEEKEND_FRI_SAT); //Oman
    weekendPatternByCountry.put("PS",WEEKEND_FRI_SAT); //Palestine
    weekendPatternByCountry.put("QA",WEEKEND_FRI_SAT); //Qatar
    weekendPatternByCountry.put("SA",WEEKEND_FRI_SAT); //Saudi Arabia
    weekendPatternByCountry.put("SD",WEEKEND_FRI_SAT); //Sudan
    weekendPatternByCountry.put("SY",WEEKEND_FRI_SAT); //Syria
    weekendPatternByCountry.put("AE",WEEKEND_FRI_SAT); //United Arab Emirates
    weekendPatternByCountry.put("YE",WEEKEND_FRI_SAT); //Yemen
}

//Adjustment vectors - precomputed adjustment
static int[][][] adjVector = new int[][][]{
    {//WEEKEND_SAT_SUN
        //Positive number of days
        {1,0,-1,-2,-3,1,1},
        {0,0},
        {0,0,0,0,0,2,1},
        //Negative number of days
        {-1,3,2,1,0,-1,-1},
        {0,0},
        {-1,1,1,1,1,1,0}
    },
    {//WEEKEND_FRI_SAT
        //Positive number of days
        {0,-1,-2,-3,1,1,1},
        {0,0},
        {0,0,0,0,2,1,0},
        //Negative number of days
        {3,2,1,0,-1,-1,-1},
        {0,0},
        {1,1,1,1,1,0,-1}
    },
    {//WEEKEND_THU_FRI
        //Positive number of days
        {-1,-2,-3,1,1,1,0},
        {0,0},
        {0,0,0,2,1,0,0},
        //Negative number of days
        {2,1,0,-1,-1,-1,3},
        {0,0},
        {1,1,1,1,0,-1,1}
    },
    {//WEEKEND_FRI_SUN
        //Positive number of days
        {0,-1,-2,-3,-4,-4,0},
        {1,0},
        {0,0,0,0,0,-1,1},
        //Negative number of days
        {4,3,2,1,0,0,4},
        {0,-1},
        {1,1,1,1,1,0,2}
    },
    {//WEEKEND_FRI
        //Positive number of days
        {-1,-2,-3,-4,1,1,0},
        {0},
        {0,0,0,0,1,0,0},
        //Negative number of days
        {3,2,1,0,-1,-1,4},
        {0},
        {1,1,1,1,1,0,1}
    },
    {//WEEKEND_SAT
        //Positive number of days
        {0,-1,-2,-3,-4,1,1},
        {0},
        {0,0,0,0,0,1,0},
        //Negative number of days
        {4,3,2,1,0,-1,-1},
        {0},
        {1,1,1,1,1,1,0}
    },
    {//WEEKEND_SUN
        //Positive number of days
        {1,0,-1,-2,-3,-4,1},
        {0},
        {0,0,0,0,0,0,1},
        //Negative number of days
        {-1,4,3,2,1,0,-1},
        {0},
        {0,1,1,1,1,1,1}
    }
};

//O(1) algorithm to add business days.
public static Date addBusinessDays(Date day, int days,int weekendPattern){
    Calendar ret = Calendar.getInstance();
    if(day != null) {
        ret.setTime(day);
    }
    if(days != 0) {
        int startDayofWeek  = ret.get(Calendar.DAY_OF_WEEK)-1; //Zero based to use the vectors bellow.
        int idx = days > 0 ? 0 : 3;
        int howManyWeekendDays = 0;
        int[][] adjV = adjVector[weekendPattern];
        int numWeekendDaysInOneWeek = adjV[idx+1].length;

        for(int i  = 0; i < numWeekendDaysInOneWeek;i++){
            int adjustmentA = adjV[idx][startDayofWeek];  //pattern shift
            int adjustmentB = adjV[idx+1][i];             //day shift

            howManyWeekendDays += (days-adjustmentA-adjustmentB)/(7-numWeekendDaysInOneWeek); 
        }

        int adjustmentC = adjV[idx+2][startDayofWeek]; //f(0) adjustment
        howManyWeekendDays += adjustmentC;

        ret.add(Calendar.DATE,days + howManyWeekendDays);

        //TODO: Extend to support holidays using recursion
        // int numHolidays = getNumHolidaysInInterval(day,ret.getTime());
        // if(numHolidays > 0) return addBusinessDays(ret.getTime,numHolidays);
    }
    return ret.getTime();
}

public static Date addBusinessDays(Date day, int days,String country){
    Integer weekpat = weekendPatternByCountry.get(country);     
    return weekpat != null ? addBusinessDays(day,days,weekpat) : addBusinessDays(day,days,WEEKEND_SAT_SUN);
}
}

Answer 6

Here is the modified version to find date calculation.

public  Calendar algorithm2(int businessDays){
    Calendar cal2 = Calendar.getInstance();
    Calendar cal = Calendar.getInstance(); 
    int totalDays= businessDays/5*7;
    int remainder = businessDays % 5;
    cal2.add(cal2.DATE, totalDays); 

    switch(cal.get(Calendar.DAY_OF_WEEK)){
        case 1:
                break;
        case 2: 
                break;
        case 3: 
                if(remainder >3)
                cal2.add(cal2.DATE,2);
                break;
        case 4: 
                if(remainder >2)
                cal2.add(cal2.DATE,2);
                break;
        case 5: 
                if(remainder >1)
                cal2.add(cal2.DATE,2);
                break;
        case 6: 
                if(remainder >1)
                cal2.add(cal2.DATE,2);
                break;
        case 7: 
                if(remainder >1)
                cal2.add(cal2.DATE,1);
                break;
    }

    cal2.add(cal2.DATE, remainder); 
    return cal2;

}