How to add Days to a Date in Java with code samples
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Very often, when programmers perform date manipulation, they are required to add a specified number of days to a given date. In this article, we will learn how to add days to a Date in Java.
Using LocalDate
The LocalDate class makes it very easy to add days to a Date. Let us take a look at a few examples.
Adding days to a LocalDate
The following code sample demonstrates adding days to a LocalDate:
LocalDate date1 = LocalDate.of(2018, 05, 10);
System.out.println("Before adding days:"+date1);
LocalDate date2 = date1.plusDays(6);
System.out.println("After adding days:"+date2);
So in this case, the code above invokes the LocalDate.plusDays method. This adds the specified number of days to the LocalDate object on which it is invoked and returns and updated LocalDate.
So, this code prints the following output:
Before adding days:2018-05-10 After adding days:2018-05-16
Similarly, the LocalDate class has a minusDays method, that subtracts the specified number of days from a LocalDate object. The following code demonstrates this method:
LocalDate date1 = LocalDate.of(2018, 05, 10);
System.out.println("Before adding days:"+date1);
LocalDate date2 = date1.minusDays(6);
System.out.println("After adding days:"+date2);
This code prints the following output:
Before adding days:2018-05-10 After adding days:2018-05-04
Adding/Subtracting other components
Similarly, the LocalDate class has other methods that can be used to add/subtract months, years, weeks from a LocalDate. The following code demonstrates some of these methods:
LocalDate date1 = LocalDate.of(2018, 05, 10);
System.out.println("Before adding months:"+date1);
System.out.println("After adding 5 months:"+date1.plusMonths(5));
System.out.println("After substracting 4 months:"+date1.minusMonths(4));
System.out.println("After adding 2 weeks:"+date1.plusWeeks(2));
System.out.println("After substracting 1 week:"+date1.minusWeeks(1));
System.out.println("After adding 6 years:"+date1.plusYears(6));
System.out.println("After substracting 5 years:"+date1.minusYears(5));
This code prints the following output:
Before adding months:2018-05-10 After adding 5 months:2018-10-10 After substracting 4 months:2018-01-10 After adding 2 weeks:2018-05-24 After substracting 1 week:2018-05-03 After adding 6 years:2024-05-10 After substracting 5 years:2013-05-10
Using the Calendar/Date class
LocalDate is a new class added by Java 8. However, if you have legacy code, there are chances that this code might be using the java.util.Date or java.util.Calendar classes. Let us now take a look at what it takes to add a number of days to a Date represented using one of these classes.
Adding a number of days to a Calendar instance
The following code demonstrates adding days to a Date represented as a Calendar instance:
String strDate = "2018-05-10";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Calendar cal = Calendar.getInstance();
cal.setTime(sdf.parse(strDate));
System.out.println("Before adding days:"+cal.getTime());
cal.add(Calendar.DAY_OF_MONTH, 6);
System.out.println("After adding 6 days:"+cal.getTime());
So in this case, the code above first creates a Calendar instance corresponding to a Date in String format. It then invokes the add method. This adds 6 days to the DAY_OF_MONTH field.
This code displays the following output:
Before adding days: Thu May 10 00:00:00 IST 2018 After adding 6 days: Wed May 16 00:00:00 IST 2018
Adding a number of days to a Date instance
In order to add a number of days to a java.util.Date instance, you need to convert it to Calendar and use the same code as above. The following code demonstrates this:
String strDate = "2018-05-10";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date = sdf.parse(strDate);
Calendar cal = Calendar.getInstance();
cal.setTime(date);
System.out.println("Before adding days:"+cal.getTime());
cal.add(Calendar.DAY_OF_MONTH, 6);
Date newDate = cal.getTime();
System.out.println("After adding 6 days:"+newDate);
The code above first creates a Date object. It then converts it to a Calendar object cal and invokes the add method on it. This code produces the same output as before.
Further Reading
Conclusion
In this article, we saw how to add days to a date in Java.