.roll()

The .roll() method for the Calendar class can be used to add or subtract a single unit of time on the given calendar without changing the larger fields.

Syntax

calendar.roll(calndr_field, bool_flag)

This method takes two arguments, calndr_field, which will be used to select which field of the calendar you will use (YEAR, MONTH, DAY). The second one bool_flag will add a single unit of time if true or will subtract a single unit of time if false.

Example

In the following example, .roll() is being used to add and subtract one year to the calendar being used.

import java.util.*;

public class roll_method {
  public static void main(String args[]) {

    // Creating a calendar.
    Calendar calndr = Calendar.getInstance();

    // Current Year.
    System.out.println("The Current Year is: " + calndr.get(Calendar.YEAR));

    // false will decrement the year by subtracting a single unit of time.
    calndr.roll(Calendar.YEAR, false);

    // Showing year after operation.
    System.out.println("The New Year is: " + calndr.get(Calendar.YEAR));

    // true will increment the year by adding a single unit of time.
    calndr.roll(Calendar.YEAR, true);

    // Showing year after operation.
    System.out.println("The New Year is: " + calndr.get(Calendar.YEAR));
  }
}

The output of the above code will be similar to the following:

The Current Year is: 2023
The New Year is: 2022
The New Year is: 2023