Oracle next_day function equivalent in JAVA

I wanted to make a method which works similar to as oracle's next_day() function, below is my code which accepts date n weekday in MONDAY,TUESDAY etc. and returns a date which falls on the next given day from the input date.

/**
 * @param date
 * @param weekDay
 * @return Gives the date for next weekday specified in the parameter.
 */    
public Date getNextDay(Date value, String weekday) {
    Calendar date1 = Calendar.getInstance();
    date1.setTime(value);
        
    if (weekday.equalsIgnoreCase("MONDAY"))	{
		while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY) {
			date1.add(Calendar.DATE, 1);
        }
	} else if (weekday.equalsIgnoreCase("TUESDAY")) {
		while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.TUESDAY) {
			date1.add(Calendar.DATE, 1);
        }
    } else if (weekday.equalsIgnoreCase("WEDNESDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.WEDNESDAY) {
        	date1.add(Calendar.DATE, 1);
        }
    } else if (weekday.equalsIgnoreCase("THURSDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.THURSDAY) {
        	date1.add(Calendar.DATE, 1);
        }
    } else if (weekday.equalsIgnoreCase("FRIDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.FRIDAY) {
			date1.add(Calendar.DATE, 1);
		}
	} else if (weekday.equalsIgnoreCase("SATURDAY")) {
		while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY) {
			date1.add(Calendar.DATE, 1);
		}
	} else {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) {
			date1.add(Calendar.DATE, 1);
		}
    }
        	    
    return date1.getTime();
}

Please suggest a better way of doing this.

I recommend you do it using the modern java.time date-time API. Learn more about the modern date-time API from Trail: Date Time. The java.util date-time API and SimpleDateFormat are outdated and error-prone. In case you are not using Java-8, you can still use Java-8 date-time API through ThreeTenABP library.

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;
public class Main {
public static void main(String[] args) {
// Tests
// Next occurrence
System.out.println(getNextDay(LocalDate.now(), "Monday"));
System.out.println(getNextDay(LocalDate.now(), "Wednesday"));
// Same (if date falls on the given day) or next occurrence
System.out.println(getSameOrNextDay(LocalDate.now(), "Monday"));
System.out.println(getSameOrNextDay(LocalDate.now(), "Wednesday"));
}
static LocalDate getNextDay(LocalDate value, String weekday) {
return value.with(TemporalAdjusters.next(DayOfWeek.valueOf(weekday.toUpperCase())));
}
static LocalDate getSameOrNextDay(LocalDate value, String weekday) {
return value.with(TemporalAdjusters.nextOrSame(DayOfWeek.valueOf(weekday.toUpperCase())));
}
}

Output:

2020-09-28
2020-09-30
2020-09-28
2020-09-23

If you are interested in the next day I'll suggest using a java.time.LocalDate instead of a java.util.Date.

The following code accepts such a LocalDate along with a String (that needs to be a full day of week in upper case letters) and returns the LocalDate representing the nearest future date which has the given day of week:

public static LocalDate nextDay(LocalDate sourceDay, String weekday) {
	// parse the day of week to an enum value
	DayOfWeek dayOfWeek = DayOfWeek.valueOf(weekday);
	// check if the day is the same as the one of the given LocalDate
	if (sourceDay.getDayOfWeek().equals(dayOfWeek)) {
		// and return the LocalDate that's a week later
		return sourceDay.plusWeeks(1);
	} else {
		// otherwise add a day to the given date
		LocalDate nextDayOfWeek = sourceDay.plusDays(1);
		// and do that until the day of week of the given date is reached
		while (nextDayOfWeek.getDayOfWeek() != dayOfWeek) {
			nextDayOfWeek = nextDayOfWeek.plusDays(1);
		}
		// then return the future date
		return nextDayOfWeek;
	}
}

You can use it in a main like this:

	public static void main(String[] args) {
		System.out.println(nextDay(LocalDate.now(), "FRIDAY")
							.format(DateTimeFormatter.ofPattern("uuuu-MM-dd '('EEEE')'",
									Locale.ENGLISH)));
	}

Output (today ⇒ 2020-09-23):

2020-09-25 (Friday)

Use the "new" java.time.DayOfWeek and java.time.LocalDate classes:

public LocalDate getNextDay(
    final LocalDate value,
    final DayOfWeek day
)
{
    int currentDay = value.getDayOfWeek().getValue();
    int expectedDay = day.getValue();
    if ( currentDay >= expectedDay )
    {
        expectedDay += 7;
    }
    return value.plusDays( expectedDay - currentDay );
}