Find all Business Days between Two Dates

Learn to find all business days between two given dates in Java. The business days are considered all weekdays, excluding all holidays falling on weekdays. Once we have a List of business dates, we can use the list.size() API to get the total count of business days.

The given examples take an optional holiday list and use two predicates to check if a day is a weekend or holiday.

Given both examples use these predicates:

• The first predicate isWeekend is used to check if a day is a weekend.
• The second predicate isHoliday checks if a given day is a holiday.

1. LocalDate.datesUntil() – Java 9

LocalDate.datesUntil() returns a stream of dates from the start date to the end date. We then check each date in the stream against our two predicates.

If the day is not a weekend or a holiday, we consider it a business day. We get all such dates and store them in a List using stream aggregation method collect().

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.ChronoUnit;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.function.Predicate;
import java.util.stream.Stream;

private static List<LocalDate> countBusinessDaysBetween_Java9(final LocalDate startDate,
        final LocalDate endDate,
        final Optional<List<LocalDate>> holidays) {

    // Validate method arguments
    if (startDate == null || endDate == null) {
        throw new IllegalArgumentException("Invalid method argument(s) 
            to countBusinessDaysBetween (" + startDate + "," + endDate + "," + holidays + ")");
    }

    // Predicate 1: Is a given date is a holiday
    Predicate<LocalDate> isHoliday = date -> holidays.isPresent()
                && holidays.get().contains(date);

    // Predicate 2: Is a given date is a weekday
    Predicate<LocalDate> isWeekend = date -> date.getDayOfWeek() == DayOfWeek.SATURDAY
            || date.getDayOfWeek() == DayOfWeek.SUNDAY;

    // Iterate over stream of all dates and check each day against any weekday or holiday
    List<LocalDate> businessDays = startDate.datesUntil(endDate)
            .filter(isWeekend.or(isHoliday).negate())
            .collect(Collectors.toList());

    return businessDays;
}

Now we can use List.size() method to get the number of business days, or we can use each date in the list the way we want.

2. Finding Business Days with Stream API

First, we will get the total number of days between two given dates using the ChronoUnit.DAYS.between() API.

Then we get iterate over a stream of all the dates from the start date to the end date, until we hit daysBetween limit, and check each date against our two predicates isHoliday and isWeekend.

private static List<LocalDate> countBusinessDaysBetween_Java8(final LocalDate startDate,
        final LocalDate endDate,
        final Optional<List<LocalDate>> holidays)
{
    // Validate method arguments
    if (startDate == null || endDate == null) {
        throw new IllegalArgumentException("Invalid method argument(s) to 
            countBusinessDaysBetween (" + startDate
            + "," + endDate + "," + holidays + ")");
    }

    // Predicate 1: Is a given date is a holiday
    Predicate<LocalDate> isHoliday = date -> holidays.isPresent() 
            && holidays.get().contains(date);

    // Predicate 2: Is a given date is a weekday
    Predicate<LocalDate> isWeekend = date -> date.getDayOfWeek() == DayOfWeek.SATURDAY
            || date.getDayOfWeek() == DayOfWeek.SUNDAY;

    // Get all days between two dates
    long daysBetween = ChronoUnit.DAYS.between(startDate, endDate);

    // Iterate over stream of all dates and check each day against any weekday or
    // holiday
    return Stream.iterate(startDate, date -> date.plusDays(1))
            .limit(daysBetween)
            .filter(isHoliday.or(isWeekend).negate())
            .collect(Collectors.toList());
}

Happy Learning !!

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